Duration : 90 Minutes
Aquifer Thermal Energy Storage (ATES), considered as an energy saving system and sustainable energy technology, it is growing exponentially in the Netherlands. The principle of ATES system is to cold or heat when available and retrieve it or use when needed. The NL government wishes to stimulate this growth to diminish energy use and reduce emissions. However, because many urban city centres deal with contaminated soil and groundwater, more and more ATES ambitions are confronted with the presence of contaminants.
Chlorinated volatile organic compounds (VOCls) are by far the most prevalent organic contaminants in the subsurface throughout the world . Among these compounds, PCE, TCE cis-DCE and vinyl chloride (VC) are the main representatives . Since VOCls are potentially carcinogenic, especially VC has been classified by International Agency for Research on Cancer as a human carcinogen , their presence in groundwater is considered as a threat to public health.
Together with the concerns on toxic impacts, the removal of VOCls is of importance and necessary as well. Due to the recalcitrant nature of VOCls, they are among the most difficult contaminants to be cleaned up and characterised, especially when they exist as dense non aqueous-phase liquid (DNAPL). Therefore, conventional techniques such as pump-and-treat, soil vapour extraction and soil excavation are either too costly or inefficient to properly remediate VOCls contaminants, while bio-based techniques become more and more attractive, such as monitored natural attenuation and enhanced bioremediation . It is reported that remediation based on biological transformation and biodegradation with proper stimulation approaches can be an effective way to reduce organic contaminants . Hence a combination of natural attenuation and (bio)stimulation by existing engineering system, in this case ATES system, could a very promising integrated technique for remediation of VOCls.
Several factors are proved to be important for biological natural attenuation, which also apply in enhanced bioremediation of VOCls, included temperature, availability of electron donor and nutrients, redox conditions, presence of specific microorganisms and pH . When these conditions are suitable in the environment, VOCls can be biologically reduce to ethane completely . Such anaerobic process is called reductive dechlorination. However, natural reductive dechlorination is normally limited by one or more factors that mentioned above, resulting in no or incompletely biodegradation of VOCls in the subsurface. For instance, due to lack of “Dehalococcoides ethenogenes”, the only species that can perform full reduction of VOCls to ethene, often cis-DCE and VC accumulate in contaminated subsurface; and electron donor and extra pH most often should be added as part of an engineered bioremediation scheme to fulfil reductive dechlorination .
ATES as an engineered system that locate at similar depth in the subsurface where VOCls also present , could possibly change the environmental conditions for VOCls biodegradation, when ATES is used as a tool for bio-stimulation implementations. ATES is expected to highly influence the temperature and groundwater flow in the subsurface. Temperature is already known as a significant factor for the activities of microorganisms. The tolerance, metabolic activity of microorganisms, and interactions with other microorganisms are influenced by temperature. For biological systems, if rate-limited by enzyme activity, the conversion rates increase by a factor of 1.5 to 2.5, when the temperature of the system increases by 10°C . Moreover, the transport of large volume groundwater (ATES systems have a typical flow rate up to several hundred cubic meters of groundwater per hour) can alter other conditions in the subsurface. Generally seasonal change of groundwater flow direction could be simplified as a homogeneous and redistributive effect in the ATES area, especially on some important geochemical solutes like SO42-, NO3- and HCO3-, microorganism, dissolved organic carbons and nutrients, leading to larger biodegradation area. The enhanced dissolution effect on DNAPL could also be benefit for its bioavailability when ATES is located in DNAPL layers. The dissolution can as well reduce the toxic effect of DNAPL on microorganism. Therefore with proper designs and operation, ATES can be further used to apply bioaugmentation or chemical injection and implemented to stimulate bioremediation.
On the other hand, the functioning of ATES can negatively affect bioremediation of VOCls, and vice versa. The possible disturbance on reductive dechlorination from external unsuitable groundwater with high redox state due to groundwater movement, and biological clogging on ATES wells due to biomass growth from bio-stimulation approaches are so far the most concerns for the application of ATES on contaminated fields. As a result, combing ATES and bio-stimulation as an enhanced bioremediation technique or system requires both comprehensive study of the biogeochemical aspects on different processes as well as characterization of subsurface conditions, and later optimization of engineered system design.
This PhD project aims to investigate the feasibility of combining ATES and bioremediation of VOCls, and study the mutual effects between them. This lecture will provide an overview of the whole PhD project, including latest results, conclusions and future perspective, from not only lab experiments (both batches and columns), but also from numerical models.
Chlorinated Volatile Organic Compounds (CVOCs) are often remediated by means of Enhanced Reductive Dechlorination (ERD). While the working principle and the design criteria are well known in the remediation sector, construction and operation details, which could seem trivial in the design phase, may lead to a significant increase in the Operation and Maintenance (O&M) costs if not properly addressed. Moreover, an adaptive approach, oriented to the optimization in every project phase can contribute to achieve the remediation goals in the planned timeframes. An ERD project led by ARCADIS in an urban area in Germany is used as an example to show how the combination of the adaptive approach with the optimization of technical details could lead to a successful remediation even with a limited accessibility of the contaminated area that is densely covered with buildings.
The contamination at the site was caused by unknown volumes of CVOCs, released by a metalworking factory. The CVOCs are present both in the shallow, low conductive porous aquifer and, in lower concentrations, in a second deeper aquifer in the fractured bedrock. The site was first remediated starting at the end of the 1980s using a combination of Pump and Treat in the aquifer and SVE in the vadose zone. These remediation measures were unsuccessful; ARCADIS was therefore commissioned with a new remediation plan. After integrative investigations and the definition of the groundwater model, ERD was chosen as most feasible remediation method. According to the new remediation plan, diluted molasses would have to be used as organic substrate to promote the biological degradation of the CVOCs. At the beginning of the remediation, concentrations of CVOCs up to 20 mg/L were present in the porous aquifer, and 3 contaminated hot spots were known.
From the very start of the ERD-remediation the injection and monitoring have been managed in a flexible way to address the critical contaminated hot spots. Between the regular monitoring campaigns on all available groundwater wells, more frequent samplings of critical wells were performed and through their evaluation the next injection round was adaptively planned. Through this approach an optimal molasses concentration and optimal injection parameters were selected and further used.
After approximately two years of active remediation only one critical contaminated hot spot was left, which is for the most part covered by a building. After having tried to address this hot spot by increasing the injection volumes in the injection points upstream (to increase the radius of influence and get to deliver the substrate to the soil volume underneath the building), a new injection well in the proximity of the building was installed. The well construction was used as a chance to gain more information about the source area: soil samples were taken and hydrophobic dye soil-water shake tests were carried out to assess the possible presence of residual DNAPL. Through the information collected it was possible to better localize the main contamination source, on which the last remediation efforts were concentrated.
Meanwhile the daily operation of the injection plant proved the efficacy of some design choices. For example, diluting the molasses on site by pumping it through a static mixer in the drinking water stream, biofouling was substantially reduced in comparison to plants in which the mixing happens beforehand, the maintenance was reduced and the molasses could be preserved undiluted for months. Other aspects were optimized during the remediation. For instance, instead of continuously injecting for a long time, the remediation plant was activated intermittently to reduce the pressure within the pipes. Appropriate remediation steering avoided any problems concerning outgassing in the urban remediation area.
The combination of the adaptive approach with the technical optimization allowed reducing the contaminant mass flux to values below the regulatory limit. The remediation was therefore ended, exactly as planned, after four years. Currently the site is monitored to check whether rebound occurs and that the expected transition to the natural attenuation of the residual contamination takes place as postulated.
Bioremediation of chlorinated ethenes and many other chlorinated compounds is optimal at neutral pH with pH’s below 6.0 considered problematic for bioremediation. For example, complete biodegradation of chloroethenes to ethene, is often inhibited below pH 6.0. Given that both reductive dechlorination and fermentation of commonly used electron donors are acid generating processes, enhanced bioremediation has the potential to decrease pH into the inhibitory range, even if prior to biostimulation, pH was acceptable.
In recent years, modifying aquifer pH using buffering agents such as sodium bicarbonate and various commercial formulations has become increasingly common. Aquifer pH modification has met with varying
degrees of success depending on application method, site geology and geochemistry but is generally considered challenging. Effective alternatives or complimentary approaches would be welcome and could improve bioremediation outcomes.
In certain cases, especially where pH is near or slightly below 6.0, the use of bioaugmentation cultures acclimated to lower pH has the potential to reduce the need for aquifer neutralization. Increasing evidence indicates that complete dechlorination to ethene is possible below pH 6.0 with pH tolerant bioaugmentation cultures. Also, previous studies have indicated that certain electron donors have a reduced acidification impact, particularly formate (McCarty et al., 2007) which generates neutralizing bicarbonate alkalinity upon fermentation. The use of electron donors with reduced pH impact, combined with pH tolerant bioaugmentation cultures has the potential to achieve successful bioremediation results with reduced need for aquifer pH adjustment.
The development and field use of low pH acclimated cultures will be discussed and case studies presented. At a Site in Florida, with the pH ranging between 5.5 and 6.0, PCE, TCE and cDCE were completely dechlorinated to VC and ethene within 6 months of bioaugmentation with a low pH tolerant bioaugmentation culture.
Trichloroethene (TCE) is a priority pollutant and among the most frequently detected contaminants in groundwater. The currently available bioremediation measures have certain drawbacks like e.g. the need for auxiliary substrates. Oxidation of chloroethenes under aerobic conditions represents a promising way to deal with the shortcomings of anaerobic reductive dechlorination.
Aerobic oxidation is possible via metabolic degradation with the pollutant serving as growth substrate as well as via cometabolic degradation depending on the presence of a suitable auxiliary substrate. Metabolic pollutant degradation is superior for field applications compared to cometabolic degradation since it does not require the presence of oxidisable auxiliary substrates within the plume. Furthermore, additional oxygen consumption by the auxiliary substrates is avoided. Thus, aerobic metabolic degradation can occur even in aquifers with low organic carbon content, in which cometabolic aerobic degradation as well as anaerobic reductive dechlorination will be hampered due to limited availability of auxiliary substrates.
In our study, the aerobic biodegradation of TCE as the sole growth substrate was demonstrated. This new process of metabolic TCE degradation was first detected in laboratory groundwater microcosms. Further experiments with the enriched mixed bacterial culture in mineral salts medium showed sustained long-term TCE biodegradation down to concentrations below the detection limit. Aerobic TCE degradation resulted in stoichiometric chloride formation and bacterial growth (increase of DNA). Stable carbon isotope fractionation was observed providing a reliable analytical tool to assess this new biodegradation process at field sites. Please refer to Schmidt K. R., Gaza S., Voropaev A., Ertl S., Tiehm A. (2014) Aerobic biodegradation of trichloroethene without auxiliary substrates. Water Res. 59: 112-118 for further information.
Further studies are currently conducted to prove field applicability of the aerobic metabolic TCE biodegradation by a field test with in-situ delivery of oxygen into a joint aquifer.
Aerobic metabolic TCE degradation might represent a new and promising concept for monitored natural attenuation (MNA) approaches or engineered bioremediation of contaminated sites (enhanced natural attenuation, ENA). Those remediation approaches should have advantages compared to reductive dechlorination or cometabolic degradation and can be considered cost-efficient and environmental safe.
Based on these results the assessment of aerobic metabolic TCE degradation at field sites is highly recommended. The observed stable carbon isotope fractionation provides a reliable analytical tool to monitor and quantify aerobic oxidative degradation pathways in the field.
Financial support provided by the German Federal Ministry of Economics and Technology (grant number: 16224 N) is acknowledged. The authors thank Michael Deusch, Siegmund Ertl, Markus Friedrich, Holger Hansel, Michael Heidinger, and Andrey Voropaev for their support.
In situ bioremediation of chlorinated solvents faces particular challenges at operational facilities posed by practicability issues, most notably accessibility. This paper will examine two case studies where remedial strategies employed complementary approaches or treatment trains to address historic losses of tetrachloroethene (PCE) and trichloroethene (TCE) at operational sites in the UK.
At the first site, TCE concentrations averaging 2900µg/l showed little evidence of degradation, with degradation products being less than an order of magnitude (cis -1,2-dichloroethene (cis-DCE) being <0.01mg/l in source zone and vinyl chloride (VC) below detection) . Groundwater conditions were mostly aerobic, so conditions were unsuitable for reductive dechlorination and elevated concentrations of competing electron acceptors were also present such as sulphate. The remedial strategy consisted of injection of a lactate-based hydrogen release compound (HRC®, manufactured by Regenesis) accompanied by HRC primer to acclimatise the groundwater for reductive dechlorination, which was duly demonstrated by successive increases , followed by decreases in the degradation products cis-DCE, VC and ethene. An order of magnitude reduction in total chlorinated ethenes was achieved in two years, and despite the initial absence of any significant reductive dechlorination, no inoculation with Dehalococcoides was necessary. A soil vapour extraction scheme, undertaken in parallel with the groundwater successfully reduced vadose zone concentrations of TCE in soil above the impacted area, the aeration having no effect on redox conditions and no inhibitory effects on reductive dechlorination proceeding within the underlying groundwater.
The second site by contrast had been subject to a much greater degree of impact (and by PCE as well as TCE), including the presence of localised DNAPL in a more cohesive geological formation consisting of a gravelly clay. Reductive dechlorination was already well advanced but access to a significant area of the source of the contamination was restricted, so the overall aim was to mitigate the potential for any off-site migration as a first priority whilst achieving a reasonable degree of mass removal within the source and plume subject to the constraints of on-site operations.
A three-fold strategy was therefore implemented involving (i) periodic injection of HRC as a ‘barrier’ hydraulically down gradient at the site boundary to protect off-site receptors, (ii) application of a percarbonate-based chemical oxidation reagent, Regenox followed by HRC in the source area and (iii) HRC alone in the plume, the HRC applications comprising both a primer and an extended release formulation HRC-X. The purpose of the Regenox was to achieve some immediate mass reduction and/or conversion to more labile intermediates but also to enhance the availability of the contaminant for subsequent degradation. Application of both Regenox (involving three successive rounds of injection over three months) and HRC resulted in a significant mobilisation of PCE or TCE from sorbed or localised DNAPL into the aqueous phase, which subsequently underwent rapid conversion to cis -1,2-dichloroethene followed by a slower reduction to vinyl chloride and then through to ethene.
Notwithstanding some continuing dissolution into the aqueous phase within the source area and immediately down hydraulic gradient from it, degradation has been proceeding at a steady rate in localities towards the boundary. Here, following initial mobilisation, total chlorinated hydrocarbons in groundwater rose from tens of thousands to over 100,000µg/l before being reduced by two-orders of magnitude to concentrations of less than 1,000µg/l, five years after treatment commenced.
The paper will discuss the variation in CHC behaviour in response to active remedial intervention according to its nature, severity and distribution and how remedial progression can be assed using the’ chloride index’, in conjunction with mass removal.
Background / objective
At a former tar production plant of ca. 6,8 ha, high concentrations of organic contaminants are present in the quaternary layer. Tar DNAPL is present at a depth of ca. 15 m-below ground level (bgl), on top of the Tertiary layers underneath important parts of the site. The contamination has migrated under the adjacent River Scheldt underneath an ecological valuable area. The DNAPL-contamination threatens the underlying Tertiary aquifer (important source of drinking water extraction) and downstream areas. The design of a remediation strategy was challenging, due to the size and depth of the contaminated area, the complex alluvial (hydro)geology, the presence of an active chemical production site and the presence of many stakeholders.
Approach / Activities
Initial feasibility studies showed that complete cleanup of the site was not cost effective. Hence, the remediation strategy design focused on elimination of the migration risk. To be able to identify the crucial aspects of the migration risk an elaborate Conceptual Site Model has been developed. In addition to conventional drillings and monitoring wells, next generation techniques have been used to map geology and contamination in three dimensions: LIF-CPT (ROST), electrical CPT and geoelectrical tomography. These data provided the means to identify gaps in the underlying Tertiary clay layer, to map the migration of DNAPL underneath the River Scheldt, to delineate in detail the presence of contamination in the different soil layers and to set up a hydrogeological model.
Results/outcomes
Based on these insights, a robust containment strategy was designed and approved by the authorities. Isolation of the contamination is to be attained by a three-sided bentonite slurry wall, to be installed in 2016/2017, combined with limited pumping of groundwater to compensate for ground- and rainwater inflow. Forty DNAPL-recovery wells are installed in some selected critical locations and at present manual pumping of DNAPL using a peristaltic pump is undertaken. A detailed testing phase provided the ideal pumping rates and tube diameters for the selective removal of DNAPL. Results showed that it was crucial to develop a different pumping schedule for every well, because of heterogeneity of the DNAPL inflow rate. First results of the full scale system are promising: a total removal rate of more than 1.000 liter DNAPL/day was attained. A further elaboration of the technique, as well as automation of the system is expected to increase the removal rate in the near future. More results will be available at the AquaConSoil conference.
Numerical contaminants’ fate and transport (F&T) modelling has been commonly used: (i) to describe and predict contaminants’ distribution and migration in groundwater, (ii) to improve understanding of processes occurring in the subsurface and influencing the contaminants’ migration; (iii) as a framework for data integration and interpretation; (iv) to assess risk associated with groundwater contamination, (v) to predict contaminants’ behavior under different scenarios, and (vi) to improve groundwater monitoring network. In this work we applied F&T modeling for selecting effective remediation of contaminated groundwater.
Selection of the most effective remediation scenario for contaminated groundwater is a complex issue that requires a suitable methodology. An important part of it is F&T modeling, preceded by field and laboratory investigations. The simulations enable to forecast contaminants’ migration in the aquifer depending on different remediation scenarios and present the results in a friendly way by visualization of concentration changes in time and space. However, the model’s credibility depends strongly on series of conditions including: proper site investigations, relevant conceptual site models, appropriate estimates for model parameters and selecting the most suitable algorithms to fit the conceptual models. The obtained results should be always treated as an approximation what is associated with the nature of the modeling tool: developing the conceptual scheme requires simplification of real-world conditions due to capability of computer programs. An insufficient access to the aquifer is another important issue that may strongly affect the modelling results. The modeling approach should include detailed calibration to match the simulated and observed parameters, and validation – the process of evaluating and testing the different aspects of the model in order to refine and enhance the model.
A site with TCE and PCE contaminated groundwater located in south-east Poland was selected as a case study to present an application of F&T numerical modeling for selecting an effective remediation strategy. A methodology was developed, that included: field and laboratory investigation followed by numerical groundwater flow modeling and contaminants’ F&T modeling. The selection of effective scenarios was based on a multi-criteria analysis (MCA), and a monitoring network was designed to control the performance of selected remediation scenario.
The contaminants’ F&T model was developed using Visual MODFLOW software in MT3D environment. Based on the defined criteria simulations were conducted for a number of selected groundwater remediation strategies: (i) natural attenuation (NA) based remediation, (ii) ‘pump and treat’, (iii) permeable reactive barriers (PRB), and (iv) in situ chemical oxidation (ISCO) applied locally in the contamination source area. To perform a comprehensive evaluation simulations were conducted for a 100-year period. Changes in contaminants’ concentrations were evaluated in 1-year periods and presented graphically. Localization, configuration and other characteristics (e.g. pumping rates, PRB permeability parameters) of the remedial installations were adjusted manually by the trials and errors method.
The estimated times required to reach the defined remediation goal (i.e. TCE and PCE concentrations in water <50 µg/dm3 required for a ‘good’ chemical status of groundwater) for studied scenarios varied from 20 to more than 100 years. The most effective remediation strategy was selected based on the MCA which included: (i) the environmental criterion (i.e. reaching the ‘good’ chemical status of groundwater: ia – in immediate surroundings of waterworks, ib – in whole study area); (ii) the waterworks operational criterion (i.e. drinking water standards (ƩTCE+PCE <10 µg/dm3); (iii) the economic criterion (investment and operational costs). Each adapted criterion was weighted based on the site-specific factors as: 0.4, 0.3, 0.2, and 0.1, respectively. The results indicated that ‘pump-and-treat’ was the most effective method of groundwater remediation under the assumed conditions, followed by PRB and ISCO. NA turned to be the least suitable requiring the longest time to obtain the remediation goal, particularly due to small sorption and unfavorable hydrogeochemical conditions for intrinsic biodegradation.
Concluding, numerical contaminants’ F&T modeling allows simulating different remediation strategies, thus it can facilitate the decision making process. The developed methodology for assessing effective remediation methods based on F&T modelling and the MCA may be applied also at other sites contaminated with other contaminants. However, the selection criteria should be set for each site individually. The prescribed weights in MCA allow to point out the most important factors to deal with from an investor’s viewpoint, as well as from administrative, formal, environmental, social, etc. perspectives.
Introduction.
In situ chemical reduction (ISCR) is a technique commonly used to transform highly toxic and soluble hexavalent chromium (CrVI) into relatively low toxic and less mobile trivalent chromium (CrIII). There have been several studies focussed on CrVI contaminated groundwater, but in situ remediation techniques of unsaturated soils have not been thoroughly tested. The Spinetta Marengo (SM) industrial site (Alessandria, Italy) was contaminated with cromium (Cr) as a result of the activities of the chrome planting facility that was dismantled in the mid-1970s. Data indicated that the source of groundwater contamination was CrVI in the unsaturated soils. A novel pilot test study was conducted at the SM site to evaluate how effective different treatment techniques were in reducing CrVI concentrations in the unsaturated zone.
Material and Methods.
Core samples were submitted for preliminary laboratory treatability studies (batch and column tests). Results indicated that sodium dithionite was the most appropriate reagent for treating the subsurface contamination.
Field scale pilot tests were conducted that involved injections of sodium dithionite in an area historically used for dichromate ore processing where some of the highest solid phase CrVI concentrations had been observed in the unsaturated zone.
Pre-treatment sampling. Soil samples were collected to the maximum depth of 6m bgl and analysed for solid phase total concentrations of Cr, CrVI, Fe, S, Mn, As, Ni and Fraction Organic Carbon (fOC). The CrVI concentrations ranged from 78 to 3000 mg/kg. The monitoring network implemented for the pilot test consisted of three fully screened piezometers and six boreholes for georadar investigation. Pre-treatment CrVI concentrations in groundwater ranged from 0.45 to 3.2 mg/L.
A stoichiometric excess of sodium dithionite was added to an aqueous solution with a sodium carbonate pH buffer.The solution was formulated and immediately injected to prevent dithionite reaction with O2. The solution presented a negative redox potential (-600 mV vs NHE), a significant electrical conductivity, and alkaline pH (10-12). Three injection tests were conducted from June to October 2012.
Injection Test I consisted of a grid with four direct push injections, spaced 1.8 m from one another. At each point, 1000 L of solution were delivered between 2.0-4.0 m bgl, at a flow rate of 70 L/min. The direct push rod was fitted with a four-port Geoprobe® injection tip to facilitate reductant delivery at specified depths.
Injection Test II included two injection wells installed 1.8 m from one another. The two wells consisted of two inch diameter PVC screened from 2.0-4.0 m bgl. At each point, 1000 L of solution was injected at an average rate of 125 L/min.
Injection Test III included a single multi-step direct push injection. During injection, a 500 L solution was delivered between 0.5-1.0 m bgl, to force the reductant into the filling material and fine-grained silt unit, and an additional 2000 L solution was delivered between 2-4 m bgl.
Geophysical monitoring. High resolution electrical resistivity tomography, surface and borehole georadar techniques were performed before, during and after the injections, and a time-lapse geophysical approach was adopted.
Groundwater monitoring. Based on numerical modelling simulations, a groundwater monitoring campaign was carried out to determine baseline hydrochemistry and hydraulic heads and continued during and after the injections with defined intervals, approximately ranging from 24 hours to a week. All the groundwater samples were analysed on site for CrVI, electrical conductivity, temperature and pH. Additional groundwater samples were collected and analysed for total concentrations of Cr, CrVI, Mn, As, Ni, Fe, SO42-.
Post-treatment soil sampling. Based on geophysical evidences, post-treatment soil samples were collected in the highly perturbed areas (resistivity anomalies lesser than -30%) to evaluate the effectiveness of the treatment.
In situ water flushing. An injection of 1500 L of water into the treatment zone was accomplished with Geoprobe® technology in November 2012. Groundwater samples were collected and analysed before, during and after injection to verify the mobility of CrVI in the unsaturated soils.
Results
The injection caused a significant reduction of resistivity in the unsaturated soils, ranging between -10% and -70%. The data indicated an average radius of influence of 1.1 m for each single direct push injection, with a maximum of 1.5 m, and a treated unsaturated soil volume ranging from 6-9 m3. Post-treatment soil samples collected in the treatment zone indicated a significant decrease in CrVI concentrations: less than the detection limit of 1 mg/kg. As expected, the excess of dithionite rapidly turned to sulphate and insoluble metal sulfides were formed. The total sulfur concentrations in the unsaturated soils increased to 3490 mg/kg following the reductant injection. The average total Cr concentrations in the core samples collected before and after treatment showed no significant changes.
Conclusions.
The investigations proved the capacity of geophysical monitoring to clearly evidence the reductant migration in the unsaturated zone. Concentrations of CrVl in the unsaturated soils were reduced by approximately 80-100% after injecting sodium dithionite with a four-port Geoprobe® tip. Finally, pilot testing indicated that direct push injections of sodium dithionite at specified depths is a viable treatment technology for unsaturated soil remediation at the SM site.
Acknowledgments. The authors would like to thank Solvay Specialty Polymers for funding this project.
Background/Objectives: A combination of laboratory experiments, field hydraulic and transport tracer studies, and numerical modeling were used to design a Surfactant Enhanced Aquifer Remediation (SEAR) of a sandy aquifer contaminated by petroleum based jet fuel (LNAPL) at a Danish Defense tank storage facility situated in western Jutland in Denmark. In the full scale application, a blend of anionic surfactant in a brine solution (sodium chloride) will be injected into the subsurface to mobilize free-phase and residual NAPL from subsurface soils to downstream extraction wells. The SEAR will utilize foam in the aquifer to improve mobility control and to enhance remediation in the smear zone. The use of surfactant and foam is a well-established technology for enhanced oil recovery in the oil industry. The technology has also been proven in remediation of both LNAPL and DNAPL in both the laboratory and in the field. The use of numerical models, calibrated to both laboratory and field studies, at every stage of the design process has provided essential information for the design of the final SEAR, currently scheduled for spring 2015.
Approaches/Methods: During planning and design of the SEAR, numerical models have been tools for understanding phase behavior, decisions on use of technologies, and in the SEAR design. As a first step, the multi-phase model UTCHEM was calibrated to laboratory partitioning experiments to ensure that phase behavior could be accurately simulated over the range of expected field conditions. UTCHEM phase behavior and other physical/chemical parameters were further refined by matching simulated breakthrough curves of aqueous, oil, and microemulsion phases to breakthrough curves measured in laboratory column studies of surfactant flooding. Very close matches between measured and simulated phase behavior and breakthrough curves were obtained.
The field-scale SEAR design was completed in several stages. First, the numerical models MODFLOW and MODPATH were used to design a preliminary injection/extraction well network. The MODFLOW model hydraulic conductivities, storage coefficients, and stratigraphy were adjusted until the flow patterns matched data from pumping and slug tests. A chloride tracer test was then simulated with the MODFLOW and MT3D to estimate the degree of subsurface heterogeneity, fine-tune flow and transport parameters, and ensure that injected fluids would be captured by the extraction wells.
Following the hydraulic simulations, a UTCHEM model was created that matched the characteristics of the MODFLOW model. The UTCHEM model was then run to determine optimal fluid injection rates, expected phase production at the extraction wells, injection and production well depths, foam injection rates and effects, and other operating parameters. The operating parameters and alternative well configurations were altered to maximize oil removal while ensuring recovery of injected fluids. The final UTCHEM simulations form the basis for the planned SEAR operating conditions
Applications: The combination of multi-phase simulations, field studies, and laboratory experiments is a powerful technique for designing SEAR remediation projects. SEAR projects frequently do not meet performance expectations because the complexities of the processes involved are difficult to estimate without careful study. These design techniques can be applied to many other planned SEAR projects to increase their chances for success and give regulators better data on which to base decisions.
Lessons learned: The use of numerical models has been a helpful tool in understanding the remediation processes compared to the often used “black box” approach, in which remediation selection and performance are evaluated by laboratory parameters and monitoring data from the field without a thorough understanding of the processes. The correlation between laboratory, field and model results gave understanding, knowledge and credibility in choice of surfactant blend and set up and design of the full scale remediation. The results of the simulations were also helpful to regulators, who were able to use the results to set up terms and permits for the full scale application and to accept endpoints of a full scale remediation.
In-situ chemical oxidation (ISCO) by means of Fenton reagents is an established method for treating groundwater pollution. The utilization of the Fenton cycle for the production of highly reactive OH-radicals from hydrogen peroxide needs auxiliary materials. Complexing agents and/or acids are required in order to keep the catalytically active Fe- cations in the dissolved state.
In the EU-project NanoRem a variation of the conventional Fenton-based ISCO process is developed. The disadvantages of dissolved Fe are avoided by the use of Fe-loaded zeolites as catalysts. Contrary to Fe- ions as catalyst, the formation of OH-radicals at the Fe-zeolite takes place at neutral pH without the necessity for other agents. Furthermore, the zeolite framework adds sorption properties to the system, so the reactive species are formed at the centres of the highest local concentration of the target contaminant. This system offers some target selectivity due to its sorption properties towards non-polar molecules and the size-selectivity provided by the zeolite framework.
For the intended application, colloidal suspensions of Fe-zeolites with a particle size in the lower μm-range shall be injected into the subsurface where they will be immobilised on the sediment after a certain travel distance. The zeolite particles form a permeable sorption barrier which will cut off contaminant plumes by means of adsorption. After particle loading by sorption, the barrier will be regenerated by the injection of H2O2. Therefore, the injection of catalyst and oxidant is separated in time and space, offering safety and economic benefits compared to common Fenton-based ISCO. In case of plume treatment, the combination of sorption and subsequent oxidation should provide a more efficient use of H2O2 per mass of target contaminant.
Tracking Fe-zeolite particles in sediment is a very challenging task. Methods based on element composition cannot be used, since Fe-zeolites are composed of ubiquitous elements (Fe, Si and Al). Other sum parameters like turbidity only work under well-defined conditions. and iInherent zeolite properties like their high specific surface area can be used but are not applicable in a routine analysis setup.
We will present results on the issue of Fe-zeolites monitoring in water and sediment matrices. Since fluorescence as detection principle has the potential to solve many issues in tracking particle fate in the environment, a method to irreversibly label zeolites with a fluorescent dye was developed. A fluorescent dye molecule is synthesized inside the framework of the zeolites from educts which are small enough to enter the channel system. The resulting product, on the other hand, is too big to exit the channel system. This type of process is called ship-in-a-bottle synthesis. Verification of the applicability for zeolite tracing includes experiments on detection limits in various water and sediment matrices, stability against leaching and oxidants and representativeness (i.e. exclusion of impacts of labelling on particle key properties such as mobility).
Acknowledgements: This work was supported by funding from European Union within the NanoRem project.
Organizers: EU FP7 HOMBRE, EU Snowman Balance4P,
Contactperson : Maaike Blauw (Deltares)
This session will include a short introduction presentation and discussion with the audience.
Currently an Urban Agenda is being set up by the European Commission, because Europe continues to be faced with challenges related to the economy, the climate, the environment, and society at large. Most of these challenges have a strong urban dimension. Although cities’ role for economic, social and cultural development, and their potential for a more resource efficient habitat, have long been recognized, the policy response at European and national level has been slow. For example: the resource efficiency gains made possible by compact urban settlements are being undermined by uncontrolled urban sprawl that puts public services under pressure and reduces territorial cohesion (COM 2014 490).
Brownfield sites are the secret weapon in delivering sustainable European cities. Although these sites often have contamination problems and require intervention to bring them back into beneficial use, they are also often in the right place to deliver profitable places for people. Within the FP7 project HOMBRE the Zero Brownfield Framework is developed, where the main goal is to avoid unnecessary emergence and undue persistence of brownfields, by decoupling the land use and land management cycles. When a land use ceases to be beneficial to society, land management should facilitate the transition towards another sustainable use.
Outline:
- Presentation: Zero Brownfield Perspective: explain framework, how it works and remaining questions (15min)
- Presentation: EU Urban Agenda (15min) (we are
- Discussion: Towards Urban Land Management 2065: what research and development is needed to enable that cities contribute positively to a resource efficient Europe. (45 min)
- Conclusions and further actions (15 min)
For this session persons from CEMR (Council of European Municipalities and Regions), URBACT, DG Region and Common Forum, and from other Member States involved in urban land management will be invited to contribute to the session and stimulate the discussion. The session will have an EU focus, therefore people from different Member States will be involved in the session.
Municipality of Utrecht is setting up an Interreg Proposal concerning Urban Land Management. This project can also be used in the session to support the Urban Aganda and Urban Land Management.
Presenters and moderator:
At the moment we are approaching someone from DG Region (connected to Urban Agenda) to present the Urban Agenda.
The introduction of pollutants in to the environment around us is a constant threat. Often the concentrations of such pollutants are very low and their detection is challenging. Passive samplers provide a simple and robust monitoring tool used in order to monitor the transport and fate of organic and inorganic pollutants in the water phase. The principle of passive sampling is based on the free flow of pollutant molecules from the sampled medium to a sampling device as a result of a difference in pollutant chemical potential in the two media.
Environmental compliance with existing and new legislation is necessary in order to maintain and improve the quality of the environment. With an ever increasing number of pollutants requiring monitoring, and more stringent environmental quality standards being put in to place, there is a need for a low cost yet reliable method for measuring contaminants at trace levels.
Passive samplers have a very important role to play in the monitoring of the fate and transport of pollutants in the real world. Some key applications will be illustrated through the use of real field examples that are grouped according to:
• Pollutant source identification
• Tracking the fate and transport of pollutants in water (ground, surface and fjord), sediment and air
• Pollutant monitoring in combination with complimentary methods
• Risk assessment
The examples that will be discussed in which passive samplers have been used to monitor diverse pollutants include:
• Within the research project WASTEFFECT funded by the Norwegian research council a robust waste emission and exposure model for waste regulators and companies to anticipate and reduce risks from emerging contaminants is being developed. Passive sampling strategies have been developed in order to determine the concentration of brominated flame retardants (BFRs), bisphenol A (BPA) the endocrine disrupting compound, and antimony (Sb), a toxic metalloid in various waste streams. Diffusive Gradients in Thin-films (DGT) devices have been used in order to measure the freely dissolved concentration of Sb. BFRs and BPA have been measured in the water phase and in the air phase with the use of several different types of passive sampler membrane materials. Freely dissolved concentrations of BFRs and BPA have been determined with the use of polydimethylsiloxane and polyoxymethylene (POM) respectively, and air concentrations of contaminants have been sampled with the use of XAD beads, a type of polystyrene copolymer resin.
• The Impact of Climate Change on the Quality of Urban and Coastal Waters - Diffuse Pollution (diPol) project aimed to identify impacts and suggest measures to reduce adverse consequences of climatic changes impacting the quality of urban and coastal waters. The concentrations of PAHs and PCBs in the inner Oslo fjord were measured using total water sampling (taking a grab water sample and extracting it with solvent) and with polyoxymethlene passive samplers. By following concentrations over time, temporal and spatial patterns could be identified.
• A landfill used between 1953 and 1965 for industrial waste from a Hydro power plant containing PAHs, heavy metals, oil and tar provided a field case study for the comparison of passive sampling methods and total water sampling. Passive samplers made of polyoxymethylene to sample organic compounds and DGT devices to sample metals were placed upstream, just outside and downstream the landfill in order to track changes in concentration spatially. All of the passive samplers displayed similar concentrations showing no evidence of increasing concentrations just outside the landfill compared to upstream the site. Although the total water concentrations were higher than the freely dissolved concentrations, the passive sampler results allowed the conclusion to be drawn that pollutants were not being released from the landfill in its current state
In addition a focus on the use of passive samplers in risk assessment will be discussed. Passive samplers can be used in order to determine how strongly pollutants are bound to contaminated soil or sediment, which is a pivotal piece of information when the risk such pollutants pose via leaching and spreading to the surrounding environment needs to be considered. By carrying out a simple laboratory experiment in which passive samplers are exposed to the contaminated soil or sediment, the soil or sediment – water partitioning coefficient value (Kd) can be determined. Indeed, in the model developed by Miljødirektoratet to assess contaminant spreading and the negative effect it could have on the environment, the use of site specific input model parameters are encouraged. In this context, the determination of the soil or sediment-water partitioning coefficient for a particular pollutant can be used and reduce the inherent conservatism in the model. Several examples will be given to highlight the vital nature of the information obtained via the use of passive sampling.
Nowadays with technological advances, the use of environmental forensic approaches could help to characterize the various sources of groundwater contamination. This implies the need of specific analytical methodology to identify micropollutants, emerging substances or transformation products present at low concentrations. The high resolution mass spectrometry (HRMS) has gained increasingly in importance for monitoring organic compounds. Its high resolving power, mass accuracy and the sensitive full spectrum acquisition are the key points. Contamination profile and pattern of a specific site could be highlighted by this technique with the use of automatic data processing softwares.
The aim is to support public policy development by highlighting and identifying relevant compounds to be monitored in groundwater. The main difficulties for the implementation of monitoring are sometimes low and fluctuating concentration levels and complex mixture of pollutants. No therefore there is a strong interest to combine passive sampling to HRMS. Passive samplers allow accumulating compounds during exposure that improve trace detection and integrating pollution fluctuations. The Polar Organic Chemical Integrative Sampler (POCIS) was employed to sampling polar and semi-polar compounds (pesticides, pharmaceuticals, phenolic compounds, triazoles….).
Different sites impacted by agricultural, urban or industrial pollution sources were investigated and sampled during several months. Grab and passive sampling were deployed and analyzed by LC-QTof. To process data, different approaches were investigated. The first one is based on research from compounds listed on our homemade database (around 450 with experimental data on our system as retention time, exact masses for molecular and fragment ions). The non-targeted screening was applied using statistical tools such as principal components analysis (PCA) with direct connections between original chromatograms and ion intensity. Trend plots are used to highlight relevant compounds for their identification. In tandem with this work, laboratory calibration was made with POCIS in order to obtain uptake rate constants for target compounds.
This approach allows making comparison of samples and giving multidimensional visualization of chemical patterns such as molecular fingerprints and recurrent or specific peaks of each site. The identification of relevant signal is partially succeeded by using different databases such as Norman Mass Bank or Chemspider. The workflow used allows identifying sentinel molecules and molecular clusters as compounds never revealed in these sampling sites. From data acquired by the results post-processing, it has been possible to quantify targeted compounds by using acquired data on POCIS laboratory calibration.
Background
Today measurements of volatile organic contaminants (VOC) in indoor air, e.g. trichloroethylene (TCE) and tetrachloroethylen (PCE), are performed with passive samplers (sorption tubes) over a period of typically 14-21 days. After this period the samples are returned to a laboratory for analysis. The result obtained corresponds to an average concentration over the entire sampling period. As an alternative, short time active sampling using sorbent tubes containing activated carbon can be performed.
Previous studies on vapor intrusion have shown large variations spatial and over time in VOC concentrations in both soil air and indoor air at contaminated sites. At present no simple, effective and inexpensive method for direct quantitative measurements of VOC in air exists.
After more than 5 years of intensive research DTU Fotonik have developed a revolutionary mid-infrared detector based on upconversion of the signal which reduces the noise level by a factor of millions compared to alternative detectors. The measurements are performed by sending an infrared laser beam through a specified air volume. The bonds in VOCs will absorb specific wavelength of the light and by detecting changes in the light using the patented upconversion technology developed by DTU Fotonik it is possible to quantify very low concentrations of PCE, TCE and other VOCs in the air.
The purpose of this project is to build and test a system based on the optical sensor to measure PCE and TCE in soil air and indoor air related investigations of contaminated sites.
Approach and Results
The project consists of two phases; 1) design and construction of a compact laboratory setup and 2) field test with the equipment. At present the setup has been build and the final calibration of the system is being performed in the laboratory before field tests are initiated.
The setup consists of a tunable Quantum cascaded laser system (QCL) in the 9 to 12 µm range, a Herriot multipass cell (36 m path length), combined with an upconversion system for low noise conversion of the long wave infrared signal to the near infrared region for detection using standard Si-based detectors. The long interaction distance in the multipass cell ensures proportionally higher sensitivity to PCE/TCE. The combination of the QCL and upconversion system, provides a stable low-noise signal, able to measure small absorptions of infrared light, corresponding to low concentrations of PCE/TCE.
The system is designed for the detection of VOCs like TCE and PCE in the range of 1-100 μg/m3 and with the expected upconversion efficiency, it is believed that μg/m3 sensitivity will be reached.
After the validation under controlled conditions in the laboratory, the system will be tested in field tests where short time measurements will be compared to samples actively collected on sorbent tubes. Also, continuous measurements over time will be compared to collected passive samples.
The investigated method is based on a new technology for real time measurements of VOCs in air and besides TCE and PCE, the system can be reconfigured to measure other VOCs. It is expected that the method will improve investigations of indoor air quality, help identifying intrusion pathways for VOCs to buildings, and help in several other application where fast quantitative measurements of VOCs are needed.
The project will be completed in February 2015 and all results will be presented at the conference.
The measurement and interpretation of parameter mass fluxes and discharges is gaining more and more importance. Especially in the frame of soil and groundwater contamination, remediation and related environmental risks, water management and ecosystem management, the interpretation of mass fluxes is essential. Current legislation already includes a mass flux approach today (e.g. EU Water Framework Directive and Groundwater Daughter Directive).
Environmental management actions regarding groundwater pollutions and ecosystem research and management are mostly driven by parameter concentrations. Since concentration estimates are highly uncertain and do not include the fluctuations caused by spatially and temporally varying conditions, decisions about these actions can be improved by also considering parameter mass fluxes (mass of parameter passing per unit time per unit area, or flow rate of these parameters per unit area) and parameter mass discharges (sum of all mass flux measures across an entire plume). The mass that effectively reaches a downgradient receptor, determines the actual situation and risks, and should therefore be monitored. It is essential to determine mass fluxes directly instead of estimating mass flux based on concentration data and estimates of groundwater velocity.
The direct determination of contaminant mass fluxes in soil and groundwater systems is possible with the Passive Flux Meter (PFM) technology. The PFM is a recently developed passive sampling device that provides simultaneous in situ point measurements of a time-averaged contaminant mass flux and water flux. The device, with a suite of tracers, is placed in a monitoring well or borehole for a known exposure period, where it intercepts the groundwater flow and captures contaminants from it. The measurements of the contaminants and the remaining resident tracer can then be used to estimate groundwater and contaminant fluxes.
Today, an increasing demand from different sectors for the combined determination of multiple parameter mass fluxes has stimulated us to optimize the technology and develop an integrated flux measurement device which targets the combined mass flux determination of multiple parameter types.
The principles of integrated passive flux measurements in groundwater will be presented, together with some results from field applications and their outlook within flux-based environmental management.
Two common trends have emerged from many vapor intrusion site assessments that complicate evaluation of this exposure pathway: (1) a high degree of temporal and spatial data variability and (2) uncertainty in distinguishing vapor intrusion from sources present in occupied space. These can undermine confidence among regulatory officials and potentially-affected parties that evaluations are sufficient. To minimize variability associated with complex site conditions, a Conceptual Site Model (CSM) that represents the physical and chemical processes affecting volatile organic compound (VOC) transport and distribution should guide both site assessment and the understanding of data sufficiency to outline key site processes.
To minimize variability associated with sampling bias, systematic protocols designed to verify sample quality in the field should be used. There are a range of field methods for sample collection in use, and a variety of possible biases that add to apparent variability. When data quality is carefully controlled, VOC behavior is relatively predictable, and the assessment process can be resolved with much less variability and uncertainty.
Despite increasing reliance on whole-gas sampling using passivated stainless steel canisters, a diverse suite of tools is now available to vapor intrusion investigators to manage key variables including: temporal and spatial variability; short assessment timelines; and areas of buildings that are difficult to access. Authors will review innovative techniques targeting these needs including passive quantitative sampling, high-volume sampling for sub-slab soil gas, low-conductivity soil sampling, and building pressure cycling.
A case study will be presented where mathematical modeling was used to support building pressure cycling to evaluate background sources of target compounds and subsurface sources of the same compounds in a period of hours rather than seasons of periodic sampling.
This is a proposal for a session on how the EU Water Framework Directive is handled in Europe with focus on contaminated sites threatening surface waters. In addition to the following abstract, we suggest two proposals more for oral presentation at the session.
• Experience with the Water Framework Directive and contaminated sites in the Netherlands by Eric Verbruggen (RIVM, Netherlands)
• Challenges and experience for the Danish authorities in screening and identifying contaminated sites threatening surface waters in Denmark by a representative from the Danish regions.
If this proposal for a session has your interests, we will submit abstracts on the two proposals. If you do not find space in the program for this session, we hope that the following abstract may be admitted as a lecture.
Abstract: Identification of contaminated sites threatening surface waters
Background
The implementation of the EU Water Framework Directive requires an integrating and holistic approach to legislation for water bodies with a goal of obtaining good environmental status for all receiving waters. While the risk from contaminated sites to groundwater has received a great deal of attention in the past, the risk from contaminated sites to surface waters (streams, lakes and coastal waters) has not yet been well examined. In Denmark alone there are more than 30,000 contaminated sites are registered – many of them located close to surface waters. However, the hypothesis is that only a minor part of these actually pose a real risk towards surface waters. Thus a robust method is needed to identify the few relevant sites which still comply with the precautionary principle.
Activities
Together with leading experts from universities, consulting companies and regional authorities (who are responsible for handling contaminated sites in Denmark) the Danish EPA developed a screening tool to identify contaminated sites that threaten surface waters. The screening system integrates national data of the contaminated sites: location, distance to surface waters, contamination activity, contaminant area and mass flux and calculates the mixing in surface waters. The environmental effect in surface waters was done by comparing the calculated concentrations with maximum allowed concentrations within designated mixing zones. Since the data availability and quality differs for the contaminated sites and surface waters, the screening is based on conservative default values that can be obtained from existing databases followed by a site specific assessment in order to improve the screening evaluation.
A sensitivity analysis on the input parameters for the screening tool is currently being done, aiming at focusing the effort used in obtaining the most important input parameters. Also, a description of site specific assessment activities has been done, including archive search, site inspection and simple field investigations.
Results
Assessment of the more than 1500 different possible contaminants revealed that 150 were relevant with respect to risk to surface waters. The 150 contaminants were divided in 16 classes each represented by a “worst case” model compound. Of the 30,000 registered contaminated sites, 15,000 are registered due to known activities that may involve handling of critical contaminants, but no field investigations have been carried out to confirm the presence of contaminants. Thus all activities were allocated model compounds. The maximum travel length of a contaminant plume for the model compounds were determined based on literature review and expert interviews so compound specific distance criteria could be determined. Also, conservative estimates of contaminant mass fluxes for activities and model compounds were made. Mixing in streams were calculated using analytical models that were developed (a simple and a more advanced) and mixing in lakes, fjords and along the coastline was calculated by specific numerical modeling using MIKE models. All input data are controlled by databases and GIS and implemented in a webtool.
The screening process has resulted in approximately 2500 sites that are divided between the 5 Danish regions for individual assessment which is expected to result in a list of 200-500 sites where further investigations/remedial actions are required. The most frequently found contaminants are chlorinated solvents and the most frequently affected surface water type is streams.
The sensitivity analysis has revealed that good knowledge of the geographical, geological and hydrogeological conditions are important – for instance the flow direction and the likelihood of hydraulic contact between groundwater and surface water. In addition, the type of contaminants and type of point source is crucial information to ensure a reliable risk assessment. Finally, simple inspection of the surface water contribute to the subsequent risk assessment.
This study is accomplished within the framework of SILPHES financed by ADEME, the French Environment and Energy Management Agency (AMI 2013 program). SILPHES is a "technology demonstrator" project which aims at developing innovative solutions for in situ remediation of a mixture of recalcitrant chlorinated solvent, mainly composed of hexachlorobutadiene, hexachloroethane, PCE, TCE and hexachlorobenzene. SILPHES is organized around two fundamental and complementary tasks:
- The remediation of chlorinated solvents point source pollution. This part is devoted to the optimization of the treatment of the point source, which includes physical, chemical and thermal treatments, associated with diagnostic and monitoring;
- The remediation of chlorinated solvents plume. This part is devoted to the improvement of environmental diagnosis and the design and monitoring of natural attenuation, bioremediation or chemical treatment.
This paper only covers a part of the first point stated above, i.e. the remediation of the residual phase of chlorinated solvents remaining after pumping.
Since the 1990s, in situ chemical remediation is frequently considered because of good treatment efficiency without carrying out an excavation or without additional processing step. Among the in situ remediation techniques, those for the treatment of chlorinated solvents are highly widespread, essentially for the treatment of PCE and TCE [1-4] by using strong oxidizing or reducing agents. The particularity of this study is the diversity of the chlorinated solvents mixture encountered in situ: both aliphatic and aromatic compounds. As a result, molecules have different chemical affinities with reactants, so both oxidation and reduction have been studied.
The chemical degradation of the mixture was investigated in vials to define the relative efficiency of various reagents. Three oxidizing agents (potassium permanganate, Fenton's reagent and sodium persulphate) and four reducing agents (a suspension of nanoscale zero-valent iron, with or without surfactant, sodium dithionite and sodium sulfide) have been used.
All experiments were performed in 100 mL vials filled with 50 mL of deionized water and 1 mL of the mixture of the chlorinated compounds. Different concentrations of reactants were added to the batch system after removing dissolved oxygen. Six replicates of each experimental condition were performed, and all sealed vials were stirred at 100 rpm in a thermostatic chamber at 12°C, the average groundwater temperature. Samples were analyzed at specified times in order to monitor the evolution of the amounts of chlorinated compounds. Ion chromatography was used to determine the production of chloride ions. A percentage of dechlorination was calculated from the measured concentrations of chloride ions by considering a complete dechlorination of all chlorinated compounds contained in the mixture. Gas chromatography –injecting aqueous and headspace samples– was used to determine the amounts of initial compounds and intermediate products of their degradation.
Experimental results have shown that, in these operating conditions, reductants are more efficient than oxidants. The highest percentage is about 12.5 % after 80 days of dechlorination, and is obtained with a ratio of sodium sulfide equal to 5 times the theoretical stoichiometry. This low value can be explained by worse operating conditions, with amount of chlorinated solvents well beyond saturation. The maximum percentage obtained for both nanoscale zero-valent iron and dithionite is about 9%, but at different stoichiometry: at stoichiometry ratio for dithionite and at 0.39 the stoichiometry ratio for iron. Increasing the amount of iron should enhance the degradation of chlorinated solvents. Regarding oxidants, only KMnO4 have shown relevant results, but lower than those obtained with reductants.
Results obtained by gas chromatography have illustrated the evolution of concentrations of chlorinated solvents. Hexachloroethane and PCE seems to be preferentially dechlorinated in the mixture: the most important variations in concentrations were observed with them or intermediate products of their degradation. Complex patterns of degradation have been observed, so individual chemicals mechanism could not be explicitly illustrated, except for the reduction of hexachloroethane and PCE. The products of this pathway were mainly PCE (β-elimination) and pentachloroethane (hydrogenolysis), but no quantitation could be obtained.
Further studies are currently in progress. The next phase consists in studying the degradation of the mixture with amounts of reagents widely in excess to define the limits of treatment efficiency. Others chemicals will also be tested, in particular potassium ferrate (oxidant) and palladium-doped microscale zero-valent iron (reductant). Once the best reagent compositions are known, several studies will be done with three chlorinated solvents – hexachlorobutadiene, hexachloroethane and hexachlorobenzene – taken individually to establish the reaction kinetics and mechanism at different experimental conditions (pH, temperature, concentration…).
References:
[1] Amir A, Lee W (2011). Chemical Engineering Journal 170, 492-497.
[2] Amonette JE, Templeton J, Speed R, Zipperer J (1992). In: SSSA Meetings, Soil Science Society of America: Minneapolis, pp 1-16.
[3] Amonette JE, Szecsody JE, Schaef HT, Templeton JC, Gorby YA, Fruchter JS (1994). In: In-situ Remediation: Scientific Basis for Current and Future Technologies. Part 2, Gee GW, Wing NR (Eds). Battelle Press: Columbus, pp 851-881.
[4] Xie Y, Cwiertny DM (2010). Environmental Science and Technology 44, 8649-8655.
Chlorinated alkanes, including 1,2-dichloropropane (1,2-DCP), 1,2,3-trichloropropane (1,2,3-TCP), and 1,1,2-trichloroethane (1,1,2-TCA), have been extensively used as fumigants, intermediates in chemical syntheses or solvents. Due to their toxicity and recalcitrant nature, some of these chemicals are no longer manufactured but remain present at historically contaminated sites. Information describing the transformation of chlorinated alkanes under anaerobic conditions is scarce and it is limited to a few bacterial genera including Dehalococcoides, Desulfitobacterium, Dehalobacter, and Dehalogenimonas. These organohalide-respiring bacteria (ORB) can couple the reductive dechlorination of chlorinated alkanes to energy conservation and growth; therefore they are of greater interest for in situ bioremediation. To date, there are only four isolates belonging to the genus Dehalogenimonas, all of them isolated in the United States. Here, we show a stable sediment-free enrichment culture derived from river estuary sediments in Barcelona (Spain) that exclusively dechlorinates vicinally chlorinated alkanes via dichloroelimination. This reaction involves the simultaneous removal of two chlorines from adjacent carbon atoms with the formation of a carbon-carbon double bound. PCR with genus-specific primers revealed the presence Dehalogenimonas in our culture. To gain insights into the identities of dominant bacterial populations present in the enrichment culture, prominent DGGE bands were excised and sequenced. Compound specific stable isotope analysis (CSIA) was used to determine the carbon isotope fractionation during reductive dechlorination of polychlorinated alkanes. Our results show that dechlorination was accompanied by significant isotope fractionation that differs from those values described previously by other ORBs. Advances in the fundamental understanding of carbon isotope fractionation during reductive dechlorination can contribute to confirm and quantify in situ bioremediation of these chemicals in contaminated sites containing Dehalogenimonas.
KEYWORDS: Fully automated, Anaerobic bioreactor, Chlorinated ethenes, TCE concept, Large plume treatment
ABSTRACT:
Overview
A special category of soil remediation covers sites that have been contaminated by the use of solvents, especially chlorinated ethenes. These contaminants can be removed by enhanced natural attenuation using the so-called TCE concept. Artificially cultivated bacteria (Dehalococcoides ethenogenes, DHC) with the required carbon source and nutrients are introduced into the soil in order to stimulate anaerobic degradation. The process can be controlled by constantly monitoring the influent, infiltrate and bioreactor streams for pH, oxygen and ORP. The strength of this concept lies in its relatively short active stimulation phase with complete degradation of the chlorinated hydrocarbons to harmless end products.
The general remedial approach involves extraction, amendment and re-circulation of groundwater in the targeted aquifer zone. Extracted groundwater is passed through an anaerobic bioreactor to enrich the water with DHC. After filtration, the feed is infiltrated through injection screens or wells located up gradient of the treated zone. This anaerobic bioremediation approach can be applied in urbanized areas with limited site access to prevent site disruption and reduce impacts to the environment. This semi-passive method can expedite the time of remediation, compared to passive approaches. The fully automated remotely controlled bioreactor system provides clients with a complete biodegradation of chlorinated ethenes.
Specifications
The system consists of a control unit, a bioreactor and a filtration and charging system. Once the DHC inoculum is added to the bioreactor, their growth is enhanced by feeding the system, until a cell count of 105 cells/ml is achieved. Bioreactor operating conditions include ORP levels of less than -300 mV, while oxygen levels are reduced to zero at a temperature of about 20 ºC. The bioreactor operates at an extraction/infiltration flow rate of about 10 m3/hr. Depending on the size of a pore volume for the targeted zone, the system may be able to treat a site within a period of several months. Based on previous experiences, amendment of one pore volume of the targeted aquifer zone is sufficient for complete chlorinated ethenes treatment at most sites.
Process and performance monitoring
Monitoring our process and performance is crucial to the success of the enhanced bioremediation projects. Therefore, defined parameters such as oxygen concentration, pH, water temperature (ºC) and oxidation-reduction potential (ORP) are monitored continuously. When the parameters exceed threshold levels, the bioreactor is automatically switched off. Monitoring wells in the field are used to assess the efficacy of enhanced bioremediation. The design and operation of this in-situ system of extraction and infiltration can be adjusted depending on the volumes of groundwater to be treated, site specific circumstances and remedial targets to be met.
Technology application
Leakages that had occurred, because of a former dry cleaner in the center of The Hague in The Netherlands, left the shallow and deeper groundwater up to 15 m –gl contaminated with chlorinated solvents (PCE and TCE).
Soil properties, in the area of The Hague, are characterized by sediments of medium fine sand and heterogeneous intermediate layers of clay and/or peat. Groundwater contamination plumes had spread to a volume of 400,000 m3 underneath private properties and form a thread for the deeper aquifers and the abstraction of drinking water.
The design by Bioclear opted for a phased approach, with the infiltration and extraction filters all in the public road. The plume was divided into six successive steps which were provided with a carbon source and micro-organisms. After completion of the first phase, the extraction wells of phase 1 were used as infiltration wells for phase 2. This function shift is also applied in subsequent phases, for which a total of 55 wells are placed.
The contaminants are biologically degraded in the subsurface within the course of a few months to a few years at most. After this time the risks will have been removed and we are left with clean groundwater. The location in The Hague is situated in an urban area; even so, the entire remediation system could be placed without problems. All required wells and pipes were placed underground. The remediation unit was on-site for approximately sixteen months. This is very short when compared to more traditional remediation techniques. This also meant that the disturbance to the community was kept to a minimum. Furthermore, this technique is sustainable and environmentally friendly, as it requires very little energy and only natural nutrients are used. In a period of sixteen months, the bacteria and nutrients were introduced into the soil. A large portion of the contamination had already been entirely degraded in that time. The remediation project was therefore a great success.
Conclusions
The TCE treatment results in a complete degradation to ethane/ethane in all the projects.
Using the fully automated telemetric system, it is possible to continuously control the pH, redox and oxygen in the groundwater.
Logging data indicated the working of the TCE unit with minimum human supervision and maximum efficiency.
TCE is a sustainable solution for large plume remediations in comparison to conventional techniques.
The project was completed in time, with no rebound observed and with no cost overruns.
Bioremediation of chlorinated solvents including chlorinated ethenes, chlorinated ethanes and chlorinated methanes in groundwater is a proven remedial approach and has been used widely in Europe and North America for over a decade. In many Northern locations in Europe, the U.S., and Canada low groundwater temperatures are ubiquitous and low permeability matrices are widespread. Technologies that can mitigate injection issues in low permeability matrices and growing experience with low groundwater temperature bioremediation have led to a better understanding of remediation strategies and timelines under these conditions.
Understanding the feasibility of bioremediation and the practical limits of bioremediation of chlorinated solvents under cold conditions is important in remedy selection and expectation management for colder climate bioremediation projects. Groundwater temperatures defined as cold for bioremediation applications (i.e., below 10 ºC) are commonly found in Europe north of approximately 55 degrees latitude including much of Scandinavia, the Baltic Countries and Scotland. In North America cold groundwater is generally found north of 45 degrees latitude in the Northern contiguous US, Alaska and much of Canada. Specific strategies for approaching cold water bioremediation will be discussed including bioaugmentation, electron donor selection and application. Examples of successful bioremediation at cold climate sites in Denmark, United States (Alaska) and Canada, will be presented with a focus on degradation half-lives, concentrations of dechlorinating bacteria (Dehalococcoides) and remediation outcomes.
Low permeability strata are common in some of the most highly industrialized areas of Europe and North America. Low permeability materials pose a challenge for in situ remedial technologies as delivery of the amendments and contact with the compounds of interest can be challenging. Closely spaced injection points using multiple injection intervals per point can aid distribution, but can also be time consuming and costly. Novel technologies, such as Electro Kinetic bioremediation (EK-Bio), can be used to deliver electron donor in low permeability matrices as well as transporting dechlorinating bacteria through the low permeability materials. Hydraulic fracturing, a technique originally conceived as an oil and gas extraction technology, can also be used to improve distribution of bioremediation amendments, thereby improving bioremediation outcomes. Examples of successful implementation of EK-BIO and hydraulic fracturing for bioremediation in clay strata will be discussed.
A metal processing site in Flanders, Belgium is characterized by a groundwater contamination with chloro-ethenes that has migrated 1 km off-site. The groundwater has a high seepage velocity and is acidic. Laboratory tests have shown that enhanced natural attenuation by addition of organic substrate induces partial dechlorination of PCE, which stalls at cis-DCE. The objective of this EU-LIFE+ sponsored project BACAd is to demonstrate that bioaugmentation can be achieved on full-scale in a cost efficient way by optimizing the in-situ propagation of injected cultures.
In a first stage, five microbial cultures which were derived from different sites and two electron donors were screened with laboratory microcosm tests. The two best cultures were used for execution of two push-pull pilot tests. Each test was done with a specific culture and electron donor. Laboratory column tests were performed with these cultures and site materials to evaluate and optimize their migration in the soil. The culture that performed the best in the push-pull and column tests was injected in a pilot test with 4 injection wells. At the same time, a similar field test has been performed in an adjacent area with injection of groundwater from another site where complete dechlorination of PCE has occurred. Afterwards, the remediation has been scaled up to a reactive zone with 40 + 20 injection wells that covers the entire plume width. Full-scale bioaugmentation with transfers of the microbial population from the initial pilot test remediation areas to the reactive zone has started in spring 2014. By doing this, the costs for the production and injection of the microbial culture may be decreased, improving remediation efficiency. The in-situ propagation of microbial cultures is monitored with QPCR and DGGE-analyses.
Laboratory microcosms have demonstrated complete dechlorination with bio-augmentation in the presence of the substrates Nutrolase (a residue from potatoe processing) and glycerol. The column tests confirmed the need for bio-augmentation and the dechlorination capabilities of the two cultures that were used in the field. They have demonstrated the mobility of the cultures in aquifer materials of the site.
The two push-pull test with cultures grown on Nutrolase and glycerol induced complete dechlorination in the field. Acidic groundwater conditions have slowed the process and required neutralization. Glycerol was a better substrate than Nutrolase. The culture grown on Nutrolase was contaminated by pathogenic bacteria, which was caused by the Nutrolase. The in-situ evolution of the pathogens (faecal Streptococci) has been monitored. Results of microbial and molecular analyses by QPCR will be presented.
The first small scale pilot test with injection of glycerol and a microbial culture has achieved complete dechlorination in the injection wells following bio-augmentation. QPCR analyses have demonstrated that DNA of Dehalococcoides and of dehalogenating enzymes has increased consistently over time. Full dechlorination has not been achieved yet in the injection wells of the second small-scale test in which groundwater from another site was injected, although removal of PCE, TCE and DCE has been achieved to a large extent.
The establishment of suitable environmental conditions in the full-scale test area by regular injections of glycerol and bicarbonate has required more time than expected. This was the result of high groundwater velocity, oxidizing redox conditions and an acidic pH of 4. The transfers of groundwater from bioaugmented pilot test areas into the full-scale reactive zone were initiated as soon as favourable environmental conditions were established in the injection wells. They have been ongoing at regular time intervals since spring 2014. The monitoring results will be presented.
Background/Objectives
On July 6, 2013 an unattended train derailed in the centre of the Town of Lac-Mégantic, Québec, approximately 3 hours east of Montréal. The train’s cargo, Bakken North Dakota formation crude oil contained in 74 rail cars, spilled and resulted in multiple explosions with the fire destroying a portion of the downtown killing 47 residents and creating a major environmental disaster. The spill and resultant explosions and fire destroyed over 30 buildings and municipal infrastructure, impacted soils and groundwater in the immediate spill area as well as surface water and sediments in Mégantic Lake and Chaudière River. Following five months of emergency response activities the site has been stabilized, major urban restoration planning has been completed and a soil, sediment, and groundwater remedy is being implemented.
AECOM was contracted by the Town of Lac-Mégantic and the Québec Ministry of Sustainable Development, Environment and Climate Change to design and oversee construction of all remediation and restoration activities. AECOM’s objectives were to: develop and administer a site-wide Health and Safety Plan, Remediation Plan, impacted building Assessment and Rehabilitation Plan, and oversee and report on all spill site restoration and ancillary commercial renovation activities.
Approach
Site remediation consisted of utilizing existing emergency response soil, groundwater and sediment data to develop a remedial strategy, integrate the strategy into infrastructure and building restoration and demolition activities as well as numerous off-site activities all related to the revitalization of Lac-Mégantic. Impacted soil volumes requiring removal and treatment are anticipated to be 400,000 tonnes and all treated soils are required to meet Québec Level A soil standards. Soils from impacted areas within the “zone incendiée” (area destroyed by fire), around remaining building foundations, storm sewer replacement and miscellaneous other related construction activities will be removed and transported off-site to a treatment area. Several treatment technologies were evaluated including ex-situ biological treatment, soil washing and thermal treatment. Enhanced biological treatment and select off-site thermal treatment were selected. Remediated materials will be reused where appropriate in the site-wide restoration. In addition, a groundwater cut-off trench and strategically located recovery wells situated throughout the site collect and transfer impacted groundwater to a stationary carbon-based treatment system. Additionally, Chaudière River and some Mégantic Lake sediments impacted by the spill will be further delineated and removed.
Results and Lessons Learned
The schedule for the remediation is aggressive with some building demolition, infrastructure replacement, soil and groundwater remediation and restoration extending into 2015. As a result, a strategically staged and sequenced plan has been developed with construction beginning in May 2014. The various components of the plan will ensure clean-up of the downtown area to performance objectives, re-design and installation of required municipal infrastructure, successful treatment of removed soil, groundwater recovery, treatment and monitoring, and flexibility to enable future site development in concert with on-going discussions and consultations with the residents of Lac-Mégantic.
This presentation will provide an update on restorative construction activities, overview of the application of innovative and sustainable remedial technologies and approaches, and provide the basis for the vision of the future of Lac-Mégantic.
Combined Remedy Benefits of Integrated Physical, Chemical and Biological Treatments on a 14 Million Litre Fuel Spill in a Swedish Forest
Kristin Forsberg (kristin.forsberg@rgs90.se) RGS 90, Malmö, Sweden)
Jonny Bergman (jonny.bergman@rgs90.se) (RGS 90, Göteborg, Sweden)
Gareth Leonard (gleonard@regenesis.com) and Jeremy Birnstingl (Regenesis Ltd, Bath, UK)
Background/Objectives. A series of historic spills from a Swedish military storage depot led to an extensive area of groundwater under forest and commercial property being impacted with petroleum fuels. The largest spill event was an explosion resulting in a loss of life and the release of 14 million litres of petroleum products that reached the wider environment, covering an area of approximately 45,000m2. The problem was enhanced by the difficult terrain, which largely consisted of a hillside moraine and boulder fields covered with dense vegetation. An integrated in situ treatment approach proactively combining physical, chemical and biological technologies both spatially and in sequence was selected, with the combined application presenting clear time and cost benefits over the projected use of any one of the technologies used alone.
The principal pollution incident occurred in 1958 following an explosion. 14,000,000 L of gasoline, diesel and jet-fuel were released and flowed down the forested mountainside and into a lake. The initial 1950’s clean-up activities included setting the lake on fire, with the remaining free-product ‘lake’ on shore then covered with soil, left in place and used as a playground.
Approach/Activities. Contemporary remedial options considered have included excavation, multi-phase extraction, in situ chemical oxidation (ISCO), bio-sparging and enhanced natural attenuation. Following costing and feasibility evaluations, integration of physical, chemical and biological technologies both spatially and sequentially was been identified as the most cost-effective and flexibly adaptive strategy. Pilot tests of the component parts (selected as compatible) were conducted separately to identify optimal efficiency bands and dosing requirements, and from this, the spatial arrangement of technologies and sequential switch-points for optimal efficiency were determined. The first stage of full-scale application was conducted through winter of 2013-14. Performance validation (at time of abstract; 6 – 8 months) describes concentration reductions of >95% to non-detect through the majority of the areas treated.
Results/Lessons Learned. Identification of optimal bands of application based on pilot study performance and cost-projection enabled each technology to be applied at its maximum efficiency, providing an overall ‘treatment-train’ synergy. The projected cost of integrated technology application was calculated at between 25 – 55% of the cost of any of the same technologies used alone, representing cost savings of between $1.7M – $6.5M on the overall project. The projected time for completion was also shortened by several years, although the actual extent of this is harder to reliably determine. In the final design, excavation was not required. The remediation left no visible impacts; important both for aesthetics, military security, and macro-environmental impact – the forest was left in place.
This talk provides qualitative and quantitative examples of the cost and practicality benefits that may be secured through proactive technology integration by way of a large, multi-faceted, formal case study. It is anticipated that this talk will be of interest to end-users, remediation practitioners and regulators alike.
The presence of DNAPL is often limiting factor for the removal of chlorinated aliphatic hydrocarbons from the subsurface. Residual DNAPL usually results in the rebound effect causing repeated increase of contaminants concentrations. Surfactants (surface active agents) are chemical compounds with specific molecular structures typically composed of a strongly hydrophilic head and a hydrophobic tail. In a DNAPL-contaminated aquifer, this specific property of surfactants can increase DNAPL solubility and lower DNAPL-water interfacial tension to the point that physical mobilization takes place. Application of surfactants thus can enhance the remedial action. Surfactants flushing is a mature technology in the petroleum-engineering field. The technology has been shown to be effective also for DNAPL sites recently. A surfactant flushing system typically consists of a network of injection and extraction wells. A mixture of injected fluid and mobilized contaminant is captured through extraction wells that requires further treatment. This treatment could be technically demanding (e.g. due to the tendency of surfactants to form foam). Considering that coupling of surfactants application with another remedial technology seems to be suitable. In-situ chemical oxidation (ISCO) is promising technology for the combination with surfactants. In addition, the main weakness of ISCO application to treat DNAPL thus could be solved.
The pilot test of combined application of surfactants and ISCO was performed at the DNAPL-contaminated site in the western part of the Czech Republic. From the geological point of view, the site bedrock is formed by mica-schist. The shallow aquifer is bound to the zone of weathered bedrock and overlying sandy to clayey loams. The aquifer permeability is relatively low represented by hydraulic conductivity of 10-6 to 10-7 m/s.
The test comprised three phases: 1) separate application of surfactant (i.e. without subsequent injection of oxidant); 2) separate application of oxidant (i.e. without preceding application of surfactant); 3) combined application of surfactant and oxidant. Concentrations of chlorinated aliphatic hydrocarbons, surfactant and other relevant parameters were monitored during the pilot test.
The application of surfactant resulted in the multiply increase of concentrations of chlorinated hydrocarbons (up to 13 times) confirming the efficiency of surfactant to mobilize the residual DNAPL. The subsequent injection of oxidant showed immediate reduction of chlorinated hydrocarbons mobilized by surfactants.
The results of pilot test indicate the applicability of combined use of surfactants and in-situ chemical oxidation at the DNAPL-contaminated sites but also some limitations of this approach.
The performed work was granted by Czech Ministry of Industry and Trade.
The context
Halton Borough Council (HBC) is procuring a £686M road crossing of the River Mersey between Widnes and Runcorn, known as the Mersey Gateway Project, one of the UK government’s Top 40 priority projects in the National Infrastructure Plan. Part of the advance works has been the remediation of Catalyst Trade Park, a 5.6ha site to be covered by an embankment and road junction associated with the new bridge.
The challenge
Historically, the site was an alkali works and then ICI’s ‘Widnes Experimental Site’. It was
contaminated with chlorinated solvents (at concentrations so high ‘neat’ solvents were
present), arsenic and radioactive materials. These contaminants posed significant cost and
programme risks if remediation was left for the main construction works. The remediation was a ‘critical path’ item so completion on time and prompt ‘sign off’ were key expectations of HBC and Merseylink, the Preferred Bidder. The remediation had to be delivered between
central Government conditional financial approval and ‘financial close’. Given the complexity of the site’s geology and the technically challenging nature of the contaminants a goal of ‘betterment’ rather than ‘target’ values was successfully negotiated by Ramboll with the regulators.
The solution
Without set targets to achieve, the problem for the project team was to achieve and demonstrate ‘betterment’ to the regulators within a specific timeframe. Ram,boll’s approach to this problem enabled a previously challenging concept, remediation of chlorinated solvents, to be delivered at considerably lower risk in terms of certainty, costs and programme. Ramboll and Celtic (the remediation contractor) designed, installed, then successfully demonstrated that substantial “betterment” had been achieved. This resulted from technical excellence through innovation, flexibility and optimisation in design with the technical deployment of a combination of remediation techniques, the complex nature
of the site and the contaminants, including the ‘neat’ solvents, meant that a simple “off-the-shelf” remediation solution would not suffice. Celtic and Ramboll collaborated closely with HBC and the regulators to develop the remediation solution that combined the efficiencies of four separate techniques (groundwater abstraction, multiphase extraction of contaminated water, vapours, in-situ chemical oxidation and ‘neat’ solvent recovery) to achieve the maximum and most cost effective mass recovery possible within programme. ‘Betterment’ was maximised by continuously monitoring performance parameters and site conditions so that the system could be optimised and adapted as changing circumstances required. The regulators were invited to attend monthly progress meetings and encouraged to become
part of the ‘project team’, steering the works to a successful conclusion.
Design/Performance
An innovative remediation system was designed to recover technically challenging solvents;
combining the efficiencies of four techniques to achieve the required balance of ‘neat’ solvent
recovery and groundwater treatment, integrated into a single highly flexible and adaptable system. Performance parameters were automatically measured and relayed to the team and the system was continually adapted to maximise the ‘betterment’ achieved. Whilst the system focused on treating groundwater and soils, a secondary system was used to recirculate treated groundwater and encourage ‘neat’ solvent into recovery wells where
it could be extracted. The system proved very successful and ‘neat’ solvent was identified within a week of commencing operations. Whereas initial expectations were that hundreds of kilos of solvent might be recovered, 17 tonnes were ultimately extracted, significantly exceeding the regulator’s expectations. Multi-phase extraction was used to aggressively recover neat solvents from the base of treatment boreholes. The success of the system was measured against the goal of achieving ‘asymptotic’ conditions in terms of recovery of solvents, to demonstrate maximum practicable recovery.
Benefits
The main benefit of undertaking sustainable remediation was recovering a significant volume
of a highly toxic persistent contaminant, improving groundwater quality and reducing environmental risks to the River Mersey and to local people. Secondly, the remediation works successfully unlocked the site development constraints allowing the development to proceed. Also, significant cost and time delays to the project were avoided by ensuring that the Regulator did not designate the site as a ‘Contaminated Site’ under Part IIA regulations.
The “Fixed price” gave economic certainty to HBC. In turn HBC gained the advantage of
significantly reducing (effectively removing) the ‘risk price’ the Preferred Bidder might have put against the contamination issue which was expected to have been many times greater than the £2.2M cost of the remediation. The early completion also removed a significant potential programme risk from the Project. During 14 months, 90% operational time was
achieved based on 24/7 working. The work was delivered on budget within the strict programme. Ultimately regulatory sign-off was achieved within a week, as Regulators had confidence that the remediation work was completed diligently. The pro-active approach adopted in implementing the remediation design enabled a robust approach to health and safety to be maintained during high profile works. The benefits that this delivered included no lost time incidents during the entire programme. Celtic was awarded “Performance beyond Compliance” certification under the Considerate Constructors Scheme and their approach to H&S was commended by the CDM-C.
The remediation of aged source zone affected by residual chlorinated solvents DNAPL represent one of the main challenge in aquifer contamination. When biological reductive dechlorination is considered as a feasible remediation approach, effective delivery and distribution of electron donors other than bioavailability of contaminants in heterogeneous aquifers are some of the primary limitations in most hydrogeological settings. Traditional injection approaches are often limited by preferential migration of injected fluids through better permeable zones, while delivery through less permeable and contaminated layers is usually limited.
By this regards, Groundwater Circulation Wells (GCWs) could advantageously improve the distribution of soluble electron donors by creating a three-dimensional groundwater controlled circulation pattern, especially efficient in anisotropic settings where significant differences exist between horizontal and vertical hydraulic conductivity.
In this work we report on the remediation activity carried out at an operative industrial site in North Italy, heavily contaminated by different chlorinated aliphatic hydrocarbons, including 1,1-DCA, TCE, 1,2-DCE and VC at concentration up to 100 mg/L. The site is characterized by the presence of a persistent source zone in an hydrogeological complex saturated zone characterized by fine to middle sands with intercalation of less permeable sandy silts to clayey silts layers.
Microbiological characterization by FISH and qPCR techniques along with results from extensive microcosm investigation with different electron donors have clearly indicated the possibility to enhance the active biological reductive dechlorination (RD) until the complete dechlorination of the occurring CAH to ethene. Among the different tested electron donors, poly-hydroxy-butyrrate (PHB), a biodegradable polymer easily fermented to volatile fatty acids and molecular hydrogen, have been experimentally verified as effective in stimulating biological RD at the investigated site. Moreover, coupling biological RD with ZVI have been considered and tested as the option to efficiently remove the spectrum of CAH present at the site.
Based on the laboratory investigation and site characterization, a 30 meter deep GCW, with three screen sections, was designed and installed at the site for a pilot testing. Groundwater is pumped, at a rate up to 2.5 m3/h, towards two screen sections of the GCW and is reinjected into the aquifer by another screen section after passing through an above ground installed PHB (releasing electron donor) and ZVI reactor. The pumping rate can be adjusted to the progress of microbiological remediation and also the spreading of biostimulants in the subsurface can be varied. For sampling purposes and to monitor the remediation progress two Multilevel Sampling System (MLWS) and a multi cluster well are installed in the sphere of influence of the GCW .
Key performance issues from hydraulic, technical and operational standpoints will be discussed and evaluated during the presentation.
Often brownfields re-use is considered in the context of hard re-uses such as for housing, business parks or infrastructure. Soft re- uses, such as for green space or biomass production, can tend to be overlooked. However, soft re-uses can provide services which enhance regeneration, both in their own right and when integrated with hard uses such as for buildings.
Depending on design, some examples of these services are:
• Provision of open space in urban areas of in and around new development areas, which brings benefits for well-being, health, leisure and sense of place,
• Providing green infrastructure and services related to mitigation of heat island effects, mitigation of urban air pollution, flood protection, water storage and encouraging habitat and wildlife
• Supporting the renaissance of and innovations in urban gardening, community gardens and urban farming increases demand for urban brownfields
• Supply of renewable energy and other environmental services (such as sustainable urban drainage).
A range of interventions might be used to deliver these services, in domains such as:
• Soil Management
• Water Management
• Implementing Green Infrastructure
• Gentle Remediation Options
• Other Remediation Options
• Renewables (energy, materials, biomass)
• Sustainable Land Planning and Development.
Some services may generate revenue in their own right, some may be important assets to support public investment in regeneration, and some may have direct or indirect impacts on the value of built redevelopment (for example providing a framing which enhances property values, or providing local energy supply or other environmental services). Regeneration / redevelopment projects that deliver a broad range of services have both improved overall sustainability and enhanced economic value.
HOMBRE (Holistic Management of Brownfield Regeneration) was a major EU FP7 project which concluded in November 2014 (www.zerobrownfields.eu). One of its outputs is a simple design aid to help developers and others involved in brownfields to identify what services they can get from soft reuse interventions for their site, how these interact and what the initial default design considerations might be. HOMBRE’s “Brownfield Opportunity Matrix” is a simple Excel based screening tool that essentially maps the services that might add value to a redevelopment project against the interventions that can deliver those services. It maps the prospective range of opportunities that might be realised by a brownfield redevelopment project and the project’s consequent sources of value. For each opportunity there is a hyperlink to additional information, including a case study. There is also supporting information to describe the various services and interventions listed in the matrix.
This mapping identifies where there are strong synergies between interventions and services, and also the relatively infrequent occurrences of antagonism. Wherever a particular intervention delivers a service, this interaction creates an opportunity to add value. The matrix describes the kinds of value that each opportunity might generate, namely:
• Revenue Generation: for example capital value uplifts, or income opprotunities for example from renewable energy or leisure
• Natural Capital: developed in a number of ways, including (but not limited to) providing green infrastructure, improvement of the local climate, improvement of water resources and mitigation of contamination (protecting and enhancing local ecosystem/environment).
• Cultural Capital: developed by improving the social environment (by improving the aesthetics of an area and/or creating a sense of place/belonging for e.g.) and can be a direct result of an increase in natural capital.
• Economic Capital – tangibles: e.g. increase of land and property values in the area (feeding back into Cultural Capital) providing benefits to the local community and also the investor.
• Economic Capital – intangibles: benefits that are immeasurable but can include for example, an improvement of the image of the investor (be it a company or individual).
Overall the brownfield opportunity matrix can:
• Support initial identification or benchmarking of soft re-use options for brownfields at early stage
• Support exploratory discussions with interested stakeholders
• Provide a structure to describe an initial design concept, in support for example of planning applications
• Provide a structure for more detailed sustainability assessment of different re-use combinations, and similarly for cost benefit comparisons.
The presentation will explore a benchmarking application using a worked example.
The final countdown.
“Successful remediation policies leads to the end of the Dutch Soil Protection Act”
The Dutch decentralized soil remediation operation is successful in remediating all top-priority locations and will result within 5 years in the withdrawal of the Soil Protection Act. After remediating the top-priority locations (the final countdown) legislation for dealing with remaining soil and groundwater contamination in a more integrated approach will be incorporated in the Environment and Planning Act.
The Dutch Policy on soil remediation has its origin in the early ‘80’s of the 20th century when the first scandals in soil contamination became apparent. In the small town of Lekkerkerk a residential area had been built upon a former industrial dump site and indoor air concentration of Benzenes caused health problems. This triggered public awareness, inventory programs and soil protective policies.
The Dutch soil Policy evaluated from a strict preventative policy and a foresight of total multifunctional clean-up of all contaminated sites in the ‘80s towards a more realistic policy which remained strictly preventative but amended the clean-up ambitions towards functional remediation of heavily contaminated sites. This resulted in the remediation of sites that had to be remediated for other reasons than the environment (i.e. the redevelopment for housing on former industrial sites) and therefore left urgent sites abandoned and not remediated.
In order to focus the remediation effort, the Dutch government in close collaboration with the competent authorities on soil remediation (the provinces and larger municipalities) established in 2009 a 5 year program. This program for 700 Million Euro had the aim of remediating all locations with urgent risks for humans and an inventory of all other locations with urgent risks for spreading of contaminants or the ecology.
This program is now finished and has proven to be very successful. Locations with urgent risks for humans are being remediated and the inventory of other urgent locations is finished. This resulted in a list of approximately 1500 locations with urgent risks for spreading of contaminants and urgent risks for the ecology. Human risks with top-priority are dealt with, groundwater contamination still is a top-priority. Groundwater contamination is more complex to deal with and needs instead of a site specific approach a more area based integrated approach where other interest such as heat and cold storage in the aquifer have to be taken into account. Groundwater as a resource for drinking water and (food and drink-)industry is a very important economic factor, therefore the current program needs to be extended.
The Dutch government, provinces, water boards, municipalities and involved private parties are now drawing up a new 5 year program with the aim of dealing with these 1500 locations and establishing new legislation for the period after this final countdown. When all urgent locations are dealt with, soil remediation can be integrated in the regular spatial planning processes. In the future soil remediation in the Netherlands will no longer be a stand-alone process but will only occur as a side effect of developments or in case the ecosystem functions of the groundwater are under pressure. Therefore the Soil protection Act will be withdrawn in 2018 and legislation on dealing with historic soil and groundwater contamination will be incorporated in the new Environment and Planning Act.
The full article will describe in detail the results, success and fail factors of the 2010-2015 program. What can be learned from the Dutch decentralized operation and the successful focus on priority locations? The full article will also describe the outline and organization of the 2016-2020 program and will answer the question why private parties will also be involved. Furthermore the full article will provide an outline of the new soil legislation which will be incorporated in the Environment and Planning Act.
Introduction:
In order to ensure knowledge of contaminated soil, regional authorities in Denmark register contaminated properties. The Region screens all properties with known activities that can have lead to contamination and registers those which are suspected to be contaminated. The Region pays for the environmental study and remediation of old contaminated sites, where no one can be held accountable in the present. This is a huge and expensive task, necessitating prioritization among contaminated properties situated upon valuable groundwater areas and recognition of the fact that some properties will never be remediated.
The process of studying properties with former possibly contaminating activities is ongoing, and the Region notifies all owners by letter, when a property is added to the contamination-register. This official register ensures that the knowledge is available and disclosed, when you buy a property. Everybody can look up any property to see if it is registered as (possibly) contaminated.
Danish legislation – the law for soil contamination - ensures that you must have permission to carry out construction on contaminated properties. I.e. when a property is in the contamination-register, you must apply for permission to build houses, schools and parks and you must ensure that the building-project does not lead to (further) contamination of groundwater and surface water. Permission is given by the municipalities, and the Region is always consulted before the final permission is given, to ensure that the contractor does not leave contamination, that the Region will have to remediate at a later stage in order to protect the groundwater and surface water.
The role of the Region:
The role of the Region is to ensure that no building is placed directly above a known contamination, which will make a future remediation of the groundwater and surface water more difficult and expensive. In the collaboration between the municipalities and Region, the Region is both a partner and an authority.
The Region is a partner, when we and a municipality discuss different solutions and techniques and what terms to set in a construction permission. The goal is to achieve solutions that are durable for the lifetime of the building. The Region must therefore at all times be up to date with the latest knowledge and techniques. The solutions must ensure that residents do not have physical contact with contaminated topsoil and that they have good indoor- and outdoor climate in their new home and surrounding garden.
The Region is the authority for groundwater protection and must ensure that building-projects do not lead to contamination of groundwater. E.g. if removal of concrete and asphalt from an old industrial property are proposed, contaminated soil may be revealed, causing groundwater contamination by percolation. In this case the Region emplaces certain terms to be upheld in a construction permission.
Case introduction:
The administrative procedures are illustrated through a case of current construction of an apartment block on a contaminated site in Copenhagen.
The terms in the permission given to build the apartment block, required the owner of the contaminated site to perform investigations based on past activities deemed to potentially have contaminated the soil at the site. Results from these investigations showed high levels of soil and groundwater contamination on the site. According to the permission, the high levels of soil contamination had to be cleaned up, before the building activity could begin, as risk assessment showed that the contaminated soil would otherwise constitute a health hazard to the residents in the new apartments as well as an environmental hazard.
After cleaning up the high levels of contaminated soil there were still high levels of groundwater contamination at the site, and a renewed risk assessment showed that vapor intrusion from the contaminated groundwater could still be a health hazard to the residents. Consequently, according to the permission, the building will be established with ventilation beneath it. The contractor has submitted a proposal for the ventilation system and the Municipality of Copenhagen and the Capital Region of Denmark will collaborate on evaluating the proposal to secure the safety of the residents both short and long term with a solution that is robust enough to ensure that no further measures have to be taken at the site.
Conclusion:
The consequences of the soil contamination law and register are:
• for the contractor - the process of building new houses some time takes more time, because of the sampling, removal of contaminated soil and building precautions. They know this when they buy the property, and it is reflected in the price of the property.
• for the people, who buy an apartment - insurance of a healthy indoor- and outdoor climate and insurance that the topsoil is uncontaminated.
• for the Capital Region of Denmark - a contaminated site, where indoor and outdoor climate and topsoil have been secured. I.e. the only possible remaining effort is the groundwater, which the Region can prioritize according to regular procedure.
Objectives
Sustainable redevelopment of large and complex brownfield sites has become a major challenge for urban regeneration policies. The REFRINDD project (Sustainable Brownfield regeneration Approach [2012-2015]) has developed an integrated approach for the sustainable remediation and urban redevelopment of complex contaminated brownfields sites. The project is partly funded by the French Environment and Energy Management Agency (ADEME).
Brownfield redevelopment projects often involve stakeholders with multiple and conflicting objectives. One of the project objectives is to deliver an approach that will assist elected representatives, local authorities and urban agencies in planning and managing sustainable brownfield regeneration projects. The project aims at developing a practical guidance and a multi-criteria analysis (MCA) tool to help these stakeholders discuss, assess and choose the most-fit for purpose redevelopment scenarios, in a transparent decision process. The project specifically examines industrial brownfield sites with contamination issues, which often combine poor environmental status with low social appreciation, and therefore bringing these sites back into beneficial use is a complex challenge.
Method
The development of practical guidance and accompanying MCA-tool involved the following tasks:
•Consultation with a wide range of French stakeholders (e.g. urban planners, landscape architects, contaminated land consultants, project managers);
•A systemic analysis of the relationships between the stakeholders and the data they exchange when delivering a regeneration project;
•An extensive literature review on methods, tools and criteria for assisting in integrated and sustainable approaches of brownfield regeneration;
•Specific interviews with relevant stakeholders involved in on-going brownfield regeneration projects.
Results and discussion
Stakeholder consultations helped identify the main challenges they face and the need for an integrated approach for assisting in sustainable brownfield redevelopment. The analysis of relationships between stakeholders and data exchange, helped listing and classifying data that is available, useful or missing in various typologies. Using the systemic information and communication theory, the stakeholder’s relationships were modeled. Data collection, historical memory and data transmission were noted as main areas where improvements are needed [1].
The review of stakeholder needs led to proposing a 6-step method for sustainable redevelopment of industrial and contaminated brownfield sites in France [2, 3, 4]. The iterative 6-Steps framework attempts to take into account a complex decisional making process, as follows:
•Step 0, Sustainable ambitions - collect sustainable ambitions on the site from elected local officials;
•Step 1, Project vision - understand the needs for redevelopment in the area and define initial redevelopment project;
•Step 2, Integrated analysis of opportunities and restrictions - define the project outline and feasibility assessment;
•Step 3, Planning and design - develop the final redevelopment program document;
•Step 4, Implementation - complete the redevelopment works and undertake final costing;
•Step 5, Review and make adjustments where necessary.
For each step, a key objective; spatial and time scale; specific beneficiaries and users; and themes to assess/discuss are provided. The requirements of supporting tools were identified for each of the 6 steps, in particular whether MCAs were needed. A prototype MCAs tool was then developed using Excel® software. It follows the ‘6 Steps’ approach and its main benefits assist in:
•Discussing and deciding the sustainable ambitions for developing a site and the constraints associated with the site;
•Assessing and choosing the most ‘fit for purpose’ redevelopment scenarios, taking into account the sustainability objectives and economic constraints (providing specific graphs for visualisation and discussion purposes).
The criteria provided in the MCAs are grouped into 15 recurrent themes. Some of the criteria are common and some are very specific depending on the step being considered. The MCAs enabling a sustainability review of the planning programme require information on the final chosen remediation for each considered brownfield sector.
Perspectives
French stakeholders have confirmed their need for an integrated approach to manage large and complex brownfield regeneration projects. Their recommendations, integrated into a project research, helped identify the MCAs and relevant criteria required to assess the delivery of successful projects. The REFFRINDD approach and the various MCAs are currently being tested in three on-going French brownfield revitalisation projects. The approach and a pilot MCA tool are to be delivered at the end of 2015.
[1] Valeyre, T., Vimond-Laboudigue, A., Alary, C., Laudati, P., (2013). Improvement of data collection, treatment, interpretation and diffusion in brownfield revitalization, in Innowacyjne rozwiązania rewitalizacji terenów zdegradowanych, Fundacja Ekonomistów Środowiska i Zasobów Naturalnych, 261-270
[2] Limasset, E., G., Zornig, C., A., Alary, C., Fourny, S., Collet, J-L., Laboudigue, (2014), Intégration des critères de développement durable relatifs à la requalification d’une friche dans la méthodologie REFRINDD et développement d’outils d’aide à la décision, BRGM/RP-63782-FR
[3] Limasset & al, Conference proceedings, Cabernet (2014), Tailored & Sustainable Redevelopment towards Zero Brownfield, October 2014, p74
[4] Limasset & al, Conference proceeding, ADEME, (2014), 3e rencontres de la recherche sur les sites et sols pollués
Joan Krogh, Morten Størup and Søren Helt Jessen
NIRAS, Alleroed, Denmark (jkh@niras.dk)
Abstract:
As a result of urbanization, urban development projects as well as sewer and cable work, large amounts of soil are relocated each year. Typically, soil is considered a waste product and often moved out of urban areas and transported several kilometers away from the origin. Instead, uncontaminated gravel materials obtained from mining pits replaces the soil.
Sustainable soil management must include the economic benefits for the construction business, the reduced inconvenience of soil relocation (i.e. CO2 emissions from transport, noise and heavy traffic in urban areas) as well as taking the environmental benefits of recycling both clean and slightly contaminated soil into account.
This paper will be based upon specific solutions for and challenges by local management of soil. This includes, options for reuse of topsoil on agricultural land; temporary storage (i.e. as soil piles) at empty sites in urban areas; ex-change of soil between individual construction projects, this includes description of a ‘possibility catalogue’; and processing of soil and its geotechnical properties. Furthermore, the paper gives examples of innovative solutions for the recycling of soil for i.e. park mounds, ‘health landscapes’ and climate protection.
It is important that the solutions is based on practical risk-oriented solutions, as these most likely to have the same usability across borders. Focus of this paper will be on the technical possibilities, which will be described through soil processing techniques and survey methods; thus, not the legalistic of Danish law. Practical solutions are described; i.e. the clarification of the strategic possibilities for alternative handling of the soil. Finally, the process related challenges are addressed in terms of timetables and not the least the responsibility for the soil at different times.
Background:
Over the next 20 years, numerous large construction projects will be carried out in the Capital Region (Region Hovedstaden) of Denmark; this includes construction of hospitals in urban areas, new highways, railway development and a whole new city in a rural area. During all these projects, great volumes of soil are to be handled. The Capital Region has a desire to minimize the amount of soil that is transported around the country and increase the amount of soil that is recycled. Thereby changing the perception of soil from being a waste product to a resource. The project is resolved in collaboration between a collective construction industry – The Danish Association of Construction Clients (DACC; Bygherreforeningen), NIRAS A/S, Grontmij A/S, municipalities, contractors, developers and analytical laboratories in Denmark.
The objective of the project is to contribute to new ways to manage excess soil from construction projects, whether it is clean or contaminated, thereby improving sustainability.
The project is in its latter half and the final products are taking shape. Thus, in spring 2015 the lessons learned and experiences gained since 2012, when the project began, can be presented.
The project includes nine sub-projects:
1 Approval of soil collectors; a project, which describes how to implement a system for approval of collectors in order to create a more uniform description of the soil.
2 Planning approaches; a project, which bring together experiences and tools to make it possible to consider alternative soil management possibilities as early in the process as possible.
3 Local soil management; a project that focus’ on the necessity of finding local soil piles, used for temporary storage to even out the temporal differences between projects that can utilize excess soil.
4 Portal for soil; a project, which creates an online platform for trading soil.
5 Processing techniques; a project, which has collected information regarding five difference techniques for processing of soil.
6 Excess soil on agricultural land; a project, which describes the possibilities for usage of excess soil in food production.
7 Health landscapes; a project, which uses soil mounds to advance health; i.e. by establishment of running routes and bike paths on the mounds.
8 Climate adjustment; a project, which uses excess soil from a construction site of a new district in Hillerød, Denmark, to manage water flow during extreme rain events.
9 Energy and excess soil; a project, which describes the possibility of reuse of excess soil to establish energy reservoirs.
Together, the sub-projects create an investigation and an idea development in relation to management of excess soil, which has echoed through all of the Danish construction industry.
Workshop on groundwater contamination from pesticide point sources
- Knowledge exchange on extent of problem, site investigation, risk assessment and remediation of pesticide contamination arising from point sources
Session organizers: Ida Holm Olesen, Head of section, Region of Southern Denmark, Nina Tuxen, Ph.D, Orbicon, Poul L. Bjerg, Professor, Department of Environmental Engineering, Technical University of Denmark.
Contact person: Ida Holm Olesen, e-mail ida.h.olesen@rsyd.dk, phone 0045 7663 1926.
ACS-theme: 1B. Risk assessment and management
Main idea of the session: Pesticide contamination of groundwater is a common challenge for the European countries. The aim of this session is knowledge exchange and mutual inspiration on the topic of pesticide point sources. Ideally, the session will facilitate forming of new European partnerships on further research and development among authorities, consultants and researchers. The theme session will include the latest research findings on pesticide-point sources.
Background:
In Europe, 70% of drinking water is based on groundwater resources, and in Austria and Denmark drinking water is almost entirely sourced from groundwater. The low value of 0.1 μg/L for individual pesticides as the drinking water standard in Europe implies that water used for production of drinking water has to be of high quality.
Pesticides are among the most widespread contaminants in the European groundwater, and they pose a multifaceted environmental challenge with regard to source identification, investigation, risk assessment and remediation. There are many sources to pesticides in the groundwater, but recent findings in Denmark indicate that between 20 and 45 % of the pesticide findings in the groundwater can be attributed to point sources such as old landfills, plant nurseries, farm yards and sites associated with the preparation and cleaning of pesticide spraying equipment as well as accidental spills.
Pesticide contamination from point sources often consists of a mixture of pesticides ranging from compounds introduced on the market in the 1950ties (e.g. phenoxy acids, triazines) to newer compounds such as isoproturone and bentazone.
The number of potential pesticide-point sources in Denmark is unknown, but a worst case scenario suggests more than 10 to a 100 thousand potential sources with many different pesticides. However, previous experience indicates that only a small number of these sources present a real problem, because the concentrations and contaminant fluxes are low for the majority of sites. In Denmark we are facing the challenge of finding “the needle in the haystack” – identifying the point sources that threaten the groundwater and requires remediation. Danish researchers, authorities and consultants have worked on this for several years, and we have developed a series of innovative tools for data analysis, catchment scale risk assessment and remediation. We believe we are on the right path, but we are very well aware that we have not yet found the recipe for efficient management of pesticide-point sources.
Judged by the limited amount of literature on pesticide point sources available, it seems that other European countries are in a similar situation. Therefore, we suggest this theme session to stimulate knowledge sharing, and identification of approaches for new and improved management of groundwater contamination by pesticides.
Format of session
We suggest a double session of 180 minutes total.
We suggest a workshop where all participants are invited to contribute to knowledge exchange by brief presentations and participation in discussions on key issues. To facilitate this, the programme of the session should contain ample time for discussions in smaller groups as well as plenary discussions. Ideally, the participants should register for the workshop in advance in order to enable preparation of brief presentations and forming of discussion groups before the session starts. If this is not possible, informal presentations will be possible and groups will be formed during the session.
The session can be shaped in cooperation with the AquaConSoil organizers in order to obtain the maximum benefit for all parties involved. If the organizers wish to have a more traditional setup with more platform presentations, we suggest replacing the group discussion with case studies on pesticide-point sources.
We are aware that at least two other Danish abstracts regarding pesticide-point sources have been submitted to the conference. Should they – or other abstracts on the subject - be selected for presentations at the conference, we would be happy – if possible - to integrate them in this session.
Programme: timeframe (minutes), titles of presentations and names of presenters:
5: Introduction to the workshop, Poul L. Bjerg
10: Ice breaker in the groups: The participants introduce themselves to each other
20: Pesticides in the environment –sources, pathways, receptors and environmental challenges, Poul L. Bjerg
10: Challenges related to pesticide point-source contamination of groundwater, Ida Holm Olesen
20: Finding the significant pesticide-point sources – an overview of approaches available, Nina Tuxen
25: Short presentations from other European countries
15: Group discussion
10: Plenary discussion
20: Remediation technologies for pesticide-point sources Katerina Tsitonaki, Orbicon
25: Group discussion – identification of new tools and management approaches and needs for development? (The discussion will be supported by a number of pre-prepared questions)l
20: Plenary discussion and summary of the session, Poul L. Bjerg
Moderator of the session: Poul L. Bjerg
Since the second half of the 19th century, industrialization has produced many contaminated areas all over the world. The most common approach to manage these areas has for long time been based on prevention of unacceptable risks to human health and the environment. Over recent years, a number of initiatives across the world have begun applying the sustainable development principles to the management of contaminated sites. These include sustainable remediation forums in: Italy, UK, USA, Canada, Australia / New Zealand, Brazil, Taiwan and other countries, as well as international networks such as the European stakeholders’ networks like Common Forum on Contaminated Land and NICOLE (Network for Industrially Contaminated Land in Europe). Since 2010/11 this thinking has begun to crystalize into a number of “frameworks” for defining and applying sustainable remediation. While there is a remarkable degree of consistency in the approaches proposed by these initiatives, there are differences in detail and emphasis.
This contribution compares frameworks or related forms of guidance from 10 different sustainable remediation initiatives worldwide, describing similarities and differences and identifying general trends in the proposed approaches. The comparison is performed on the basis of a set of criteria which were drawn from the structure of the emerging ISO descriptive standard on sustainable remediation (ISO, 2014. Committee Draft ISO/CD 18504: Soil quality - Guidance on sustainable remediation. TC 190/SC7/WG12. Dated 19 September 2014). The comparison criteria are: definitions, principles, framework structures, context, assessment approach, provision of terminology/vocabulary, case studies, dealing with stakeholders, documentation and recordkeeping.
An initial comparison was made on the basis of the framework documents alone, and then including directly related supporting documents. These comparisons are based on analysis of the written wordings of the documents.
Initial outcomes suggest that there is a general consensus across the initiatives on what sustainable remediation is considered to be. Initiatives share also a common perspective that sustainable remediation can contribute to sustainable development and community resiliency. Some differences emerged when comparing how initiatives suggest this contribution to sustainable development can be given. Different contexts, characterized by different legal frameworks, assumptions, circumstances, facts and stakeholders involved, influence the approaches to sustainable remediation recommended by the initiatives.
Preliminary findings are being shared with members of the various networks via the “SURF international” quarterly meetings they hold managed by CL:AIRE in the UK (www.claire.co.uk/surfinternational). The study also includes feedback from the various international initiatives on the various similarities and differences found from the actual wordings. This exercise is intended to find out whether these differences are real (intentional) or perceived (not intentional), and why any differences may have occurred.
(Note: As a result of this feedback exercise other authors may be included in the full paper).
Practical Application for the SURF-UK Tool Kit: Sustainability Management Practices
Paul Bardos (1), Brian Bone (2), Richard Boyle (3), Frank Evans (4*), Nicola Harries (5), Trevor Howard (6) and Jonathan Smith (7)
1. r3 environmental, Reading, UK; 2. Bone Environmental Ltd, Chipping Campden, UK; 3. Homes & Communities Agency, Bristol, UK; 4. National Grid Properties*, Warwick, UK; 5. CL:AIRE, London, UK; 6. Environment Agency, Bristol, UK and 7. Shell Global Solutions, Rijswijk, The Netherlands.
*Corresponding author. Frank Evans, National Grid Property, National Grid House, Warwick Technology Park, Gallows Hill, Warwick, CV34 6DA E-mail: frank.evans@nationalgrid.com
The aim of this presentation is to inform about the new practical tools that SuRF-UK has developed to help to undertake a sustainable remediation assessment. It is particularly targeted at site owners/managers and service providers (consultants contractors), regulators and authorities.
The UK Sustainable Remediation Forum (SuRF-UK) was established in 2007 to support the application of sustainability principles for remediation in the UK. It is a collaborative, multi-stakeholder initiative co-ordinated by CL:AIRE with a Steering Group that incorporates members from regulatory bodies, industry, consultancy and academia.
The SuRF-UK framework has received an enthusiastic welcome and is now widely used in the UK and elsewhere in the world. It includes a comprehensive set of supporting guidance including a framework document, indicator categories and suggestions, technical support for establishing sustainability assessment boundaries and parameters, baseline sustainability management practices and carrying out qualitative sustainability assessment (see www.claire.co.uk/surfuk).
This presentation will focus on the use of Sustainability Management Practices (SMPs) to support operations throughout the contaminated land management process from site investigation through to remediation deployment and verification and will demonstrate how National Grid Property have used the SMP concept and established a set of expected standards to help embed sustainability into their land regeneration activities.
SuRF-UK defines SMPs as “relatively simple, common sense actions that can be implemented at any stage in a land contamination management project to improve its environmental, social and/or economic performance”. SMPs can be used to improve the benefits (e.g. resource efficiency, cost) or reduce the negative impacts (e.g. spillages, complaints) of a project, leading to project ‘sustainability gains’, without requiring a formal sustainability assessment (e.g. following a framework such as CL:AIRE, 2010) at site-specific level. SMPs may also be used where sustainability gains are sought at a programme of work level using generic criteria or standards that can apply to a range of project types.
The use of best (or good) practice by the contaminated land sector has been encouraged in the UK for a few decades. This is supported by a robust range of standards, codes of practice and technical guidance published by authoritative bodies from which the SMPs are derived. SMPs are not necessarily “new things to do” in addition to standard practice. They do however offer a way of changing behaviours or actions to reduce the cost, use of natural resources and/or the negative impact on community or the environment.
What is new is that the actions are mapped against the SuRF-UK indicator categories to place even simple and low cost actions in a sustainability context. It is SuRF-UK’s contention that SMPs provide practical and generally inexpensive actions that can yield demonstrable ‘sustainability gains’ for a project. They should be selected where there is a clear benefit in doing so on a project-by-project basis.
A set of headline activities covers generic management activities and also those associated with the main stages for the management of land contamination:
• Procurement
• Land use planning
• Risk assessment (primarily Site Investigation)
• Options Appraisal
• Implementation of remediation – Design
• Implementation of remediation – Construction and Operation
• Implementation of remediation – Verification/Long-term Monitoring and Closure
The SMPs are provided in an Excel spreadsheet file, downloadable from www.claire.co.uk/surfuk. This format means that the SMPs can be readily modified or updated. If modified or updated it is important that the source of information from which a new SMP is derived is cited. A report is also available that describes the development of SMPs and instructions for use of the SMP spreadsheet (CL:AIRE, 2014).
The benefits to a practitioner and client in adopting sustainable approaches to all activities associated with the management of land contamination include:
• Demonstrate compliance with legal or corporate sustainability policies
• Save capital and/or operational costs
• Achieve a reduction in emissions to air, water and land
• Achieve efficient use of energy and natural resources
• Minimise production and disposal of waste, and optimise recycling and re-use
• Achieve or exceed corporate targets
• Support local businesses and contribute to local employment
• Be a “good neighbour”
• Operate transparently
• Minimise plant mobilisations
• Optimise data collection.
References:
CL:AIRE, 2010. A framework for Assessing the Sustainability of Soil and Groundwater Remediation. CL:AIRE, London.
CL:AIRE, 2014. Sustainable Management Practices for Management of Land Contamination. CL:AIRE, London.
Development of a Green Remediation tool for sustainability assessment of soil remediation in Japan
In order to promote sustainable remediation of contaminated sites, we developed a green remediation tool inserted with 16 soil remediation methods. This tool includes 19-100 (?) environmental inventories, and can integrate these inventories into a single index (a monetary value “yen”) using a life cycle impact assessment method based on endpoint modeling (LIME2).
In this study, we used this tool to evaluate remediation of an arsenic-contaminated site. Five remediation methods, were compared: 1) excavation and off-site landfill disposal (EOL), 2) excavation and on-site landfill and washing of contaminated soil (EOW), 3) in situ insolubilization (ISI), 4) in situ containment (ISC), 5) and groundwater monitoring (MN).
Our results showed that the integrated environmental impact associated with the EOL method totaled 1.3 million yen/3000m3, followed by 1.18 million yen/3000m3 for the EOW method, 0.72 million yen/3000m3 for the ISC method, and 0.61 million/3000m3 yen for the ISI method, indicating that in situ remediation is more advantageous, in terms of environmental impact, than off-site remediation. At 0.01 million yen/3000m3, the MN method exhibited the least impact. Based on the damage analysis, all of the remediation methods were associated with markedly higher integrated impacts on human health and social assets than on biodiversity and primary production. In terms of impact category analysis, major impacts associated with each remediation method were global warming, urban area air pollution, and resources consumption. Furthermore, contribution analysis of each remediation process to the total integrated impact revealed that energy consumption contributed markedly to the impact of off-site remediation, whereas the utilization of materials accounted for over 70% of the total impact of in situ remediation. Transport of contaminated soil was a major factor affecting the impact of off-site remediation. The changes of inventories including CO2 emission, PM10 generation and oil combustion were the main contributors to the impact associated with all remediation methods. We believe that these results could serve as an effective reference for remediating heavy metal-contaminated sites or for identifying weaknesses in a particular remediation process.
Within the last decade “sustainable remediation”, i.e. enhancing the “sustainability” of contaminated site remediation by applying the principles of sustainable development has been discussed intensively by different networks and stakeholder groups from different perspectives (SURF networks, NICOLE, Common Forum and others). Among others, the need for appropriate (holistic) assessment frameworks, methods and indicators to compare and rank different remediation options regarding their sustainability has been identified as one commonly accepted outcome of these discussions.
While only a few assessment frameworks have been published so far (e. g. SURF UK), a large variety of “tool-boxes” and “ready-to-use” software packages are in use to identify the most sustainable among different remediation options. As the principle of sustainable development is claiming intra-/intergenerational equity in terms of environmental, economic and social implications, comparing different options regarding their sustainability can be seen as a classical multi-criteria assessment problem. Although the multi-criteria problem is recognised and all three pillars of sustainability are addressed by most of the assessment approaches, there are remarkable methodological differences. Surprisingly, this applies in particular for the assessment of environmental effects.
In our contribution we will give a brief overview on the historical development of sustainable remediation and the main players promoting its implementation into contaminated site management. We will address the theoretical background of assessing sustainability and discuss the suitability of different assessment methods. Special emphasis will be given on the selection of environmental sustainability indicators since identifying appropriate environmental indicators, in our opinion, represent one of the most crucial issues in order to get reliable assessment results. The theoretical discussion will be exemplified by an analysis of recent trends in the assessment of sustainable remediation. Based on contributions to scientific conferences, such as AquaConSoil 2013 or the International Conferences on Sustainable Remediation 2012 and 2014, it can be shown that contrary to secondary environmental effects, which are considered by almost all assessment methods, only a minority of assessment methods are counting for primary environmental effects. Generally, primary environmental effects are linked to the environmental goals of remediation measures (e.g. reducing risks for humans and the environment), whereas secondary environmental effects comprise accompanying side effects (e. g. greenhouse gas emissions, waste generation, water consumption, energy demand), which mostly are unintended. Similar to secondary environmental effects, remediation options may also differ in their ability to meet environmental goals significantly; meeting the remediation targets set by the authority may be seen as a minimum requirement. Thus, neglecting primary environmental effects may result in a biased ranking of remediation options. Other examples for a considerable impact on assessment results are related to the role of holistic assessment frameworks and system boundaries.
In conclusion, an inappropriate selection of sustainability indicators, and in particular counting for secondary environmental effects only, implies the danger of the tail wagging the dog.
In order to improve and support decision-making regarding the selection of remedial techniques for contaminated sites a multi-criteria assessment (MCA) method has been developed. The MCA tool compares the sustainability of remediation alternatives by integrating environmental as well as societal and economic criteria in the assessment. In addition, the method encourages stakeholder participation by including stakeholder-derived criteria weights.
The MCA method was developed using a hierarchical structure and includes five main decision criteria: Remedial effect, remediation cost, remediation time, environmental impacts and societal impacts. Environmental impacts and societal impacts are subdivided into a number of sub criteria. The environmental impacts cover mainly secondary impacts to the environment caused by the remedial activities and are assessed in a life cycle assessment (LCA). The societal impacts are to a large extent local impacts and are mainly assessed in a more qualitative manner on a scale from 1-5. The performance on each main criterion is converted to a score and an overall score is obtained by multiplying each score by a criteria weight.
To illustrate the use of the method it was applied to assess four management scenarios for the Groyne 42 site in Denmark. Groyne 42 is one of the largest contaminated sites in Denmark with an area of 20,000 m2 and is located on the west coast of Jutland. In the 50s and 60s large amounts of waste, mainly residues from pesticide production, was disposed of at the site. In the 70s and 80s, parts of the contamination were excavated, but the deeper contamination was not removed and contains approximately 100 tons of contaminants. In 2006 a sheet pile wall was installed around the contaminated site in order to prevent the transportation of the contaminants to the North Sea.
The Central Denmark Region is responsible for the management of the site and have proposed four different management scenarios: (1) Excavation of the site followed by soil treatment, (2) In situ alkaline hydrolysis, (3) In situ steam enhanced extraction and (4) Continued encapsulation of the site (no removal of contaminants).
The five management scenarios were assessed using the MCA method described above. The various impacts were weighted using a stakeholder panel who assessed the importance of the five main criteria (Effect, Economy, Time, Environment and Society) in relation to each other. The stakeholders gave the highest weighting to the remedial effect of the methods and to the societal impacts.
The developed multi-criteria method provides useful insight into how the remediation scenarios compare to each other in terms of remedial effect, cost, time use and external impacts to environment and society. In addition, it offers a possibility for summing the weighted criteria scores in order to identify which option is more sustainable. For the Groyne 42 case study, the excavation option obtained the lowest overall score in the MCA and was therefore found to be the more sustainable option. This was especially due to the fact that this option could efficiently remove both pesticides and mercury and therefore obtained a high score in Effect, which was given a large weight by stakeholders. The continued encapsulation was found to be less sustainable than the other options. This was partly due to the fact, that this option would not improve the reputation of the area and therefore had large social impacts.
Bacterial communities play a pivotal role in biogeochemical cycle, however there is still no consensus on the effect of pesticide contamination on bacterial community function, especially on their ability to reduce nitrate, which is an issue in several pesticides impacted sites. Atrazine is an herbicide which have been widely used for weed control in corn, soja and sorgho cultures, until 2003 when it has been withdrawn in France. Desethylated atrazine (DEA) is among its metabolite the one most observed in soil and groundwater and it has been reported with higher effect to aquatic life, than ATZ. Ten years after its withdrawn, ATZ and DEA concentrations exceeding the legal EU thresholds for groundwater and drinking waters (0.1 µg/L) are still reported.
Our objective was to assess the effect of pesticide mixtures on groundwater microbial abundance, community structure and their function in the nitrate reduction at the catchment level. This is, to our best knowledge, the first study on pesticide impact on groundwater microbial community diversity structure and function; it has the potential to provide sound-based arguments to be considered when improving the current strategy to manage water quality, as well as when proposing end points to monitor the microbial community in the biodiversity objective under the European water directive framework.
Two-year monitoring. The Ariège alluvial plain (France) is contaminated with a large panel of pesticides with concentations up to the ppm level. Water (1 L) was sampled from 17 selected springs on a monthly basis during 2 years (March 2012- March 2014, n = 50).
Microcosm. Water was sampled in July 2014 in two wells having different contamination profils. Water (700 mL) was placed in 1 L microcosm and ATZ, DEA or ATZ+DEA was spiked at 0, 1 and 10 µg/L. Units were sacrificed at the start and following 15-day and 30-day incubation (n = 58).
Bacterial analyses. Water was filtered through 0.22 µm filters and microbial DNA was extracted. Abundance of the universal marker (16S rRNA gene) and of nitrate-reducing bacteria (narG and napA genes) were assessed by quantitative PCR (qPCR). Diversity was assessed using fingerprinting technic, CE-SSCP (Capillary Electrophoresis-Single Strand Conformational Polymorphism).
Chemical analyses. Water samples for pesticides were analyzed by LC-MS/MS following an on line-solid phase extraction, and samples for anions and cations were analyzed by ion chromatography.
Statistical analyses. Divergence between diversity profiles were analyzed with StatFingerprints software. Diversity indexes were also calculated (richness, Shannon-weaver index, eveness). Statistical differences were analyzed using two-way ANOVA with treatments, chemical or incubation time as factors (p < 0.05). Principal component analyses (PCA) were performed using XLSTAT Version 2011.2.02.
Biodiversity was higher thorough the experiment in the water C+, historically contaminated with various pesticides than in the water C- where none of the 51 pesticides monitored was observed during 2 years (Figure 1). Pesticide concentrations in the water historically contaminated often exceeded the legal EU threshold for groundwater and drinking waters (e.g. 2-year mean: 0.09 ± 0.01 µg ATZ /L, 0.43 ± 0.06 µg DEA /L (n = 23)). On the other side, during microcosm incubation, biodiversity decreased when spiked-chemical concentration increased from 1 to 10 µg/L. In the water C+, no effect of the incubation duration was noticed. In the water C-, biodiversity decreased with the chemical concentration and increased with the incubation duration when exposed to 1 µg/L, while no increase was observed when the community was exposed to 10 µg/L, suggesting that adaptation to pesticides might occur and this process depends on the chemical concentration. In both waters, there was no difference in the ATZ, DEA or ATZ+DEA effect to the microbial diversity. Abundance of bacteria reducing nitrate among the total community drastically decreased during the experiment, but this decrease was also observed in the control unit (p < 0.05). Total biomass was similar in both waters and during the whole experiment (p > 0.05). No biodegradation of ATZ and DEA was observed during the 1-month exposure.
Analyses of the two-year monitoring at an agricultural catchment level are undergoing; preliminary results suggests that biomass is similar in all samples while biodiversity and nitrate-reducing bacteria show important differences between samples.
The undergoing analyses on natural waters monitored during two years at a catchment level will hopefully show boundaries within the complex relationship between biodiversity and chemical concentrations observed in the microcosm, which is positive at the environmental level (between water C- and C+) and negative at the spiked-concentratoin level (between 1 and 10 µg/L).
In the microcosms, ATZ, DEA or ATZ+DEA exhibited similar effect on the microbial community. Comparison at the catchment level of the effect of the 51 monitored pesticides taken individually or summed, on the microbial biodiversity will enable to assess the mixture effect on the microbial community.
Biomass was similar in all conditions (p > 0.05), suggesting that this is not a sensitive endpoint to assess water quality.
Relationship between pesticide contamination and bacterial nitrate-reducing community will be assessed further to consider the risk of nitrate acumulation or of inhibition effect of nitrate on pesticide biodegradation.
Acknowledgement - The authors thank the Water Agency Adour-Garonne (France), the FEDER grants (Europe) and the BRGM for their financial support.
Successful bioremediation of subsurface environments, such as contaminated soil or groundwater, can depend on a good understanding of microbial degradation processes. Taking into account the complexity of interactions that occur between the solid matrix, indigenous microorganisms and pollutants, initial on-site characterization and in situ monitoring of microbial communities over time are essential. One of the major challenges with subsurface systems has been the development of sampling techniques for microbiological investigations. Reliable sampling is highly critical since detection of microbes and/or their expression, and the quantification of genes involved in degradation processes are often used to design and monitor remediation processes. Conventional (active) sampling usually relies on the collection of individual spot samples and may often lead to an underestimation of the abundance and diversity of the community as well as an important variability.
The objective of our work was to develop and optimize tools for reliable on-site passive sampling of microbial communities in non-destructive manner. Different matrices ranging from activated carbon to coarse sand were tested for enrichment of bacterial growth in monitoring wells. Samplers were maintained over 30 days and the microbial communities enriched on the different matrices compared to the communities of the surrounding soil and interstitial water using molecular tools (e.g., Next Generation Sequencing, RISA, Phylogenetic microarrays). Results obtained showed that the amount of biomass and structure of the communities are different on the different matrices tested. Some solid supports seem less adapted than others in order to sample in a reliable manner the microbial communities present in the surrounding water and soil. Therefore, the choice of the matrix selected to passively sample subsurface microbial communities is highly critical and some material are to be avoided. Data obtained with the different matrices in different environments will be presented and the advantages and limitations of such approach for different applications will be discussed.
Title: Microbial responses to biostimulation and bioaugmentation – a 2-year long pilot trial to evaluate molecular sampling techniques
Helena Branzén*, Lennart Larsson, Märta Ländell, Anja Enell
Swedish geotechnical institute, 581 93 Linköping
*speaker, helena.branzen@swedgeo.se +46-709-73 01 13
To evaluate different approaches to sample microbes, a two year-long field study was performed at a site contaminated by chlorinated ethenes. In the study, the outcome of using common groundwater samples was compared to the outcome from two different molecular sampling tools; a sampling tool with an artificial carrier for the collection of microbes over time and a sampling tool containing soil from the site. The pilot test was initiated in 2012, and performed in parallel to the assessment of reductive dechlorination as a potential remediation technique at a dry cleaning site in Alingsås, Sweden.
Background
For a bioremediation project to be successful, reliable methods to predict the degradation potential is crucial. It is important that sampling methods, as well as the molecular analysis carried out, reflect the true degradation potential of the subsurface system. Active microbial populations develop and thrive in environments offering nutrients and substrates necessary for respiration and cell growth. The tendency for microorganisms to attach to sediment particles is well-known, and bacterial density in communities attached to sediment may well be a factor 103 – 104 higher, compared to the density of free-living communities in groundwater. Of practical reasons, molecular analyses to a large extent focus on bacteria collected in the pumped groundwater, i.e. rendering a snapshot of the bacterial density. However, due to the organisms preferences for particles, the absence (or very low densities) of singled out specimens in groundwater may not be conclusive with corresponding absence in soil. To assess the potential for reductive dechlorination, or to subsequently monitor performance during remediation, techniques focusing on attached communities is supposed to offer a more reliable decision basis. Passive sampling tools that collects microbes over time has thus been developed. The Standard BioTrap® consists of a carrier material that mimics soil particles and stimulates colonization of active bacteria. With a larger bacterial density, the registration of background levels and evaluation of steps taken to enhance reductive dechlorination is considered to be more reliable. However, the results generated by this sampling tool does not reflect the soil ”history”, like competing microorganisms or predatory microorganisms (for example those feeding on the dechlorination bacteria). Neither chemical composition, nor structure of the carrier material is identical to that of the soil. Over the years, attempts have been made to use soil mesocosms to even better simulate natural conditions. However, for economical and practical reasons, in-situ mesocosms have not become a common practice in the field. Mesocosms may be described as small perforated containers filled with anaerobic handled soil from the contaminated site. The mesocosms are deployed in the groundwater wells from where they originally were collected and harvested at different stages of the trial.
In this study, we have evaluated the consequences of applying these different sampling techniques (i.e. a) conventional ground water sampling, b) Standard Biotrap® and c) in-situ mesocosms), in relation to the assessment of dechlorination potential, such as choosing remediation technique or assessing the need for additional biostimulation or bioaugmentation. The detection levels and sensitivity for variations in the amount of selected microorganisms and their gene-potential for dechlorination, triggered by biostimulation and and bioaugmentation have been compared. The hypothesis was that analysis of mesocosms, compared to analysis of groundwater and artificial Bio-Trap®, would give a more reliable result for presence of specific microorganisms and better register changes in the microbial composition after biostimulation and bioaugmentation, due to the larger amount of colonizing bacteria.
Aim
The aim of this presentation is to share experiences and conclusions from the pilot trial, performed during 2012-2014. More specific we wish to present /show apparent responses from the different sampling techniques/tools to biostimulation and bioaugmentation by evaluating detection sensitivity and sensitivity to variations in the microbe gene sequences over time.
Results
During the trial period, microbes were collected from three closely situated groundwater wells. All three wells were subjected to biostimulation (molasse and Newman Zone®), while two of the sampling wells were bioaugmented with KB-1® culture and smaller amount of lactate.
• Preliminary results from the trial show higher bacterial density (a factor 102 – 103) in soil mesocosms compared to both groundwater and Bio-Trap®.
• Bacteria dechlorinating PCE and TCE (Dehalobacter restrictus, and Desulfuromonas spp.) were continuously identified by the soil mesocosms, while groundwater and the artificial samplers did not always identify Desulfuromonas spp.
• After bioaugmentation, the groundwater (snapshot) and Bio-Trap® (passive sampler) showed quick responses, measured as Dehalococcoides spp. and gene copies involved in VC and ethene/ethane formation in comparison with the development in the mesocosms. The responses from the soil mesocosms were delayed, and while VC and ethane production declined, the number of gene copies, involved in the formation of VC and ethane, were increasing.
Integrated characterization of the development in natural attenuation of a PCE plume over 7 years after thermal remediation of the source zone with use of dual stable isotope and microbial techniques
Mette M. Broholm1, Alice Badin2, Carsten S. Jacobsen3, Philip Dennis4, Niels Just5, and Daniel Hunkeler2
1Technical University of Denmark, 2University of Neuchatel, 3GEUS, 4SiREM, 5Region of Southern Denmark.
PCE DNAPL contamination at the former central dry cleaning facility in Rødekro, Denmark, was subject to thermal (steam) source zone remediation in late 2006. A > 2 km long plume of chlorinated ethenes (PCE and chlorinated degradation products) which has migrated downgradient from the source zone has not undergone active remediation. A study of the natural degradation within the plume prior to source treatment including stable isotope monitoring was conducted in 2006(-2007) by Hunkeler et al. (2010). This investigation documented complete degradation of PCE via TCE to DCE by reductive dechlorination 1-1.5 km downstream the source area, where the plume descends into more reduced groundwater. It further proved that cDCE was further degraded by reductive dechlorination to VC, and that VC was not accumulated but further degraded, potentially by another pathway (not reductive dechlorination). Detection (< quantification limit) of specific degraders (Dehalococcoides) enforced that cDCE degradation was biotic reductive dechlorination. The understanding of the degradation within the plume, not least the documentation of VC degradation, was essential in the risk evaluation of the plume.
The scope of the new (2014) study is to evaluate how the source remediation has impacted the plume and in particular the natural attenuation within the plume.
The evolution in plume composition and attenuation has been monitored by the Region of Southern Denmark on an annual basis since the remediation, and in 2014 a large monitoring campaign including redox, chlorinated ethenes, non-chlorinated degradation products, carbon and chlorine stable isotope composition, specific degraders and their activity and next generation sequencing (454 pyrotag) for bacterial composition was conducted.
The source remediation has, in addition to direct reduction of the concentration level in and flux from the source area, resulted in the release of dissolved organic matter and some geochemical changes. This has had an effect on redox conditions and biodegradation by reductive dechlorination particularly in the near source area. However, also in the further downstream area of the plume redox and contaminant levels have changed, suggesting an evolution in natural attenuation at significant distance (>1 km downgradient) from the treated source area. Dual isotope analysis are currently being conducted. Dual isotope and microbial data will be processed for interpretation of the changes in redox and degradation processes within the plume.
The understanding of the degradation processes within chlorinated solvent plumes and the effects of source remediation on these is essential for the risk evaluation of the plumes, and it has significant influence on decisions regarding costly plume remediation efforts. This project is unique in the integrated characterization approach for line of evidence evaluation of the natural attenuation of cDCE and VC in the DCE dominated plume and the monitoring of the effects of source remediation on plume natural attenuation.
Reference:
Hunkeler, D., Abe, Y., Jeannottat, S., Westergaard, C., Jacobsen, C.S., Aravena, R., and Bjerg, P.L., (2011). Assessing chlorinated ethene degradation in a large scale contaminant plume by dual carbon-chlorine isotope analysis and quantitative PCR, J. Contam. Hydrol., 119, 69-79.
Polycyclic aromatic hydrocarbons (PAHs) are among the most abundant contaminants in the environment which mostly originate from anthropogenic sources like mineral oil spills or former gas plants. Due to their toxic, mutagenic, and carcinogenic effects to humans and animals, PAHs are pollutants of particular concern, thus the effort to reduce their environmental impact is of paramount importance. Biodegradation of PAHs has been demonstrated in laboratory studies under both oxic and anoxic conditions. However, the role of biodegradation for in situ reduction of PAHs at polluted field sites is only partially understood, in particular due to the limited number of approaches to evaluate the biodegradation of PAHs within contaminated aquifers.
In the present study, the biodegradation of four PAHs (naphthalene, fluorene, phenanthrene, and acenaphthene) was investigated in an oxic aquifer at the site of a former gas plant using a novel integrated approach comprising in situ and laboratory microcosms amended with 13C-labelled PAHs as tracer compounds. In situ microcosms with 13C-labelled substrates (BACTRAP®s) aim to enrich indigenous groundwater microorganisms on site and subsequent analysis of their community structure and carbon assimilation patterns (for review see [1]). BACTRAP®s were amended with either 13C-labelled naphthalene or fluorene and were incubated for a period of over two months in two groundwater wells located at the contaminant source and plume fringe, respectively. Subsequently, the assimilation of 13C-carbon derived from the 13C-labelled PAHs into amino acids extracted from BACTRAP®-grown cells was analysed. Amino acids showed significant 13C-enrichments with 13C-fractions of up to 30.4% for naphthalene and 3.8% for fluorene, thus providing clear evidence for the in situ biodegradation and assimilation of those PAHs at the field site. In contrast to several laboratory microcosm studies, showing potential inhibitory effects of high PAH concentrations or complex contaminant mixtures on PAH biodegradation, microbial degradation of naphthalene and fluorene was observed in situ in both the contaminant source and the plume fringe. Recently, we could identify members of the orders Burkholderiales, Actinomycetales and Rhizobiales as the most active microorganisms in the naphthalene degrading microbial community by analysing 13C-labelled proteins extracted from the BACTRAP®s [2].
In order to provide quantitative information on the PAH biodegradation, a laboratory microcosm study was additionally conducted. Groundwater and BACTRAP®-grown cells were used as inoculum. All laboratory microcosms were incubated under in situ-like conditions, using 13C-labelled naphthalene, fluorene, phenanthrene, and acenaphthene as tracers. Mineralisation of 13C-labelled PAHs was detected with high sensitivity and quantified by analysing the formation of 13C-CO2 [3, 4]. Observed PAH mineralisation rates ranged between 17 mg L-1 d-1 and 1639 mg L-1 d-1. On the basis of our results, we consider Monitored Natural Attenuation (MNA) as a potential management strategy for this field site.
References:
1. Bombach, P., Richnow, H.H., Kästner, M., Fischer, A., 2010. Current approaches for the assessment of in situ biodegradation. Appl. Microbiol. Biot. 86 (3), 839-852.
2. Herbst, F.A., Bahr, A., Duarte, M., Pieper, D.H., Richnow, H.H., von Bergen, M., Seifert, J., Bombach, P., 2013. Elucidation of in situ polycyclic aromatic hydrocarbon degradation by functional metaproteomics (protein-SIP). Proteomics 13 (18-19), 2910-2920.
3. Morasch, B., Höhener, P., Hunkeler, D., 2007. Evidence for in situ degradation of mono-and polyaromatic hydrocarbons in alluvial sediments based on microcosm experiments with C-13-labeled contaminants. Environ. Pollut. 148 (3), 739-748.
4. Nijenhuis, I., Stelzer, N., Kästner, M., Richnow, H.H., 2007. Sensitive detection of anaerobic monochlorobenzene degradation using stable isotope tracers. Environ. Sci. Technol. 41 (11), 3836-3842.
Background
Pesticide pollution of water resources is a widespread global problem. The United Nations Environment Programme note in their fifth Global Environment Outlook report that up to 90% of water and fish samples are found to be contaminated with pesticides, and in a Danish study 99% of the kids participating in the study were found to have pesticide residues in their urine. Especially, pollution of groundwater may be troublesome as these pollutions tend to be long lasting due to the stable biological/physico-chemical environment and long retention time of groundwater. In Denmark, pesticide pollution of groundwater has been monitored carefully since the beginning of the 90s, and here it has been found that close to 50% of the groundwater has been polluted with pesticides. The most commonly used treatment technique, activated carbon, comes with known disadvantages, and furthermore, pesticides found in groundwater are often small and polar, leading to inefficient removal by active carbon. As an alternative we studied the use of the advanced oxidation process (AOP) electrochemical oxidation (EO) and nanofiltration/reverse osmosis (NF/RO) membranes for the treatment of pesticide polluted groundwater.
Experiments and Results
Experiments were conducted with commercially available NF/RO membranes in order to clarify the applicability of these membranes to treat pesticide polluted groundwater. Both laboratory grade and real groundwaters were used to investigate the effect of the groundwater matrix. EO was carried out with two different anode materials, Pt and BDD, and in three different solutions: an inert sulphate electrolyte solution, an electroactive chloride electrolyte solution and a real groundwater solution. In these experiments focus was on the efficiency of the degradation and the formation of by-products. Finally, the membranes and the EO were combined to investigate the effect on the energy efficiency of the EO degradation and the overall energy required to treat polluted groundwater.
The experiments showed that high removals of pesticides in groundwater can be obtained with currently available membranes (95-99%), and that the rejection will increase with increasing ionic strength of the groundwater. However, the smaller and increasingly polar pesticides found in groundwater may require use of RO membranes to obtain sufficiently high rejections. The pollutant BAM was found to be completely removed with both anode materials. Use of the BDD anode resulted in fewer by-products, and could be used to obtain complete mineralisation. When chloride was used as the electrolyte, a more diverse group of by-products were seen, but the total amount of by-products was smaller. Finally, combination with a RO membrane resulted in a more energy efficient EO degradation, and when the whole system energy was determined, it was found that 95% less energy was required compared to using the EO as a stand alone operation.
The Collstrop site, a former wood preservation plant, represents a highly soil contaminated area with contaminants of copper, chromium and arsenic. The contaminants were originally used in the impregnation process. The content of copper, chromium and arsenic (1000-2000 mgCu/kg of soil, 300-600 mgCr/kg of soil and 200-1200 mgAs/kg of soil) are clearly above the Danish clean soil criteria, that are 500 mgCu/kg, 500 mgCr/kg and 20 mgAs/kg. The contaminants are primarily found associated with the fine fraction of the soil (<0.063 mm), where more than 95% m contaminant/m soil can be found (4000-10000 mgCu/kg of fine fraction, 1000-2500 mgCr/kg of fine fraction and 3000-8000 mgAs/kg of fine fraction). The Collstrop site only poses minimal risk to the nearby recipients and the groundwater resource in the area, but it is a standard site for wood preservation. The site is therefore used by The Capital Region of Denmark for testing remediation methods. The objective is that these methods in the future can be applied on similar sites where remediation is required due to risks towards groundwater and recipients.
Removal of ionic contaminants is being performed with help of an electrodialytic remediation (EDI) method. The method is a ex-situ continuous process, where ions are separated from soil slurries with help of applied electric field to electrodes isolated from soil slurries by ion-exchange membranes. Anions, like arsenite and arsenate, are removed to the anode compartment through a anion-exchange membrane and cations, of copper and chromium, are moved into a compartment with cathode through a cation-exchange membrane. Application of the electrodialytic remediation developed at the Danish Technical University has been well described in last decades, but was mostly applied as laboratory and bench scale experiments with very limited mass of treated material (Ottosen & Hansen, 1992). Previous laboratory experiments proved that it is possible to remove Cu from 1360 to 40 mg/kg soil in the part of the soil closest to the anode in 70 days without any enhancement of the system (Ottosen et al. 1997). However As is not removed significantly in this system. This is mainly because the soil is acidified during the remediation, and in acidified soil As will mainly be present in uncharged species (H3AsO3 in case of As(III) and H3AsO4 in case of As(V)). Such uncharged species are not transported in the applied electric field. However increasing pH, to pH=3-4, has significantly increased arsenic species removal, but reaching a removal efficiency of only 60% (Sun et al. 2012). The last and other previous studies have also shown an energy consumption corresponding to between 25 kWh and several thousand kWh per ton of soil at 20% fine fraction. Furthermore the treatment of the finest soil fraction will reduce treated mass and increase initial contaminants content, which is expected to increase the removal efficiency and reduce the process energy consumption to below 200 kWh/ton of soil. Based on previous successful experiences with EDI remediation an upscaling of the process has been proposed to treat 15 tons of contaminated soil according to following on-site procedure:
1. Soil excavation.
2. Separation and soil fractionation in a soil washing facility.
3. Performing on-site EDI remediation on the fine fraction
4. Soil regeneration.
The first results indicates that the two step process, removing first Cr and Cu under strongly acidic conditions and then As under circum-neutral pH, showed that it is possible to remove Cu and Cr within 2 days of the EDI treatment. As expected, more problematic is removal of arsenic that is associated with iron hydroxides. Therefore the main challenge for upscaling is overcoming the issue of arsenic mobilization from the fine fraction with parallel ensuring that arsenic species are in ionized form, as anions, that can be attracted by anode.
The aim of this study is to confirm the feasibility of the EDI remediation and implementation of the proposed procedure for soil treatment. The pilot scale investigations give an opportunity to evaluate the EDI process, find its drawbacks and foremost improve it to developed cost-efficient soil remediation technology.
The project is carried out in collaboration between DTU-Byg at the Technical University of Denmark and Orbicon A/S and a project owner is Center for Regional Development, Capital Region of Denmark. We expect to perform all pilot scale investigations and reporting within spring 2015.
We would like to acknowledge Center for Regional Development, Capital Region of Denmark for funding the project and their support.
References:
Hansen H.K., Ottosen L.M., Kliem B.K., Villumsen A. (1997) Electrodialytic remediation of soils polluted with Cu, Cr, Hg, Pb and Zn. J Chem Technol Biotechnol 70:67–73.
Ottosen, L.M.; Hansen, H.K. (1992) Electrokinetic cleaning of heavy metal polluted soil. Internal report. Fysisk-Kemisk Institut and Institut for Geologi og Geoteknik, Technical university of Denmark.
Sun, T.R., Ottosen, L.M. Jensen, P.E.; Kirkelund, G.M. (2012) Electrodialytic remediation of suspended soil – Comparison of two different soil fractions Journal of Hazardous Materials, vol: 203-204, p. 229-235
STAR is an innovative in situ thermal technology based on the principles of smoldering combustion, where the contaminants are the source of fuel. This presentation provides (1) a summary of how the integration of the conceptual site model (CSM) with regulatory objectives and pilot testing lead to the acceptance and application of the innovative STAR technology as the remedial alternative to treat coal tar-impacted soils at a former industrial facility in Newark, New Jersey; and (2) the full-scale design, and the early results of the full-scale application of the STAR technology.
A CSM was developed utilizing historical data, and a combination of traditional and high resolution characterization methods. Three phases of pilot testing were conducted within two hydrogeologic units at the site (i.e., surficial fill and underlying sand units). These pilot tests were conducted to evaluate key design parameters such as: 1) contaminant mass destruction rates; 2) STAR well radius of influence (ROI); and, 3) vapor emissions levels. These data were integrated into the design of a full-scale STAR treatment system for the site with operations commencing in 2014 and continuing through mid-2016.
The conceptual site model identified zones of impacted volume applicable for STAR treatment. Pilot testing within the surficial fill unit demonstrated sustained destruction rates in excess of 800 kg/day supported through air injection at a single well. Deep sand unit testing (twenty-five feet below the water table) resulted in the treatment of a targeted six-foot layer of impacted fine sands to a radial distance of approximately twelve feet. These results (and additional parameters) were used to develop a full-scale STAR design consisting of approximately 1500 surficial fill ignition points and 500 deep sand ignition points and two treatment systems (air distribution and vapor collection / treatment system) to remediate an approximately 14-acre footprint of contaminated soils within the project timelines (i.e., by mid-2016). The Remedial Action Work Plan is being approved through the LSRP program. Field activities began in early 2014 and progress is currently on-schedule.
Smouldering remediation is capable of removing in excess of 99.9% of hazardous organic liquid contaminants in soils in periods of hours or days. The high temperatures of this process affect soil mineralogy and geochemistry. Highly contaminated sites where smouldering remediation is likely to be deployed tend to have complex contamination issues. For example, former manufactured gas sites tend to have contaminants such as coal tars; potentially toxic elements (PTEs) such as lead, cadmium, chromium, and mercury; spent oxides; and other contaminants of potential concern. The impact of smouldering on the fate of PTE co-contaminants is essential to establish.
Laboratory tests were conducted on a field-obtained soil to determine total and available PTEs. Four variations of this soil were studied: before contamination; after artificial contamination with 0.8g/kg coal tar and remediation by smouldering; before remediation but with artificial contamination by six common PTEs; and after contamination of PTEs and coal tar and remediation by smouldering. Soil pH and organic matter were measured before and after remediation. Total PTE content was determined by acid digestion and analysis by ICP-OAS and cold vapour atomic fluorescence spectrometry. USEPA Method 1313 was used to establish liquid to solid partitioning of PTEs as a function of pH 2-13.
Total and available PTE contents were affected by smouldering and effects varied by constituent. Smouldering removes soil organic matter, changes soil pH, and changes the oxidation states of some PTE co-contaminants. Changes to pH affect PTE availability after smouldering. PTEs that complex with organic matter (e.g. arsenic) change availability with pH after the removal of organic matter during smouldering. Changes to mineralogy affect availability of other PTEs. Detailed knowledge of PTE presence and fate is essential to ensure suitable design of holistic, site-specific remediation strategies.
Contaminants in clays and silts are long-term sources of pollutants to groundwater, requiring costly remediation and monitoring over many decades. Significant advances have been made in the past few years in the area of electrokinetically (EK) enhanced amendment delivery to treat contaminant source areas in low permeability (low K) and highly heterogeneous subsurface materials. EK is an innovative approach that uses electrokinetic mechanisms to promote migration of amendments through clays/silts through electromigration, electroosmosis and/or electrophoresis. EK approaches are not dependent on hydraulic conductivity, and can therefore achieve uniform and rapid distribution of amendments in clays and silts. Amendments can include electron donors (e.g., lactate), electron acceptors (e.g., nitrate), and/or bacteria (e.g., Dehalococcoides, Dehalobacter) for in situ bioremediation (EK-BIO), or oxidants such as permanganate for in situ chemical oxidation (EK-ISCO). A recent novel addition to the EK toolbox is EK-thermally activated persulfate (EK-TAP) which uses the same infrastructure to both deliver persulfate through clays and silts (using DC current), followed by heating of the soils (using AC current, which is the basis for electrical resistance heating), to heat the soils to ~40oC to activate the persulfate and destroy contaminants in situ.
This presentation will discuss how and where each of these EK remediation technologies works, and will present results from multiple field applications, including a large full-scale EK-BIO application at a site in Denmark, a second EK-BIO field application at a United States Navy site in Florida, and several field applications of EK-TAP, EK-ISCO, and EK-ZVI at chlorinated solvent sites in the United States and Canada. The results of these field applications show that EK enhanced amendment delivery can be a cost-effective and sustainable means of accelerating remediation of source areas in low K and heterogeneous materials.
The geochemistry of urban soils and subsoils brings important knowledge for optimizing urban development. However, little work has been done on this subject so far. As part of a partnership with a developer, BRGM has checked the value of a historical approach of industrial activities and land-fillings, coupled with a 3D geological model to predict soil and subsoil pollution problems.
The developed methodology is based on a synthetic cartography of numerous historical data, which are scattered in various holdings and deal with a) the industry b) made (artificial) ground deposits. It also includes an interpretation of the drilling data (logs) to represent the geological structure in 3D, a classification of made grounds with respect to their contamination potential, the location of potential contamination sources on identified industrial sites and a search for potentially associated contaminants. The combination of all these elements allows assessing the pollutant potential of soils and subsoils linked to industrial activities and embankments. In parallel, the results of analyzes from the contamination diagnostics conducted by the consulting firms on behalf of public and private developers were collected and put into a database developed by us. The intersection of these analyzes with the predictions of contamination potential aims at verifying the accuracy of predictions.
The methodology was applied to the Isle of Nantes (France). The results include in particular a 3D model of urban geology, as well as a digital atlas of industrial sites and service activities at the scale of cadastral parcels (1/2000). The latter will integrate the GIS of the city and also allow updating the national BASIAS database. The correlation rate between subsoil analyzes and predictions on potential contaminants, associated with industrial activities and / or made ground materials, was tested on part of the study area. It appears for instance good for Pb, correct but less good for hydrocarbons.
Even if field investigations are required, this work shows the value of taking into account historical data. The tool developed can guide diagnosis, including the choice of contaminants to search and the sampling strategy. It also allows anticipating the management of excavated soil (volumes, treatment, recovery, reuse), and adjusting urban planning.
The knowledge of urban soils and subsoils quality brings decision aid elements to sustainably manage the urban territory. The input history on industrial activities and made ground, combined with an estimation of the potentially associated contaminants, participates in the characterization of soils and subsoils quality. It is a brick to the 3D representation of the geochemistry of urban underground. This approach raises also questions about urban geology, with particular consideration on made grounds and the possibility of detailed modeling.
KEYWORDS: Construction team, Fixed budget, Time pressure, Chemical oxidation, Stimulated anaerobic degradation
ABSTRACT:
Overview
An old decaying industrial site, a bankrupt galvanizing company, old town, dilapidated buildings with asbestos, extremely high concentrations chlorinated ethenes in soil and groundwater, a cocktail of other substances, heterogeneous soil with lots of clay, intersecting liabilities, no dynamics and no money. That is in a nutshell the situation as it was found fifteen years ago. After many discussions, ideas, initiatives, studies and many years of continued last year launched the reorganization and with amazing results.
Preparation phase
Twenty reputable contractors, often accompanied by consulting engineers saw a big challenge in this job. They could sign up through a rigorous pre-qualification. This resulted in the top five forwards. These five contractors were allowed to submit a plan to address how to tackle the problem. One of the main requirements was the budget of 1.5 million Euros.
What can you do for 1.5 million Euro
Under this title NTP Enviro in combination with Bioclear have qualified as the team to come to a final draft for the contaminated site CPC Coevorden. Directly above the core of the contamination with the pure product a number of supermarkets were planned. Development and remediation had to go hand in hand, with different clients and stakeholders within one area.
Based on the remediation targets the conceptual model was updated through additional research. The pure product was present in a much larger area which led to a greater demand for a robust approach. Through lab experiments and feasibility testing, followed by a pilot in an extremely short period of four months, a final clean-up design was drafted based on chemical oxidation and stimulated anaerobic biodegradation. In the presentation we will take you in the process in which despite great pressure of time thoughtful and creative choices were made regarding technique, performance but also the formation of contracts in which one issue was maintained, namely the budget of 1.5 million Euro.
Technology in the service of development
The construction of the underground remediation system was carried out simultaneously with the construction of the supermarket complex. Chemical oxidation using sodium permanganate and stimulated anaerobic biology through the TCE concept (bioaugmentation and anaerobic bioremediation by reductive dechlorination) integrated into one flexible remediation system including a monitoring network designed such that both new construction as well as the in situ remediation could continue. Large quantities of cables and pipes are herein arranged in the soil in a very short time. The available time was under high tension because of the agreements with the developer and the builder of the mall. In the field, it was a maze of contractors and projects simultaneously.
The pressure of time took a lot from all the actors, especially at times of changes, such as the discovery of new spots with pure product. In the presentation, we want to show how the construction phase has taken place and that it is possible also to perform the most robust techniques without compromising developments or infrastructure.
This paper presents the largest In Situ Thermal Desorption (ISTD) project completed to date. The redevelopment of a former aerospace manufacturing facility adjacent to a commercial airport was the main driver, requiring relatively rapid reduction of several chlorinated volatile organic compounds (CVOC) in a 3.2-acre source zone. The source zone was divided into four quadrants with differing treatment depths, heated simultaneously using a total of 907 thermal conduction heater wells. Five different depths were selected across the area, according to the depth of contaminant impact. Prior to implementation, a risk and optimization study led to placement of a vertical sheet-pile wall around the treatment zone to minimize groundwater flow, and a pilot test of a novel direct-drive method for installation of the heater casings. Due to a shallow water table, a layer of clean fill was placed over the treatment zone, and partial dewatering was necessary prior to heating. A network of vertical multi-phase extraction wells and horizontal vapor extraction wells was used to establish hydraulic and pneumatic control and to capture the contaminants. The site was split into four decision units, each with a rigorous soil program which included collecting a total of 270 confirmatory soil samples from locations with the highest pretreatment CVOC concentrations requiring reduction to below 1 mg/kg for each contaminant. Temperature monitoring and mass removal trends were used to trigger the sampling events. Eventually, a small area near the center of the site required the installation of four additional heaters before the soil goals were reached after 238 days of heating. The total energy usage for heating and treating the source area was 23 million kWh – slightly lower than the estimated 26.5 million kWh. Actual energy losses and the energy removal associated with the extracted steam were lower than anticipated. An estimated 13,400 kg (29,800 lbs) of CVOC mass was removed, and all soil goals were met. This paper presents the challenges associated with a project of this scale and describes the solutions to successfully complete the ISTD remedy.
Regeneration and redevelopment of urban brownfields is one of the key measures to prevent urban sprawl as land take being a result of urbanization, is one of the major soil threats in Europe. Urban brownfields are underused areas in the urban structure, which typically envisage difficult subsurface conditions for redevelopment. Soil and groundwater pollution is a common feature which may be a bottleneck for redevelopment of brownfields instead of green fields. The current trend of urbanization increases the importance of careful spatial planning in cities, especially with regard to subsurface conditions. In the remediation sector, there is a broad on-going work to develop methods and tools that supports sustainable remediation. A common idea is that the largest (sustainability) gains are achieved early in projects where they are still flexible, thus incorporating subsurface aspects in the early planning and design phase of a project. This is also valid for urban redevelopment projects. However, in urban projects the responsibilities, tools and knowledge of subsurface engineering and urban planning and design are not integrated. They depend heavily on each other, but work in sectors. The urban designer usually deals with opportunities for socio-economic benefits while the subsoil engineer deals with the technical challenges of the site, in many cases in a late stage. Better cooperation between urban developers and soil specialists can accelerate brownfield redevelopment and potentially identify better and more sustainable redevelopment strategies. The project BALANCE 4P, funded by the SNOWMAN network, provides methods for, and examples of, application of a holistic approach. This approach supports redevelopment of brownfields by integrating technical, economic and social aspects, and provides means for clearly communicating challenges and opportunities of site-specific subsurface qualities. A decision process framework is developed to practically support the knowledge exchange between the two sectors: the framework offers advice on tools and methods suitable for integrating subsurface aspects in early phases of brownfield redevelopment projects. The holistic approach and the decision process framework will be presented and exemplified by three case studies: the Merwevierhaven city-harbour of Rotterdam, the Fixfabriken site in Göteborg, Sweden, and the Alvat site in Buggenhout in Flanders, Belgium. The three sites differ with regard to sub-surface conditions, ownership relations, development visions and governance, and function as examples of integrating urban planning and the subsurface in different settings.
Sustainable Remediation involves the balanced consideration of environmental, social and economic factors in soil and groundwater risk assessment and risk‐management decisions. The principles and practice of Sustainable Remediation are being increasingly promoted and applied to the management of contaminated soil and groundwater in the European Union (EU), including the United Kingdom (UK).
This paper presents the findings of an assessment as to how the actual wordings issued by legislative bodies in the EU and UK can require, promote, or support the application of Sustainable Remediation principles, and how such sections of regulatory text can be drawn upon by contaminated land practitioners and regulatory authorities to develop or support an argument for a sustainable remediation approach.
To fulfil this objective, legislative, regulatory, and technical guidance documents relevant to the contaminated land regime in the EU and UK were subjected to a detailed, systematic review. Specific areas of text identified as both explicitly or implicitly supporting sustainable approaches to remediation were subsequently collated and presented in a format reflecting the phased, risk-based approach to contaminated land management adopted in the UK.
The review found sustainability principles embedded in a wide body of EU directives, and UK legislation, regulation, and technical guidance. These included the Water Framework Directive (2000), the Environmental Liabilities Directive (2004), the Groundwater Directive (2006), the Waste Framework Directive (2008), the Industrial Emissions Directive (2010) and the Priority Substances Directive (2013) as well as the Common Implementation Strategy (CIS) guidance for the WFD and Groundwater Directives.
Some of these principles were over-arching statements that were applicable throughout the project life cycle whereas others were specifically relevant to particular scenarios, that might be encountered at particular stages in progressing from site assessment to remediation: in the UK for example sustainability principles could be brought to bear during the risk assessment process in the setting of the compliance point to protect water resources. In fact, documented regulatory support for sustainable remediation principles encompassed almost all facets of the site assessment and remediation process, including: risk assessment, selection of remedial objectives, remedial options appraisal, and, the implementation of remedial strategies.
Sustainability themes were also strongly represented in sections of key planning policy documents relevant to the contaminated land regime, such as the promotion of brownfield development in urban planning strategies.
The Netherlands was one of the first countries to undertake remediation of contaminated sites. Since the early 1980s, the investigation and remediation of contaminated sites has been high on the agenda, and the recent Midterm Review revealed that the end of the process of managing historically contaminated sites is in sight. The review gave a comprehensive overview of the remaining contaminated sites that need remediation. The objective of the Dutch government is that at the end of 2015 all risks due to soil and groundwater pollution are controlled, and that the remedial programme for historically contaminated sites is reaching the finishing line.
Results Midterm Review
Out of the total amount of contaminated site (estimated on approximately 400.000 sites) only a total of 1539 sites remain that possibly require remedial action. At circa 70% of the sites (1177 sites) the trigger for remediation is the risk of spreading contamination plumes impacting groundwater quality (whereas the risk for humans or ecology near the surface is a priority less than 30% of the sites). A preliminary analysis of the sites where contaminant plumes are spreading in the subsurface indicates that only at 50 sites these plumes are actually leading to a potential risk.
Based on the Dutch soil protection law the Netherlands has almost accomplished the remedial obligations towards historically contaminated sites. This approaching endpoint is made possible by a combination of policy renewal and technical developments. Anno 2015 the Dutch soil protection law is risk based, and the thought of cost-effectiveness of remedial activities is firmly embedded. In addition, monitoring of spreading groundwater plumes is regarded not necessary for the greater part of the contaminated aquifers.
However, compliance to legislation is only one aspect that has to be taken into account. Liabilities are another driver for soil remediation, also for sites were from a legislative context no remediation is necessary. For years it seemed to be lucrative to postpone (additional) soil investigation and remedial activities. But recent jurisprudence in The Netherlands pointed out that registration of a potentially spreading groundwater contamination by the authorities can be a strategic step in controlling liabilities.
During this suggested presentation light will be thrown at the Dutch pragmatic approach, and the impact will be illustrated using several cases and examples:
• Cases that give an impression of the wingspan of the Dutch risk-based approach. E.g. several 10s of tonnes of chlorinated hydrocarbons (including DNAPL) in aquifers can be accepted, as they don’t migrate towards a drinking water station or other vulnerable object. Same accounts for substantial amounts of LNAPL. Regional groundwater management.
• Recent jurisprudence on liabilities concerning site-crossing groundwater plumes
• Compliance of Dutch soil protection law with EU legislation
Green Management and Ecosystem Services of Former Industrial Decantation Ponds
Hermine Huot1,2,3,4, Patrick Charbonnier4, Marie-Odile Simonnot2,3, Jean Louis Morel1,2
1Université de Lorraine, Laboratoire Sols et Environnement, UMR 1120, Vandoeuvre-lès-Nancy, F-54518, France
2INRA, Laboratoire Sols et Environnement, UMR 1120, Vandoeuvre-lès-Nancy, F-54518, France
cUniversité de Lorraine, Laboratoire Réactions et Génie des Procédés, UMR 7274, Nancy, F-54001, France
3CNRS, Laboratoire Réactions et Génie des Procédés, UMR 7274, Nancy, F-54001, France
4Environment & Development, ArcelorMittal Corporate Real Estate, L-1160 Luxembourg
The steelmaking process generates numerous metal-rich by-products. Black furnace sludge were often disposed of in settling ponds, which now require special attention regarding the risks they generate for environmental bodies and human health as a result of their high concentration of metals (e.g. Pb, Zn). After closure and termination of sludge deposits, a vegetation cover may develop, which raises the question of the sustainability of this mode of management analogous to a natural attenuation.
In this context, a former industrial decantation pond closed in the 1950’s, and covered with an alluvial deciduous forest, was characterized i) to assess the risk of transfer of metals to groundwater and organisms and ii) to study the potential influence of vegetation, and in particular roots, on the mobilization of metals. A thorough characterization of the soil developed on the deposits along with lysimeter experiments were conducted. Results showed that a significant range of soluble compounds (sulfates, carbonates) may be released in water, but that metal flow is rather negligible due to low soil permeability and low metal solubility. Also, the presence of vegetation reduces water flow and limits the risk of transfer to groundwater. In contrast, in the rhizosphere soil, extractability of metals may increase as a result of root activity suggesting a potential mobilization of metals in the long term. In conclusion, risk of transfer of metals to groundwater and organisms is limited because of the presence low solubility of metal compounds and of specific physical properties of the sludge materials, which are in favor metal retention. In terms of site management, the presence of a dense vegetation cover prevents dust hazard, stabilizes materials and limits water flow and thus risk of transfer to groundwater. Changes caused by roots on the chemical status of metals are limited in space, but must be monitored to support to this management option.
[1] Huot, H. (2013). Formation, fonctionnement et évolution d'un Technosol sur des boues sidérurgiques, Thèse de doctorat, Université de Lorraine, France.
[2] Huot H., Simonnot M.O., Marion P., Yvon J., De Donato P., Morel J.L. (2013). Characteristics and potential pedogenetic processes of a Technosol developing on iron industry deposits, Journal of Soils and Sediments, 13(3):555-568, doi 10.1007/s11368-012-0513-1
[3] Huot H., Simonnot M.O., Watteau F., Marion P., Yvon J., De Donato P., Morel J.L. (2013). Early transformation and transfer processes in a Technosol developing on iron industry deposits, European Journal of Soil Science, doi: 10.1111/ejss.12106.
In redevelopment projects, much can be gained when the presence of soil contamination is taken into account as early as possible. Not only on the financial side, but also socially and environmentally. The integration of soil remediation in spatial planning and redevelopment is an important aspect of sustainable remediation.
OVAM, the Flemish authority responsible for the management of soil contamination and management of materials and waste, promotes green and sustainable remediation. These days, the integration of sustainable remediation in other processes and policies is emphasized. This will be explained at the hand of two action lines (1) the development of a decision framework and tool for sustainable redevelopment and remediation of sites, and (2) integration of soil remediation in the new policy on spatial planning in Flanders.
Early this year, a workshop on sustainable remediation was held with all stakeholders, such as developers, soil experts, contractors, representatives of industrial sectors, … One conclusion of the workshop was that there is a need for an objective and transparent framework to evaluate sustainability. A framework that allows assessment of sustainability in the different phases of a redevelopment and remediation process: thus also at an early stage, when results of detailed surveys are not yet available. Also, different regulations and policies in Flanders should be taken into account, on soil remediation, but also e.g. on the sustainable management of materials.
Thus, a project was started to develop a 'OVAM sustainability barometer'. The aim is to develop a flexible, web-based and easy to use tool, that can be applied on a voluntary basis. Existing tools will be integrated in this new instrument, e.g. the mullticriteria analysis used for the BATNEEC-evaluation of soil remediation projects. For cases were construction of buildings are involved, the tool will allow the evaluation of sustainable use of materials. The evaluation of 'residual' contamination will be part of the framework. 'Residual' contamination of soil and groundwater causes no risks with the present use of the land. But when the land use changes, human health and other risks may occur.
The project was commissioned to Witteveen+Bos nv. Different stakeholders will be involved during the project. A lot of emphasis is put on visualization and flexibility. The tool will also be used for evaluations of proposals given for sites OVAM wants to sell in the framework of the 'protocol for curators'. These sites were bought by OVAM for one symbolic euro, because no one else was interested to buy it due to high remediation costs.
The second line of action is the integration of soil remediation in the new policy on spatial planning. Recently a 'green paper' on the spatial planning for Flanders in 2050 was published. The paper describes the desired spatial planning and structure for the future, which involves an important change from how it is done now. Poly-centric urban regions, where proximity and accessibility are the guiding principles, are planned together with a vital countryside, where open space is protected. These areas will be connected by networks of blue-green corridors, and measures will be taken to make space more resilient.
In order to achieve this vision, many actions are needed. We need to reduce the intake of green fields, e.g. by brownfield redevelopment. Co-operations with investors will be more important. We have to invent instruments to stimulate investors in a way that the results the society desires are obtained.
Some strategic areas were chosen to first try out this new ideas. One of them is the area North of Brussels, which is an area with many challenges from a demographic, economically and environmental point of view. For smaller zones in this strategic area more concrete plans are drawn up in an interactive way. Strategic visions are produced on different themes, such as mobility, social and demographic aspects, sustainable soil management and sustainable use of materials, …
OVAM is member of the executive committee of this pilot project, together with the administration on Spatial Planning, Brussels Capital Region and the Province of Vlaams-Brabant. This creates the opportunity to make sure soil contamination is taken into account by spatial planning from the very beginning.
Concrete examples to illustrate the current policy will be presented.
The management of contaminated land has moved through different stages over the last few decades, each stage being characterized by a specific approach. The most recent stage is that of sustainable remediation, whereby decisions on the management of contaminated sites have to be sustainable across all the three pillars of sustainable development (environmental, economic and social). In particular, ensuring the social acceptability and support of remediation strategies and actions is currently regarded as being of high importance. The proposed research project aims to improve the development and assessment of sustainability in contaminated land management processes, through the development of an interdisciplinary framework for the integration of new social sustainability indicators with existing indicators of environmental and economic sustainability applicable to remediation projects. The development of this framework requires first the integration of expert and stakeholder-based assessments of social sustainability and the subsequent integration of the social assessments with environmental and economic indicators of sustainability. To achieve these ends, the project advances an original interdisciplinary approach that draws on social network analysis (from sociology), project ecologies (from economic geography) and multi-criteria decision analysis and sustainable remediation (from environmental science). The results are relevant for researchers interested in sustainable remediation, to policy makers, experts and consultants involved in contaminated site management as well as for site owners, local authorities, site neighbors and the interested public.
Background
It is often challenging to remove all contamination sources when dealing with heavily contaminated sites.
On a metal-treating plant in Kvistgaard that lies within an area of special drinking water interest four hot-spot areas with TCE contamination have been found. The majority of the contaminant mass is located in till in both the vadose zone and the saturated zone. A smaller part of the TCE-mass has been found in the underlying saturated sandy aquifer, which may be in hydraulic contact with the primary groundwater aquifer in the area. Risk assessments based on the investigations carried out on the site show that the contamination poses a risk towards the groundwater resource and, in the long run, a risk for the nearest abstraction wells.
A strategy for remedial actions has been proposed focusing on the following three areas; tilly vadose zone, tilly saturated zone and sandy saturated zone (see the figure below). In connection with evaluation of appropriate and suitable remedial methods, the risk assessment has been expanded with the purpose of establishing cleanup levels, which are expected to give the desired environmental effect.
Objective
The objective of the talk is to give an example of a specific risk assessment used to optimize a remedial strategy towards removal of chlorinated solvents. Furthermore the risk assessment is used to evaluate the necessary scope of remediation and the consequences if it is not possible to remove all the contamination, i.e. to illustrate the environmental benefits when using different cleanup levels at each of the four hot-spots. Uncertainties in the risk model, in the selected points of compliance and end-point concentrations and the effect hereof on the resulting risk assessment and choice of remedial action will be discussed.
Content and results
The risk assessment uses back-calculations for each of the four hot-spots to assess 1) the total flux of TCE that is acceptable in the nearest abstraction wells and 2) the flux of TCE that is acceptable in different points of compliance downstream the contaminated site. The calculations take into account that there are more contaminated sites in the area and that the current site therefore is not the only source of TCE contamination of the aquifer. The risk calculations are carried out with Risc5 and DTUV1D.
The relation between source concentrations and the concentration in one or more downstream points of compliance, f.ex. the nearest abstraction well, is described with the aim of assessing the extent of cleanup, cleanup levels and the resulting remedial effect.
The calculation and risk assessment show that the Danish Groundwater Quality Criteria cannot be complied with 100 m downstream the site even though the source areas are cleaned up. Calculated end-point concentrations in points of compliance further downstream in relation to different remedial methods are compared with the overall environmental effects and remedial costs. On this basis the risk assessment makes it possible to select the most suitable combination of remedial methods in order to protect future drinking water interests.
Sellafield is the UK facility for Nuclear Fuel Reprocessing and Waste Management. It is a compact coastal site with an area of around 3 km². It is currently operational and is expected to remain licensed until 2120.
Radioactive material has entered the sub-surface environment during operations following accidental leaks. This material is currently under active risk management prior to a final hazard reduction and remediation phase. Sellafield Ltd is to understand and control the legacy of ground contamination to ensure protection of the workforce, the public and the environment. The main control exercised over this material is through an extensive monitoring and risk modelling programme. This work generates a quantity of important environmental data gathered at public cost. Sellafield Ltd wish to ensure that the best use is being made of appropriate methods for the sampling and analysis of these data.
Soils and groundwater data are necessarily spatially correlated and require dedicated geostatistics data processing. Different spatial anisotropies are observed in the saturated and non-saturated zones and integrated in the model. Uncertainty quantification of contaminated volume estimates according to several radiological waste thresholds is addressed to improve risk analysis (remediation feasibility, costs, waste management…). Finally, a critical review of the sampling effort identifies under- or over-sampled areas based on the spatial auto-correlation description.
Limited exposure from desorption-resistant PAHs in soot and soils
Philipp Mayer1, Varvara Gouliarmou2, Mette Algreen1, Andreas Loibner3, Chris D. Collins4, Ulrich Gosewinkel Karlson2, Kyle James5, Rachel E. Peters5, Steven D. Siciliano5, Stefan Trapp1
1 Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
2 Department of Environmental Science, Aarhus University, Roskilde, Denmark
3 Department for Agrobiotechnology, University of Natural Resources and Life Sciences Vienna, Tulln, Austria
4 Soil Research Center, Reading University, RG6 6DW, UK.
5 Department of Soil Science, University of Saskatchewan, Saskatchewan, Saskatoon, CANADA
Urban soils are generally diffusely contaminated with polycyclic aromatic hydrocarbons (PAHs) by atmospheric deposition of pyrogenic particles such as soot. Additionally at highly polluted sites, much of the PAHs are strongly bound to the soil matrix. Sorption is in both cases the governing process for many exposure and fate processes, which renders total PAH concentrations insufficient for risk assessment and management1. This asks for the implementation of the availability concept in risk assessment and management of contaminated sites, which requires addressing the underlying assumption that desorption-resistant contaminants in solid matrices give rise to limited exposure. Within the Danish REMTEC project, wood soot was incubated in contaminant traps2 for more than one year to remove the readily desorbing polycyclic aromatic hydrocarbons (PAHs) and to isolate desorption resistant PAHs. Four approaches were then applied to rigorously characterize the exposure originating from the desorption-resistant PAHs in the soot, which in some cases was compared to the PAH exposure in agricultural and industrially polluted soils:
(1) Bioaccessibility. Commonly used bioaccessibility extraction methods have insufficient sink capacity for bioaccessibility measurements of PAHs from soot and soils3. Therefore, a new sorptive physiologically based bioaccessibility extraction method had to be developed4,5 and was then applied to determine accessible PAH fractions, which were 1-2 orders of magnitude lower in the treated compared to the untreated soot.
(2) Chemical Activity. Equilibrium sampling was applied to measure chemical activity and freely dissolved concentrations of PAHs6, which were 1-3 orders of magnitude lower in the treated compared to the untreated soot.
(3) Oral uptake. Ιn vivo swine experiments were conducted to determine the systemic uptake after oral administration. Pyrene systemic uptake was 1.3% in the untreated compared to 0.6% in the treated soot, while the respective systemic uptake of benzo(b+k)fluoranthene was 0.9% and 0.4%.
(4) Plant uptake. Plant uptake experiments with radish and diffusive flux experiments using as PDMS passive sampler, were conducted in soils with and without soot addition. The soils used were an agricultural and industrially polluted soil. Concentrations were higher in root than stalk of the plants, and both were rather similar between all soil treatments despite large differences in PAH content and exposure parameters.
Overall, the conducted research supported that desorption-resistant PAHs give rise to limited exposure. Although soot and other pyrogenic materials can contain high concentrations of PAHs, desorption resistance and high KD values will often strongly reduce the actual exposure and risk. Relevant and reliable analytical methods and well defined availability parameters are thus needed to characterize and quantify the actual exposure potentials of a contaminated site, which generally will be elaborated by the combination of readily desorbing and desorption resistant PAH fractions.
Acknowledgements. This research was mainly funded by the Danish Council for Strategic Research through the project “Innovative Remediation and Assessment Technologies for Contaminated Soil and Groundwater (REMTEC)”, and we acknowledge additional support from the European Commission through the project MODELPROBE and the European Regional Development Fund (EFRE) and the Government of Lower Austria (project MACATA, WST3-T-95/017-2012).
References
1 Reichenberg F, Gosewinkel Karlson U, Gustafsson Ö, Long SM, Pritchard PH and P Mayer. 2010. Low accessibility and chemical activity of PAHs restrict bioremediation and risk of exposure in a manufactured gas plant site soil. Environmental Pollution 158: 1214 – 1220.
2 Mayer P, Olsen JL, Gouliarmou V, Hasinger M, Kendler R and AP Loibner. 2011. A contaminant trap as a tool for isolating and measuring the desorption resistant fraction of soil pollutants. Environmental Science and Technology 45: 2932–2937.
3 Collins CD, Mosquera-Vazquez M, Mayer P and Gouliarmou V. 2013. Is there sufficient ‘sink’ in current bioaccessibility determinations of organic pollutants in soils? Environmental Pollution 181: 128-132.
4 Gouliarmou V and P Mayer. 2012. Sorptive Bioaccessibility Extraction (SBE) of Soils: Combining a Mobilization Medium with an Absorption Sink. Environmental Science and Technology 46: 10682–10689.
5 Gouliarmou V, Collins CD, Christiansen E and P Mayer. 2013. Sorptive Physiologically Based Extraction of Contaminated Solid Matrices: Incorporating Silicone Rod As Absorption Sink for Hydrophobic Organic Contaminants. Environmental Science and Technology 47: 941-948.
6 Reichenberg F, Smedes F, Jönsson JÅ and P Mayer. 2008. Vials with polymer coatings of multiple thicknesses for equilibrium sampling of hydrophobic organic compounds in soil. Chemistry Central Journal 2008, 2:8.
Antimicrobial resistance is a growing public health concern in European hospitals and communities. Escherichia coli is one of the most common agents of bacterial infection which causes urinary tract infections as well as more serious infections. E. coli resistance to major antibiotics classes is increasing worldwide.
The aim of the project is to investigate the prevalence of extended-spectrum beta-lactamase (ESBL) producing E. coli in waste water treatment plants in the Burgundy region and to monitor the impact of treated effluents and sludge on water quality in the Ouche watershed near Dijon (East-central part of France). CTX-M is a recently occurring ESBL, encoded by the blaCTX-M genes, which causes resistance to 3rd generation cephalosporins (3GC).
A regional strategy for sampling surface and ground waters will be carried out in relation to existing data, in order to evaluate the capacity of CTX-M producing E. coli to spread and survive in water resources.
Based on previous data on E coli occurrences, we carried out sampling campaign through the studied watershed in order to evaluate the presence of E. coli and CTX-M producing E. coli in groundwater, surface water and springs. We also used molecular methods to monitor the presence of the blaCTX-M genes.
To characterize the dissemination of ESBL producing E. coli in the aquatic system, we have selected several sampling points according to hydrogeological contexts, land use and waste water plants with a particular interest for karst aquifers that are predominant in the studied area. Karst aquifers constitute an important volume of water resources but they are highly vulnerable to pollution even fecal coliform. In soils and aquifer, fecal coliforms are known to suffer retardation and degradation by sorption and filtering and die off. However, where by-pass occurs by preferential (fast) pathways (cracks, fissures and conduits) none of the retardation and degradation processes is effective.
For each sampling point, we combined microbial and chemical approaches.
Cultural detection of E. coli and ESBL producing E. coli was done by plating of selective TBX medium alone or supplemented with cefotaxime (3GC). Cefotaxim resistant isolates were then characterized by antibiotic susceptibility tests and MLST fingerprinting. blaCTX-M genes were monitored by real type PCR following DNA extraction.
Chemical analyses on inorganic elements (Major, trace elements) were performed to characterize the water composition as a tool to understand the water fluxes able to mobilize E. coli and identify the source of ESBL producing E. coli. Knowledge on water composition contributes to characterize hydrogeological features (rock type, time of contact…) mainly by understanding water-rock interactions of the studied system. Water composition allow to define chemical types of waters and anthropic pressure on water using chemical tracers such as agriculture pressure (NO3) or waste water (Boron). These classical parameters have been completed by analyses of REE among them Gadolinium. For tracing the different inputs of pharmaceutical products (that are related to antibiotic resistances) to groundwaters, several specific chemical markers are simultaneously monitored: Gadolinium, caffeine, carbamazepine, ibuprofen and acetaminophen. Positive Gd anomaly has been produced by the application of multidentate organic complexes of Gd in hospitals and clinics, as a contrast medium in magnetic resonance imaging (MRI) since 1988. From a hydro-geological point of view the anomalous Gd represents an excellent tool to trace the mixing of recycled water with surface and groundwater.
From the presence or absence of ESBL producing E. coli we attempt to identify the sources and vectors of water contamination by studying waste water treatment, land use (sewage sludge) and water fluxes in the studied watershed. The occurrence of CTX-M producing E. coli in groundwater resources and particularly the persistence of antibiotic resistance genes (ARG) such as blaCTX-M might constitute a health risk.
The LQM/CIEH S4ULs published in December 2014 are the third edition of generic assessment criteria published since 2006. The 1st and 2nd editions of the LQM/CIEH Generic Assessment Criteria rapidly gained widespread acceptance among practitioners and regulators. In 2012, the 2nd edition was specifically recognised within statutory guidance issues by the Secretary of State to support the contaminated land regime in England and in Wales. The S4UL are published alongside a set of collated information on the toxicity and transport properties for some 85 common contaminants to inform site-specific generic quantitative risk assessment (GQRA).
Although the terms ‘generic assessment criteria’ or ‘GAC’ were often used as synonyms for the 2nd edition LQM/CIEH GAC, these generic terms are also applicable to soil screening thresholds derived by a number of other companies and organisations. Furthermore, the ‘new’ LQM/CIEH S4ULs introduce a number of changes in relation to the modelling assumptions used, and include values for more land uses and substances. Consequently, it was considered appropriate to use a new, individual and specific name for the new criteria – the LQM/CIEH Suitable 4 Use Levels (S4ULs) - to differentiate them from other sets of assessment criteria and indicate their role under the planning regime.
The publication of the S4UL comes at a time when the future direction of government guidance on human health risk assessment of contaminated soils in the UK is being reviewed by Government. In March 2014, Defra published Category 4 Screening Levels (C4SLs) for six contaminants. These are based on a unique toxicological benchmark, the ‘low level of toxicological concern’ (LLTC) rather than the ‘minimal or tolerable level of risk’ basis for the Health Criteria Values defined in SR2 (Environment Agency, 2009a) and which underpin all previous Environment Agency Soil Guideline Values (SGVs) and other GACs. This is because the C4SLs were primarily intended for use under Part 2A of the Environmental Protection Act 1990 to quickly screen out Category 4 sites, where there is “no risk or that the level of risk posed is low”. There has been considerable, and inconclusive, debate amongst contaminated land practitioners and regulators about the applicability, and wisdom, of applying the lower standard of protection represented by the C4SLs, underlain by the less cautious LLTCs, outside of the Part 2A context for which they were derived. For example, under the planning regime sites need to be shown to be “safe” and “suitable for use”. We believe that the use of the current six C4SLs under planning requires an informed decision and site-specific justification by landowners, developers and their advisors to ensure that that the development meets the requirements in the National Planning policy Framework in England and its equivalents in the devolved administrations.
However, we also believe that ongoing safe development in the UK requires an up-to-date set of generic assessment criteria covering a wide-range of the contaminants commonly encountered during the redevelopment of previously developed land, and that are appropriate for the low soil organic matter contents often present in such soils. As such the S4UL remain based on the principles of ‘minimal’ or ‘tolerable’ risk enshrined in current Environment Agency guidance. Thus, the S4ULs are equivalent to the SGVs and previous editions of the LQM/CIEH GAC and hence are relevant ‘suitable 4 use levels’ for use in generic quantitative risk assessments under both the planning and Part 2A regimes.
Smouldering and thermal remediation processes are capable of achieving significant hydrocarbon contaminant mass reductions in soils over relatively short periods of time. Smouldering exposes soils in the treatment zone to temperatures on the order of 600-1100°C for periods of hours to days. Temperature and exposure duration are related to the contaminant type, extent of contamination, soil type, and other site-specific characteristics as well as remediation design parameters. Thermal remediation exposes soils to temperatures of ambient to 750°C for periods of weeks to months. Exposure temperature links to the type of heating used, proximity to heating source, and other design parameters while exposure duration is a consequence of remediation progress and operational decisions. For sites where substantial contaminant mass removal has been achieved, redevelopment including the installation of new infrastructure is possible; however, the effects of high temperature remediation on soil condition are not well understood. Hydrocarbon contamination is known to reduce soil strength. The extent to which soil strength may recover after remediation is unknown. This research explores the effects of high temperatures and associated physical changes on soil strength and geostructure stability after high temperature remediation so that safe redevelopment of formerly contaminated sites will be possible.
This study used sand and a mixture of 90% sand and 10% kaolin as simple soils. Soil samples were subjected to temperature treatments of 105°C, 250°C, 500°C, 750°C, or 1000°C in a furnace to capture the range of exposure conditions encountered during thermal remediation. Subsequent samples were artificially contaminated with 70,000mg/kg coal tar and subjected to smouldering remediation in a 3L vessel in a laboratory setting. An additional sample from a 3m3 smouldering experiment was tested to explore the effects of increased remediation scale and exposure duration. Changes to soil particle size distribution, porosity, surface mineralogy, and other characteristics were determined and compared to the characteristics of untreated soils.
Soil strength was evaluated with a 10cm x 10cm shear box testing using 400g specimens. Soil specimens were delivered to the shear box with aid of a pluviator. Once the specimen was in place, a loading plate was used to establish a vertical stress on the material. The shearing rate was fixed at 0.05mm/s. Vertical stresses of 50, 100, and 150kPa were tested. Subsamples of prepared materials were subjected to cement stabilisation, cured for 28 days, and tested for strength using a triaxial test in order to evaluate their suitability for a typical geotechnical stabilisation technique.
Soil physical properties were affected by heat treatment with changes apparent in particle size distribution, surface mineralogy and other characteristics. Differences were apparent between the sand and sand/kaolin mixture. Some properties such as particle size distribution were not determined for the smouldered samples because of the transfer steps led to particulate losses.
Soil strength linked to exposure temperature with decreases in calculated friction angle noted in the sand. These differences likely associate with mineral changes and potential smoothing of the grains. Kaolin experienced mineral transformation to meta-kaolin and mullite as well as thermal degradation, but these transformations seemed to have the effect of insulating the sand from heat exposure and filling the gaps between the grains. Where decreases in calculated friction angle were noted in the sand-only specimens, increases in calculated friction angle with increasing exposure temperature were observed in the sand/kaolin mixtures. The exception to this trend was the smouldered specimen. Cohesion was variable for all specimens but the smouldered seemed to be slightly less than the heat-treated specimens. Subsequent chemical analysis showed some hydrocarbon contamination remained and this factor combined with handling losses of fines during transfer of material to the shear box may explain the differences.
Post-remediation materials subjected to cement stabilisation were faster to cure and stronger based on triaxial testing. Although the calculated friction angle results reflect slightly lower strength in the field, the same factors that contribute to the lower strength may be benefits in terms of cement stabilisation. The clays interact less with the water and behave more as very fine sands, meaning that the water is taken up faster by the cement and curing starts faster. These preliminary results are promising for field applications of cement stabilisation after remediation, though further tests are necessary to evaluate the full complexity of field geotechnical stabilisation.
Based on these results, field practitioners need to be aware that these high temperature processes may affect soil properties. Site investigation after remediation should be used to establish the geotechnical properties of the post-remediation soil as neither unaffected soil nor pre-remediation contaminated soil will accurately reflect ground conditions. Based on preliminary tests, if soils require stabilisation measures, post-remediation soils seem amenable to one common soil stabilisation technique. Further testing is underway to explore more complex soils and other possible stabilisation techniques.
Expert centre PFCs: Adressing the problem of emerging contaminants
With an increasing frequency chemicals that have not historically been considered as “contaminants” are present in the environment on a global scale. Some of these substances could be a potential risk to humans and the environment and others are harmless. How do we determine the difference and how do we cooperate with stakeholders to address this issue?
Typical examples of these emerging contaminants are PFOS and PFOA (PFCs). Both are applied on a large scale, and both might cause a significant environmental problem. But characteristic for emerging contaminants is that too little is known about the occurrence, the actual risks and approach to formulate appropriate standards and legislation. To properly identify how to deal with PFCs and related emerging contaminants, knowledge, awareness and understanding is necessary.
Although much research on emerging contaminants as PFOS/PFOA/PFCs has been done, information and results are often not accessible outside the academic world. Because of a lack of information, decisions on how to deal with these substances are delayed, legislation is missing and practical solutions are not developed.
In the Netherlands, we therefore started an ‘Expert centre PFCs’ to connect the fields of policy and legislation, science, stakeholders and problem owners and business communities. PFOS is seen as a pilot to come to an approach on how to deal with emerging contaminants, including hormones, medicines, etc.
By making use of the case PFCs, the following challenges are explored:
- which decisions about emerging contaminants have to be made at different levels (production, business, research, polity and legislation);
- which information about emerging contaminants is essential to make these decisions;
- how to ensure that scientific information about emerging contaminants is used in practice, and that people act accordingly. And the other way around: how can practice address important issues and examples to science.
Goal of the Expert centre is to create a ‘ playing field’, in which policy makers in different countries can use the same information about emerging contaminants to base their policy on and explore cost effective and sustainable strategies to deal with these issues.
Keywords: PFCs, emerging contaminants, risk assessment and management
Background / Introduction
Damhusdalen is a residential areaestablished in the 1920s. During development, the land surface was leveled with waste products from porcelain factories among others. The dumping has contaminated the area with hydrocarbons, tar compounds and heavy metals.
In 2004, the Capital Region of Denmark investigated all the properties in the areawith a limited amount of soil samples. The sampling strategy included one borehole per property to determine the thickness of the fill layer and analysis of one soil sample from 0-0.1 and one sample from 0.4-0.5 m. bgs.
The investigations indicated contamination with tar compounds, heavy metals and oil products over at concentrations exceeding DanishMCLs. The top soil (0-0.5 m.bgs) on 150 properties was contaminated. A total of 176 properties out of 180 were identified as contaminated based on the fact that the deeper fill (>0.5 m.bgs) was likely to be contaminated compared to the contamination levels found in the first half meter. Subsequently, the upper 0.5 meters of soil fill were studied with a greater sampling density.
In 2010-2012 the Region studied the results from all the investigations in the area, to obtain an overall representation of the contamination. Based on these studies, the region decided that it was necessary to examine the contamination throughout the whole fill layer, in order to assess whether some properties were in fact uncontaminated.
New studies
The Capital Region performed additional investigations on a total of 42 properties. The purpose of the studies was to gain
• knowledge about the thickness of the fill layer on the examined properties and
• information on the contamination profile throughout the fill.
Based on the results of the new investigations, a statistical evaluation of the level of contamination in the fill soil in the whole area was performed. The primary objective was to investigate whether it was possible to assess the level of contamination in the fill soil deeper than 0.5 meters based on knowledge of the contamination levels in the upper 0.5 m of soil.
The data set consisted of 10.246 analyses in 31 different depths of 229 boreholes spread over 42 properties.
Statistical evaluation
The average analysis for the whole area
Based on the contamination levels in the boreholes, the probability of finding contamination in the fill soil below 0.5 meters, when the fill soil above 0.5 m is uncontaminated, is 10%.
In 13% of all the boreholes, the fill soil was contaminated at depths exceeding 0.5 m. In 31% of those, the fill soil above 0.5 m was also contaminated. Based on this, 24 % of boreholes with contamination in the upper 0.5 meters were also contaminated at depths greater than 0.5 meters.
I.e. to assume that the soil below 0.5 m. bgs is either contaminated or uncontaminated based on findings in the upper 0.5 meters, will include a risk of mapping uncontaminated soil in 75% of the cases and not mapping contaminated soil in 10% of the cases.
Geostatistical view of the area
From a geographical perspective, it is assessed whether it is possible to draw relevant correlations between the individual boreholes based on the compounds and the contamination levels found above and below 0.5 meters bgs.
A view of the substances individually shows that PAHs and heavy metals have a clear geographical correlation between the boreholes at a distance up to 40-60 meters - some with geographic correlation of up to 100 m in fill soil layers both above and deeper than 0.5 meters. For hydrocarbons there is little or no geographical correlation.
Strategy for contaminant mapping in Damhusdalen
Based on the results from the statistical evaluation the mapping status of the properties have been revaluated. Properties located outside the correlation distance of nearby boreholes are evaluated on the average statistical data.
Properties which have previously been registered as contaminated are still registered unless they are within correlated distance from boreholes.
The results of the evaluation
Approximately 30% of the properties in the residential area have been taken out of the soil contamination registry based on the statistic assessments for the area.
The Danish Regions are responsible for locating and remediating the contaminated sites posing a risk for groundwater that is used or can be used for drinking and/or pose a risk to human health.
The large number of contaminated sites within The Capital Region of Denmark necessitates a prioritization of the worst cases in order to maximize the profitability of the available resources. Today, initial prioritizing and risk assessment of individual contaminated sites depends on the specific solutes in question and their maximum concentration. Traditional transect methods with groundwater gradients and hydraulic conductivities are used to guide such prioritization. However, with improved knowledge on groundwater contaminated mass flux this could be optimized and make way for a more efficient use of available resources to target and remediate the most damaging or high-risk sites first.
As part of a still innovative development within the field of remediation of soil pollution, The Capital Region has joined collaboration with the company Sorbisense to develop a flux sampler. The flux samplers ability to give information about groundwater flux, flow direction and mass concentrations can help to an improved prioritization and risk assessment between individual contaminated sites. Moreover, it can be used to delineate soil contamination on already located contaminated sites and also to evaluate the effectiveness of ongoing remediation or natural attenuation.
Within the Capital Region the flux sampler is currently being tested on various projects, all initiated in 2014. These projects range from initial investigations where contaminated sites are located, to supplementary investigations, remediation projects and to reassessing remediation on older projects.
On 9 initial locations investigated for contamination, 10 flux samplers are installed with the purpose of getting an expression for the source strength and dispersal pathways (flow direction) of the specific solutes that have been shown with ordinary groundwater samples. The flux samplers are primarily installed in the secondary groundwater aquifer. This test should give us an indication of the benefits from using the flux sampler already in the initial stage of locating contaminated sites and guide the risk assessment and further prioritization.
In a remediation project with supplementary investigations where a heavy tar hotspot has been demonstrated near the vicinity of a groundwater abstraction well, 11 flux samplers are installed in various depths extending from 13-40 m.u.t. (primary and secondary aquifer). The purpose is to find the pollution dispersal pathways and flux to guide the remediation project of securing the drinking water. Here preliminary results show a coherent picture of both the flux and flow direction.
Finally, 5 flux samplers where installed in the secondary groundwater aquifer with the purpose of reassessing remediation on an older ongoing project. The challenge here has been relatively large variation in the results from the previously conducted monitoring events possibly due to a very low groundwater flow and inflow to the wells. Hence, the flux samplers are tested to estimate flux and flow direction in a low groundwater flow scenario.
OCCURENCE OF ANTIMONY IN SOIL AND GROUNDWATER AT FORMER SHOOTING RANGES
Jesper Alroe Steen (1), Maren Kann Hostrup (2), Mette Marie Mygind (2), Boerge Hansen (2), Henrik Soegaard Larsen (1), Jacqueline Falkenberg (1)
1. NIRAS A/S, Denmark.
2. Danish Ministry of Defense, Estates and Infrastructure Organisation, Environmental and Nature Section, Denmark
jas@niras.dk
BACKGROUND: Up until 2014, site investigations at military shooting range locations in Denmark have focused on lead as the primary contaminant of concern. Studies of sampling and analytical practice in other NATO countries have identified antimony as a contaminant of possible concern. Currently, Denmark has no quality criterion for antimony in soil or groundwater, which presents problems with respect to the drivers for site investigation and risk assessment.
Prior to site remediation at three shooting range locations, the Danish Defense have analyzed soil and groundwater samples in order to assess the occurrence of antimony. Subsequently, site remediation has been performed based on findings from the site investigations including the screening for antimony and the final risk assessment.
The site investigations have provided information on the presence of both lead and antimony as critical contaminants at former shooting range locations.
AIM: The aim of this presentation is to present recent studies on the occurrence of antimony in soils and groundwater at former military shooting ranges in Denmark. The presentation will include information concerning projectiles and activities that form the basis for the occurrence of antimony at shooting ranges, a correlation between the presence of both lead and antimony, and a comparison with contaminant levels at similar sites in other countries.
A secondary aim of the presentation is to highlight the process (focus on communication with environmental authorities) involved for site remediation if no national quality criteria are derived. The process requires the derivation of clean-up goals and approval by the environmental authorities based on documentation of the risk assessment process.
RELEVANCE: The presentation may be relevant to administrative personnel (national regions, environmental authorities etc.), consultants, entrepreneurs and others involved in site investigation and remediation at shooting range locations.
PROJECT: The project has included a literature study on the occurrence of antimony at shooting range soils, including a correlation for the presence in the soil of both lead and antimony (no national data existed).
Pre-investigations, including discrete soil and groundwater sampling, prior to site remediation, at three Danish shooting range locations have been performed in order to assess the occurrence of antimony. At the three locations, antimony was found in top soil in concentrations up to 515 mg/kg DW, 265 mg/kg DW and 12 mg/kg DW, respectively, and lead was present in concentrations up to 18,600 mg/kg DW.
As a significant supplement to the discrete soil sampling, Multi Incremental Sampling (MIS®) has been used to estimate average contaminant concentrations in target areas.
Groundwater samples have been collected from screened intervals in wells in the target area. Antimony concentrations in groundwater (ranging from non-detects to 2.2 µg/l) have been compared to the average antimony concentrations in soil in target areas illustrating the potential for leaching of antimony to the groundwater.
Based on these investigations, risk assessment has been performed in order to evaluate the potential risks to human health due to soil contact and on groundwater quality.
In relation to site remediation at the three specific shooting range locations, a proposal for a soil criteria for antimony has been prepared. The Danish EPA has undertaken to publish by early 2015, a national Danish soil and groundwater criterion for antimony which will be included in the presentation.
The presentation will also include data from the three site remediations, including the procedure for clean-up documentation.
CONCLUSION: Antimony and lead do co-exist in soil at shooting range locations. As the bullet core consist of 92-95% lead, 2-5% antimony and traces of other metals, contaminant concentrations at shooting range locations will be dominated by lead, but antimony can be a significant contaminant.
The mobility of antimony due to leaching from contaminated soil is greater than the mobility of lead, however both contaminants are strongly adsorbed to soil particles and transport in the unsaturated zone is thus greatly retarded.
Nevertheless, groundwater concentrations of antimony have been documented, indicating that the leaching of antimony does occur, although the calculated vertical transport times are very low.
For future investigations at shooting range locations, it will be relevant to sample for antimony, especially in relation to the pending national Danish soil and groundwater criteria for antimony.
The 1960’s and 70’s saw a growing awareness of the risks posed by soil and groundwater contaminations in The Netherlands. This was followed quickly by legislation on pollution prevention and maintenance of soil and groundwater quality in the 1980’s. Since then, thousands of potential groundwater contaminations have been researched and hundreds of sites have been remediated. More than 30 years later contaminations with chlorinated volatile organic compounds (VOCs) remain a persistent problem. Remediation is often more challenging than appears at first sight. Also on remediated sites, residual contaminations can still be present.
These historic contaminations originate mainly from spills at dry cleaners and metal processing sites. Besides perchloroethylene (per) and trichloroethylene (tri), vinylchloride (monochloroethylene, VC) is usually found in contaminated groundwater bodies. Vinylchloride is formed in groundwater as the result of the degradation (dechlorination) of per and tri. VC is highly volatile and harmful to humans, even at low exposure levels. As a result, the Dutch exposure model for assessing indoor exposure risks of volatile compounds in groundwater, VOLASOIL, often predicts an exceedance of the risk limit of VC in groundwater.
In practice, however, the presence of VC in the indoor air of buildings located over groundwater contaminations is rarely confirmed by site specific air measurements. For some time there is the presumption that degradation of VC in the unsaturated zone plays an important role in the rapid decrease of indoor air concentrations of this substance. Recent studies indeed show that VC degrades faster and on a larger scale under a variety of conditions, than was assumed earlier.
We present a simple approach to incorporate first order degradation in the existing equations for diffusive and convective transport of the volatilization model VOLASOIL. With this calculation method, it is possible to perform a more realistic assessment of the exposure of VC (and possibly other substances) due to volatilization and degradation in the unsaturated zone. The results obtained with the extended VOLASOIL model have been compared with site specific measurements. Combined with the most appropriate method for air sampling of VC, using canisters, it is possible to do a more extensive validation. This approach can also be implemented for VC in other human exposure models. With relevant degradation data the model can also be applied for other organic compounds (e.g. BTEX).
During large constructions of roads or structures, unexpected acid rock drainage (ARD) can be caused by local mineralization containing sulfides in the geology. The potential of ARD occurrence of a certain area sometimes must be assessed before initiation of any engineering earth works. However, it is difficult to assess the entire area through collecting rock samples and predicting the potential by laboratory tests, such as the acid-base accounting method. In this study, a new prediction protocol using a geochemical exploration survey technique of stream sediment is proposed. Sediment samples were collected at the case study area where a large development is expected in the future, and the contents of some major and heavy metal elements were compared according to the major geologies of the sampling points. The modified geoaccumulation indices (Igeo) of Fe, Pb and As could indicate a possible zone of pyrophyllite mineralization, which may cause the occurrence of ARD at the study area. Using the enrichment index of the three elements relative to the median values of the area, a high potential zone of ARD could be designated, which was in agreement with the laboratory ARD prediction tests of the rock samples. In the other areas with different mineralization processes, other metallic elements can be selected as indicators of the ARD potential. Likewise, the potential of the occurrence of ARD at an area can be assessed by evaluating the geochemical distributions and drawing the indicator elements for ARD through a stream sediment survey.
Biocides are common additives in building material. In-can and film preservatives in render and paint, as well as wood preservatives are used in order to protect façade materials from microbial spoilage. However, it is known that these compounds with fungicidal, bactericidal and algaecidal activity leach out of the material when it gets in contact with rainwater. While in city centers the total façade runoff drains on paved surfaces like streets and terraces and further into the sewer system, the runoff in residential areas drains to a certain amount to beds or the lawn surrounding the houses.
Based on a monitoring study of stormwater runoff from a residential catchment as well as direct façade runoff analysis, the present study was assessing the pollution of urban soil to biocides from building material. The stormwater runoff of a residential catchment in Silkeborg (Denmark) was monitored over nine months. The catchment covered 140 single family houses with a total façade area of about 24000 m2. However, only 25% of the total façade area was expected to release biocides (render, painted wood). Median concentrations of 45 and 52 ng L-1 (7 and 8 mg event-1) have been detected for carbendazim and terbutryn, respectively. The other studied biocides were usually lower. However, in some rain events the concentrations reached concentrations up to 1.8 µg L-1 (77 mg event-1), possibly resulting from freshly rendered or painted façades.
Emissions of freshly treated façades measured on artificial walls ranged from 1 to 10 mg m-2 event-1. Hence, the emissions of a freshly treated house with a façade area of 160 m2 might range from 40-400 mg event-1, since only one side of the house is exposed to the driving rain. Assuming the peak emissions of 77 mg in the stormwater monitoring to result from a freshly painted or rendered house, it is obvious that a huge part is actually draining directly to the soil and not to the sewer system. Consequently, the soil in urban areas is exposed to stormwater highly polluted by biocides which might affect the microbial community there.
The goal of this study is to develop a high-effective system for an ecological risk assessment and risk-based decision making for anthropogenic ecosystems, with particular focus to soils of the Kyrgyz Republic. The project is focused on the integration of Triad data including chemical, biological and ecotoxicological soil markers to estimate the potential risk of soils from highly anthropized areas impacted by the deposition of pollutants from mining operation. We will focus on technogenic area of Kyrgyzstan: the former uranium-producing province Kadzhi-Say.
Currently, Triad-based ecological risk assessment (ERA) and multi-criteria decision analysis (MCDA) for technogenic sites are not implemented in Kyrgyzstan. However, the vitality of such research is self-evident. There are about 50 tailing dumps and over 80 tips of radioactive waste, which are formed as a result of uranium and complex ores (mercury, antimony, lead, cadmium and etc) mining around the aforementioned unfavourable places. According to the Mining Wastes’ Tailings and Fills Rehabilitation Centre established in 1999 by special Government’s Resolution, one of the most ecologically dangerous uranium tailings is in Kadzhi-Say. Although uranium processing is no longer practiced in Kadzhi-Say, a significant number of open landfills and uranium ore storages remain abandoned along the vicinity of this settlement. These neglected sites have enormous problems associated with soil erosion and are known as “technogenic deserts”. The upper soil horizons are deprived of humus and vegetation, which favor the formation of low-buffer landscapes in the zones of maximum contamination. As a result, most of these areas are not re-cultivated and remain in critical environmental condition.
In this study Triad data for assessing environmental risk and biological vulnerability at contaminated sites is integrated. The following Triad-based parameters are employed: 1) chemical soil analyses (revealing the presence of potentially dangerous substances), 2) ecological parameters (assessing changes in microorganism’s community structure and functions, bioindication); 3) toxicological bioassays (utilizing classical endpoints such as survival and reproduction rates, genotoxicity). The output consists of 3 indexes: 1) Environmental Risk Index, quantifying the level of biological damage at population–community level, 2) Biological Vulnerability Index, assessing the potential threats to biological equilibriums, and 3) Genotoxicity Index, screening genotoxicity effects. This approach integrates a set of environmental Triad data obtained during study, which is carried out in order to estimate the potential risk from soils of highly human-impacted areas, called Kadzhi-Say, which have been primarily impacted by deposition of heavy metals and radionuclides.
The following tasks are solved:
• Characterization the physical-chemical parameters of soils with different sources of contamination. This task includes: (i) gathering historical data about land use; (ii) soil sampling campaigns for model technogenic sites for correct selection of the reference; (iii) assessment the mineralogical parameters, structural soil features, basic chemical and organic matter content; and (iv) mapping potential pollutant sources.
• Description the features of soil microbiota in the contaminated sites (in situ). Biological data (bioindication endpoints) include classical synecological parameters of bacterial and microscopic fungal (micromycetes) communities: (i) species indices of the taxonomic diversity of microbial communities; (ii) total biomass of bacterial and fungal cells, spores and mycelia; (iii) bio-morphological biodiversity and viability of fungal biomass – spore-mycelia ratio; and (iv) ratio of fungi and bacteria in the biomass of different samples of soil.
• Study of functional characteristics of soil biota. This category of testing includes parameters of fermentative activity of contaminated soils; determination of quantitative and qualitative content of enzymes, which carry out oxidizing reactions - peroxidase, catalase, and the reaction of hydrolysis - amylase, urease in soils. In addition with this multisubstrate and respirometric testing of samples to discriminate the fungal and bacterial activity after contamination of soils by different pollutants will be performed.
• Measurement toxicological endpoints in different model test-organisms. Bioassay responses obtained from organisms which represent different trophic levels: (i) producers (green algae and higher plant); (ii) consumers (crustacens and protozoan, mammalian cell culture), (iii) reducers (luminescent bacteria and pure culture of micromycete).
• Detection non-quantifiable attributes of microbe communities - presence of dark- pigmented toxicant-resistant fungi, pathogenic microorganisms, etc.
It will be created intellectual ecological models for the analysis of structural damage of the technogenic soils and soil cenoses based on complex of chemical and biotic parameters using multi-criteria decision analysis.
Acknowledgements. This work is supported by the ISTC grant (project KR-2092).
Carcinogenicity of benzo(a)pyrene (BaP) is one of the concerns related to polycyclic aromatic hydrocarbons (PAHs). This study investigates the mineralization of BaP using biocatalytic reactions of hemoglobin (Hb) and hydrogen peroxide (H2O2). Lab-scale oxidation tests (24 h) were carried out using 0.02 g Hb (2 g soil)-1 and 0.08 g H2O2 (2 g soil)-1. BaP degradation was 40% in the presence of both Hb and H2O2, while it was only 20 and 30% under the Hb-only and H2O2-only conditions. Toxicity test were performed with two luminescent bacteria, luxAB-marked YH9-RC and V. fischeri. Vibrio fischeri which is seawater originated halophilic microorganisms are commonly used for toxicity test. Janthinobacterium lividum is the groundwater borne microorganisms and well known as oligotrophic bacteria. The J. lividum YH9-RC used in this study is artificially generated luminescent bacteria possessing pUTluxAB vector of E.coli with harboring lux gene of V. fischeri. The concentration of BaP was decreased from 10 to 6 mg kg-1, and its removal efficiency was 40%. The EC50 values evaluated with two luminescent bacterial species were lower in BaP-contaminated soils compared to uncontaminated soils. The increase of EC50 was positively related with removal rate of BaP in both procedure using two luminescent bacterial species. The decrease of TU was positively related with BaP concentration degrade in both procedure using two luminescent bacterial species. Since the standard of soil toxicity has not published yet, examination of toxicity in both biocatalyst treated soils and uncontaminated soils is difficult. further study to create the standard of toxicity in soils will be necessary. In addition, this study using J. lividium YH9-RC showed more sensitive TU than that of V. fischeri. Advanced studies on J. lividium YH9-RC are essential. I suggested that toxicity test using freshwater microorganisms such J. lividium YH9-RC is more appropriate than that using seawater microorganisms like V. fischeri when soil samples are targeted.
The remediation of contaminated sites with important metal impacts in soil can be highly expensive, especially for conditions whereby in situ remediation or soil treatment is not technically feasible. In such situations a high resolution site characterization can contribute significantly to reducing the volumes to be excavated and disposed of on hazardous waste landfills at elevated unit costs.
The combination of a risk based approach, a high resolution field screening method and geostatistical techniques can contribute significantly to reducing the costs and the resourceintensity for site characterization and remediation, without compromising on the overall objective of land remediation, hence contributing to more sustainable remediation scenarios.
For a former battery production site with lead impact in soil exceeding 10 000 mg / kg dm, XRF (X-Ray Fluorescence) field screening was undertaken to support the high resolution site characterisation over an area of approximately 10 000 m². This method allows for obtaining a lot of data in a cost efficient and time efficient way with 100 direct analyses per day obtained on site by one field engineer, without sample transport and waste generation issues.
A geostatistical approach was used to determine the52 locations where XRF lead measurements were to be undertaken, with four discrete XRF samples over the vertical profile (first meter below ground surface with 25 cm intervals) for each of the 52 locations. The optimal location of these 52 sampling points was derived from historical information including lead laboratory analyses for 35 soil samples. A genetic sampling optimization algorithm aimed at putting the 52 new points in areas where they would contribute significantly to reducing the width of a 90% confidence interval associated with the mapping of lead concentrations. The algorithm tends to add points in areas where both concentrations and uncertainties are high and the algorithm should therefore efficiently contribute to reducing the overall uncertainty on the contaminant distribution in the subsurface. The selection of the XRF sampling points was undertaken in two phases with 22 sampling points for the first phase, the XRF results of which were then integrated in the sampling optimization algorithm to determine 30 additional XRF sampling locations for the second phase. In summary, the 52 XRF sampling locations were selected in a way that the overall uncertainty on the pollutant mapping could be reduced most efficiently.
A limited number of soil samples was sent to the laboratory to calibrate the 226 XRF field measurements taken at 52 locations. Estimated lead concentration maps where then produced with 3D kriging. Also stochastic simulation was used to produce probability maps expressing the likelihood to exceed the risk based remediationtarget value, allowing for optimising the contaminant mass removal and impacted soil removal still respecting the overall remediation objective.
Cd containing pigments are used in artists’ paints since begin of 19th century. CdS (PY35, Cadmium yellow) is one of the most important pigments in this group. More recently they are in the focus of environmental scientist due to possibly negative effects the use of these pigments may have for the environment. One possible pathway into the environment is cleaning used brushes with water and subsequent waste water treatment in sewage plants. The Cd sulfide settles together with the activated sludge in the sedimentation basin. Due to its high nutrient content this sludge is often used as fertilizer for agricultural used soils. This application will also transfer the Cd sulfides to the soil. For risk assessment knowledge about mobilization of cadmium from this pigment is necessary as mobile Cd can be transported to the groundwater or be introduced in the human food chain after up take by plants. Cd is toxic to aquatic organism and to humans, is suspected to cause cancer and harmful to the bone structure.
The Cd sulfide itself is sparingly soluble. However oxidizing or acidic conditions result in free Cd ions. Thus, the mobilization potential of Cd has to be determined under realistic environmental conditions. Column percolation tests are often used for investigations of leachable amounts as there a good compromise between effort, gained information and realistic conditions. In contrast to lysimeter studies accelerated experiments are possible enabling predictions for prolonged scenarios.
In this work the results of such percolations test under different redox conditions are presented. Sewage sludge spiked with Cd pigments was mixed with soil containing different amount of organic carbon. These materials were percolated using artificial rainwater up to a liquid to solid ration of 10. The redox potential was measured directly after the column outflow on-column. Eluate samples were taken during this time period and analyzed for Cd concentrations. Conductivity, pH-value, turbidity and DOC concentrations were also measured.
The redox potential is decreasing fast after start of the percolation and shows a clear relation to the organic carbon content of the soil material: eluates of columns with higher organic carbon show a slower decrease in redox potential. In accordance to the redox potential more Cd is released from soils with higher redox potential.
LEACHING AND TRANSPORT OF PERFLUORINATED COMPOUNDS AT A FIRE FIGHTING TRAINING SITE AT AN AIRPORT IN NORTHERN NORWAY
Øystein Seim Solaas (1)*
Gijs D. Breedveld (1, 2)
Beate Løland (1)
(1) Department of Geosciences, University of Oslo, PO Box 1047 Blindern, 0316 Oslo, Norway
(2) Norwegian Geotechnical Institute, PO Box. 3930 Ullevål Stadion, 0806 Oslo, Norway
* Corresponding author e-mail: o.s.solaas@kjemi.uio.no
Background
Perfluorinated compounds (PFCs) have for a number of years been spread to the environment at Norwegian airports through the use of aqueous film forming foam (AFFF) as a firefighting agent. PFCs are a group of chemicals that are persistent in the environment, and bioaccumulate in organisms. One PFC which has received most attention is perfluorooctane sulfonate (PFOS), which is identified as a priority hazardous substance in EU's water framework directive (WFD) (2013/39/EU).
Although the use of PFC containing AFFF has ceased, this investigation has revealed that high amounts of PFCs are still present in the soil at an airport in northern Norway. PFCs are continuously leaching from the soil to nearby water bodies. PFOS is the dominating PFC still present in the soil. The concentration of PFOS in the receiving inland surface water is exceeding the environmental quality standard set forth in the WFD.
Aim and relevance
The aim of this project was to determine the occurrence, fate and transport of PFCs at the airport. This was achieved through water and soil analysis and column experiments. The results have been used to develop a model for determining the fate and transport of PFCs at the site.
Project
Determination of PFCs in soil and soil water was carried out at several locations downstream a firefighting training site at the airport. Column experiments were carried out on undisturbed soil profiles to determine the partitioning characteristics of PFCs in the soil. This enabled modeling of the behavior of PFCs in the soil and hence an estimate of the environmental impact on recipients could be reached.
Conclusion
The results from the investigation at an airport in northern Norway have been used to develop a model for determining the fate and transport of PFCs. The model will be used to determine the potential effect of remedial actions at the site.
AP Reis1,2, I Santos1, S Costa1, C Patinha1, Y Noack3, J Wragg4, AJ Sousa5
1GEOBIOTEC, Departmento de Geociências, Campus Universitário de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal
2CICECO, Departmento de Química, Campus Universitário de Santiago, Universidade de Aveiro, 3810-193 Aveiro, Portugal
3Aix-Marseille Université, CNRS, CEREGE, UMR 7330, BP 80 13545, Aix en Provence Cedex 4, France
4British Geological Survey, Keyworth, Nottingham, NG12 5GG, United Kingdom
5CERENA, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
house dust
This study reports to data obtained from a pilot survey focusing on household dust collected from 20 home residences in Estarreja, a Portuguese industrial city. The study aims mainly at investigating the influence of the dust mineralogy in the oral bioaccessibility of Cr and V. Nevertheless, the relationships between concentrations of Cr and V in dusts collected from indoor and outdoor areas of the house, as well as their relationships with other chemical elements, were also investigated. An increased knowledge on such relationships is important to better understand the bioaccessibility estimates. A total of 21 households were recruited for the pilot study: 19 households in the urban area of Estarreja, forming the exposed group, plus 2 households from residential areas with no anticipated Cr and V that were used for comparison. The mineralogy of the indoor dusts, which was determined by X-Ray diffraction, is simple and composed by variable proportions of quartz, K-feldspar, Na-plagioclase and calcite. Semi-quantitative analysis of 55 chemical elements, including Cr and V, was carried out by Inductively Coupled Plasma - Mass Spectrometry. Average total Cr concentrations are more elevated in indoor than in outdoor house dusts and the difference is statistically significant (p < 0.05). For V, average concentrations are more elevated in outdoor house dusts and the difference is also statistically significant (p < 0.05). However, concentrations in the house dusts are similar to the ones obtained for control sites. Total metal concentrations in indoor dusts are not correlated with concentrations in the outdoor dusts, neither for Cr nor for V. Principal component analysis (PCA) applied to the entire data set shows that Cr and V are separately assigned to two uncorrelated clusters. It is worthwhile to point out the strong correlation obtained for V and Mn. The joint projection of variables and samples in the 1st PCA factorial plane also shows that the Cr-containing group of elements clusters due to metal concentrations in outdoor dust samples, while the V-containing group is associated to indoor dust samples. These results indicate that, for the dataset under study, outdoor metal sources are probably prevalent for Cr while indoor sources may be important contributors to the total V concentrations in the house dusts. Oral bioaccessibility measurements were obtained using the Unified BARGE Method (UBM) on a sub-set of 9 indoor dusts. The results used in this study report to the ones obtained in the gastric phase (G-phase) of the UBM protocol that provided higher extracted concentrations and better repeatability values, and was therefore used as a surrogate of oral bioavailability. The bioaccessible fraction (BAF) of Cr in the dusts varies between 16 and 35% and does not correlate with total Cr concentrations. Similar results were obtained for V that has BAF values ranging from 34-55%. Thus, important metal fractions are probably unavailable for absorption in the gastrointestinal tract following incidental dust ingestion. Investigation on the relationships between metal concentrations (total and bioaccessible) and mineralogy was carried out through simple linear regression analysis. No relationships were found between total concentrations of both metals and the mineralogy of the dust. However, for V the results show that increasing proportions of calcite in the bulk sample correspond to increasing estimated BAF values. Yet, the same relationship was not obtained for Cr. Several factors can be proposed to explain this distinct behavior for Cr and V.
Decabromo diphenyl ether (deca-BDE or BDE209) is the fully brominated congener in the family of polybrominated diphenyl ethers (PBDEs). Since the 1970s, PBDEs have been added to polymeric materials to inhibit their flammability. More recently, neurological and endocrine disrupting effects of PBDEs have been found alongside the detection of PBDEs in a wide range of biotic and abiotic samples from urban areas to the most remote regions such as the Arctic and Himalayan Plateau. Subsequently, the Stockholm Convention meetings (2011) added some of the lower brominated congeners to the list of Persistent Organic Pollutants (POPs), and in October 2013, the inclusion of Deca-BDE to the POPs list has been proposed. More scientific information about Deca-BDE fate, transport, and environmental availability is essential to support this evaluation alongside development of remediation strategies to address its presence in the environment.
This work investigates the adsorption and desorption kinetics of deca-BDE on four soil fractions: sand, silt, kaolin for the clay fraction, and peat to simulate the soil organic matter. Kinetics are calculated using the OECD batch method. In order to close the mass balance, an analytical method has been developed for the analysis of deca-BDE in both water and soil fractions. Solid samples are extracted through accelerated solvent extraction (ASE) and water samples by evaporation and substitution with acetonitrile. Concentrated solutions are than analysed by high performance liquid chromatography (HPLC) equipped with a UV detector. The HPLC analytical method has a limit of detection of 0.03mg/L and limit of quantification of 0.09 mg/L. The only inconvenience of using a UV detector instead of a mass spectrometer is the coelution of interference peaks, which could not be distinguished from the analyte. This problem is limited to the highly organic peat samples.
The experimental kinetic curves are fitted with first order kinetic models with one and two compartments. The two-compartment kinetics model has more degrees of freedom and fits the experimental curves better. The physical explanation commonly used to justify the two compartments model is to assume that each compartment represents a portion of soil active sites characterised by a different time that has been reached by the analyte. This research explores soil components and mixtures of soil components to simulate field-relevant conditions. This approach is used to evaluate the effects of heterogeneities in a controlled manner. The kinetics from soils composed in different proportions by the four soil components are compared with the linear combination of the single kinetics. This method also allows for the evaluation of the two-compartment model and whether it could be justified by different kinetics on the soil components.
In addition to the soil constituent properties, including surface interaction and internal porosity, that are taken into account, soil wetting, inter-particle porosity, and compaction may affect the mobility. The resulting information about decaBDE adsorption and desorption is invaluable to efforts to understand its mobility in the environment and develop remediation strategies that can be applied in the affected areas.
1C.1 - Bio-remediation
1C.2 - Chemical oxidation
1C.3 - Hydrocarbons
1C.4 - Heavy metals
Laboratory and field data are presented underpinning a new technology development for achieving very fast risk reduction in the groundwater pathway (days) and for securing contaminant destruction to stringent targets (low part per billion range) using a passive, low-energy approach. The technology is particularly suited to the management of large, diffuse spreading plumes, and for deep, low concentration plumes in complex geologies. The technology requires no energy or intervention post application, and is expected to remain functional for decades.
The technical innovation allows for wide dispersion of a sorptive medium in the aqueous subsurface. The medium has a dual function; it sorbs contaminants, quickly removing them from the mobile phase, and provides a high surface area matrix favorable for microbial colonization and growth. Contaminant availability within a risk pathway is therefore reduced while at the same time contaminant destruction is accelerated.
Upon reagent injection, target contaminants partition out of the aqueous phase and into the reagent matrix, thereby removing mobile contaminants from the immediate risk pathway. Concentration of the contaminants in this manner, in a matrix conducive to degrader colonization and activity, results in a direct increase in the overall instantaneous rate of contaminant destruction, given the quasi first-order biodegradation kinetics characteristic of environmental systems. This phenomenon can be especially important at low contaminant concentrations, which may otherwise prove insufficient to support appreciable growth and activity of a degrading microflora. When necessary, the medium can be applied in combination with compatible electron donors / acceptors.
The technology can be employed to inhibit spreading of contaminant plumes, to protect sensitive receptors, or to prevent contaminant migration across property boundaries. The technology is also postulated an effective tool for control and treatment of groundwater contamination associated with low-permeability porous formations and matrix back-diffusion, promoting diffusion out of the immobile porosity while preventing groundwater impact.
Field studies confirm wide-area dispersion, with order of magnitude (>90%) dissolved-phase concentration reductions secured at the test sites post-application sampling, increasing to two orders of magnitude (>99%) within two months for both chlorinated solvent and hydrocarbon species alike. Laboratory and microbial quantitative array field data provide confirmation of post-sorption degradation enhancement, with laboratory studies describing a significant increase in the rate of contaminant destruction in biotic matrix systems compared to abiotic matrix and biotic non-matrix controls.
Biofuels, such as biodiesel, are increasingly being used as fossil fuel replacers in transportation due to issues associated with climate change and energy security. Fossil diesel is a complex mixture of hydrocarbons, and includes aromatics such as toluene. As it is with any other fuel, inadvertent releases and transportation accidents have lead to soil and groundwater contamination.
Although biodiesel is increasingly being used, little is known about its fate under different redox conditions, such as nitrate-reducing conditions, and the impact on microbial diversity. In addition, the presence of biodiesel may negatively impact toluene biodegradation; however, limited information is available concerning nitrate-reducing conditions. Therefore, the aim of this study was to examine the fate of biodiesel under nitrate reducing conditions and its impact on both microbial diversity and toluene biodegradation.
Microcosms were setup using approximately 5 g of sediment collected from two contaminated sites with 100 mL of anaerobic media in 125-mL serum bottles. The initial amount of nitrate present was 2 g/L. Microcosms were purged for 15 minutes with nitrogen gas and sealed with Teflon-lined septa and aluminum crimp caps. Afterwards, the batch reactors were incubated statically, upside down, in the dark, at 25 °C. Tests included: biodiesel alone, biodiesel + toluene, and ‘as is’ and autoclaved controls.
Headspace samples were periodically removed and analyzed for toluene biodegradation. Aqueous samples were collected for the determination of biodegradation products and electron acceptors (volatile fatty acids, nitrate, and nitrite). Additional nitrate was added as needed to maintain nitrate reducing conditions. Finally, microbial community shifts between the biodiesel in the presence and absence of toluene were monitored by extracting total DNA in time series aqueous subsamples. Bacteria and Archaeal community shifts were evaluated using the fingerprint denaturing gradient gel electrophoresis (DGGE) technique.
Acknowledgements: This work was supported by FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT – (Portuguese Science and Technology Foundation) under project numbers PTDC/AAG-TEC/4403/2012 and PTDC/AAC-AMB/113973/2009.
Leakage of chlorinated solvents into limestone aquifers from contamination in overlying deposits and long-lasting back diffusion from the limestone matrix pose an increasing threat to drinking water supplies, e.g. in Denmark. Often dechlorination of PCE and TCE contamination in limestone accumulates cis-DCE due to inadequacy of advection-based remediation technologies to deliver bioremediation additives. Therefore, there is a need for a remediation scheme capable of establishing contact between the contaminant, bacteria capable of degrading cis-DCE, and donor within the low permeable limestone matrix. EK offers some unique transport processes, which potentially overcome the diffusion limitations of ERD. A novel technology combines ERD and EK for enhanced delivery. The combined technology (EK-BIO) has shown promising results in the low permeable media clay. However, until now no studies have been performed with limestone.
A bench scale study of transport during EK-BIO in limestone was performed. Focus was on the transport abilities of EK for enhanced delivery of the donor lactate and a bacteria culture containing the dehalorespiring bacteria Dehalococcoides (Dhc) in limestone cores contaminated with cis-DCE. For the experiment, methods were developed for sampling of intact bryozoan limestone cores, saturation and contamination of the limestone cores using vacuum properties, and for monitoring throughout the limestone cores. In addition, an experimental set-up was designed to comply with the challenges of EK-BIO in limestone, e.g. the strict anaerobic bacteria, volatile contaminants and extreme pH developments prompted by electrode processes. The latter can be severe for the degrading bacteria if not managed.
An experimental set-up was successfully designed. However, issues with the recirculation pumping for neutralization of pH were experienced. Therefore, suggestions for improvements of the experimental design were made. The performed preliminary test and assessment of EK-BIO in limestone revealed a critical pH development in the electrode compartments. Nevertheless, the buffering capacity of the limestone maintained a pH range within the limestone appropriate for the Dhc. Observations on transport processes included faster diffusion in the control reactor without EK, than predicted. However, the delivery of the donor lactate was uneven, whereas migration of bacteria was not observed. For the reactor exposed to EK, lactate was delivered more evenly by electromigration causing an increase in electric conductivity. Furthermore, fermentation of lactate with an increase in pH indicated migration of bacteria by electrophoresis. Whereas, an initial test on EOF in limestone as well as the assessment of EK-BIO indicated that the properties of limestone hindered the establishment of EOF as opposing to clay.
During the experimental work on EK-BIO in limestone, EK was demonstrated to be promising in establishing enhanced contact between the donor lactate, bacteria and the chlorinated compound cis-DCE within the limestone matrix. Therefore, degradation is expected to occur. Thus, back diffusion limitations in the limestone matrix potentially are overcome, which is essential for the overall time perspective of a remediation.
Microbial populations and functions associated with the degradation of the aliphatic and PAHs fractions of crude oil in microcosms inoculated with an industrial polluted soil
Andrés Izquierdo1,2, Joaquim Vila1, Corinne Petit3, Pierre Peyret3, Alma Koch2 and Magdalena Grifoll1
1Department of Microbiology, University of Barcelona, Barcelona, Spain
2Laboratorio de Microbiología-Biotecnología, Universidad de las Fuerzas Armadas – ESPE, Sangolqui, Ecuador
3Laboratoire Microorganismes : Génome et Environnement - UMR 6023, Universite Blaise Pascal, Clermont Ferrand, France
The metabolic pathways for bacterial degradation of alkanes and PAHs are well established. However, there is still little information on the microbial processes dealing with alkylated derivatives of PAHs, which are the most abundant polyaromatic compounds in petroleum products. Despite several evidences exist pointing to their oxidation through two alternative pathways, the cometabolic monoxygenation of methyl groups or their accommodation through traditional PAH degradation routes, the actual environmental relevance of both processes is still unclear. In addition, there is limited information on the effect that the aliphatic fraction, predominant in oil derivatives, may have on the degradation of the aromatic fraction. Here, applying a combined phylogenetic and functional analysis of the microbial communities, we aim to decipher how the presence of aliphatics may influence a shift in the microbial processes determining the fate of PAHs, and especially alkyl-PAHs.
To gain insight into these processes, an industrial soil polluted with a mixture of oil derivatives, and previously remediated in biostimulated aerobic biopiles, was used as inoculum for lab-scale microcosms spiked with the aliphatic and/or aromatic fractions of a weathered crude oil. The microcosms were incubated for 30 days, and the fate of the different components of the aliphatic and aromatic fractions were monitored throughout the treatment by GC-MS. Shifts in microbial community structure and functions were monitored by high throughput sequencing (tag-encoded 454-pyrosequencing) and functional screens using PCR-amplification of monooxygenase genes (AlmA, AlkB and CYP153A) and functional microarrays including a number of dioxygenase gene probes.
The bulk of alkanes were completely removed from the media after 15 days of incubation and, interestingly, their presence had a synergic effect on the removal of PAHs, increasing their rates and extent of degradation (73 and 59%, with and without alkanes, respectively). The populations linked to the utilization of alkanes (Actinobacteria), PAHs (Alphaproteobacteria closely related to Sphingobium) and to the mixture of both fractions (a succession of Actinobacteria and Alphaproteobacteria) were identified. Their functional analysis revealed that, in accordance with the phylogenetic analysis, the biodegradation of alkanes was mainly catalyzed by alkane hydroxylases related to AlkB and CYP153A from Gordonia and Nocardia, while PAH biodegradation was mainly linked to biphenyl dioxygenases related to members of Sphingobium. In the presence of both fractions, the combined action of AlkB and CYP153A monooxygenases together with biphenyl-dioxygenases could explain the synergic effect of alkanes on PAH biodegradation.
Biomass from wetlands is a natural material able to decrease nitrate present in groundwater before the discharge to rivers or lakes. The desired predominant mechanism of nitrate removal is heterotrophic denitrification by supplying organic carbon that, additionally, enhances anoxic conditions in subsurface environment. Nevertheless, an excess of organic matter could activate other mechanisms as Dissimilatory Nitrate Reduction to Ammonia (DNRA). The leaching of these organic matter rich soils (e.g. peat) could be a mechanism to promote denitrification in deeper subsurface layers and, thus, avoiding high concentrations of organic matter and DNRA pathways.
In the present work, the assessment at laboratory scale of the denitrification capacity of leachates of wetland soils in which Phragmites sp and Arundo donax reeds have been growing for years has been studied. As a first step, samples of soils and degraded reed biomass were collected in two wetland zones in the Llobregat river basin (Barcelona) in February 2014.
Four leaching procedures (Soxhlet cycles, percolation in a column filled with material, shaking with water and lixiviation by using a normalized leaching test) were tested to extract the maximum of Dissolved Organic Carbon (DOC) at room temperature from the biomass samples. Values of DOC in the materials ranged from 10 to 31 mg•dm-3, obtaining the best results for normalized leaching test. The UV signal at 254 nm was also used to assess quantitatively the presence of aromatic compounds in the leachates. The ratio of this signal to DOC reported values from 0.03 to 0.06 A.U•l/mg, that are in the range of fulvic acid (0.05 A.U.dm3/mg). Nitrate in the leachates from all the biomass showed values above 20 mg•dm-3, with the exception of degraded Arundo donax in soil very close to the river that exhibit values below 2 mg•dm-3.
All these characterized leachates were filtered and used as matrix in two batch experiments, where nitrate and inoculum obtained from soil of the wetlands were mixed. The reaction was performed for a period of 5 to 12 days, showing complete denitrification when DOC was replaced by glucose 100 mg•dm-3.
A third leaching experiment was prepared by shredding green Arundo donax leaves sampled in May 2014. DOC of these leachates reached 523 mg•dm-3 and total nitrogen 49.8 mg•dm-3.In this case the leachate was not filtered.
Results showed a very low denitrification (< 10% nitrate elimination) for the three experiments for most of the materials, with the exception of the soil with degraded leaves of Phragmites sp and the green Arundo donax leaves that showed more than 50% and complete elimination of nitrate respectively.
As a conclusion, the leachates of biomass materials sampled in February were not able to leach important amounts of DOC and could not denitrify, with the exception of degraded Phragmite leaves sp. Soils showed the presence of UV-absorbing compounds that could be associated to complex organic matter as fulvic acids. Green Arundo donax leaves sampled in May allowed to obtain a leachate able to perform complete denitrification, mainly due to high DOC. In these vegetal materials nitrogen is important, as could contribute initially to the nitrate load of contaminant or release ammonium.
The present research work has been funded by the Spanish Ministry of Economy and Competitivity through project ATTENUATION (CGL2011-29975-C04-03, Natural and Induced Attenuation of groundwater pollution from agricultural and industrial sources).
Our objective was i) to assess the ability of microorganism from a plume to degrade chlorinated solvents to which they are exposed in situ and ii) to determine optimal substrate conditions to stimulate their ability to degrade these products. We monitored chloro-ethene and chloro-ethane, but also chloro-propane for which one little is known on its fate in the environment.
Three springs were selected at different distances from the Dense Nonaqueous Phase Liquid source in order to have one monophase water sample (W1) (15 m downstream the DNAPL) with perchloroethene (PCE), trichloroethene (TCE), dichloroethene (DCEcis and DCEtrans) are at the ppm level, a second water sample (W2) (250 m downstream) with these chloro-ethenes at the ppb level and a final diluted site (W3) (1.5 km downstream) with no PCE detected, TCE and DCEtrans at the limit of quantification level (2 ppb), and therefore with DCEcis (30 ppb) as main quantified contaminant. Vinyl chloride (VC) ranged from 0.3 to 0.008 ppm in these waters. Chloro-propanes were also found at the ppm level in the first water, especially the 1,2-dichloropropane (DCPa) (2.5 ppm).
Abundance of the total microbial community in these 3 water samples was assessed by qPCR (16S rRNA) and microscopic counting, and abundance of the bacterial community degrading chloro-ethene solvent was assessed by qPCR of reductive dehalogenase genes (pceA, tceA, pdrA, bvcA, vcrA). Water was placed in sacrificial batch units in triplicates with no substrate addition or with lactate (3 mM), acetate (3 mM), soya oil (15 g/L), molasses (0.7 g/L) as carbon substrate to stimulate reductive dechlorination. Degradation of the chlorinated solvent was monitored by GC/FID conditions every 2 weeks for lactate-spiked unit and every month for 4 additional conditions, during 5 months.
Preliminary results showed that after one-month incubation, concentrations in PCE, TCE, DCEtrans and VC, significantly decreased to a similar level in presence of lactate or molasses (p < 0.05) in water W1. However in W1, DCEcis and DCPa concentrations did not decreased after one-month incubation. In water W2, PCE, TCE, DCEtrans, VC and DCEcis significantly decreased after one-month incubation with lactate. In the water W3, DCEcis decreased after one-month incubation with lactate. Degradation analyses in the additional substrate conditions are under-going, also additional sampling dates to be performed are meant to generate biodegradation rate.
In conclusion, preliminary results suggest that i) bacteria able to degrade chlorinated solvent were present in the three tested water samples, ii) in the water W1, molasses and lactate would have similar potential to stimulate their activity, and iii) DCEcis degradation was not detected within one-month incubation in a sample with high level of PCE and TCE, such as W1, possibly because it is also the product of their degradation; when concentration in PCE and TCE were lower (W2) or not detected (W3), DCEcis degradation was initiated within a month.
The present study will provide valuable information for in situ bioremediation, and more specifically regarding choropropanes degradation. The present work will enable to select optimal conditions for further optimization in column units, then in a pilot-scale plant on site.
Anthropogenic organic chemicals like pesticides (2,4-Dichlorophenoxyacetic acid and Glyphosate) are deliberately released in major amounts to nearly all compartments of the environment. Soil as a complex matrix provide a wide variety of binding sites and are the major sinks for these compounds. Xenobiotics entering these complex systems may undergo various turnover processes. They can be degraded chemically (e.g. photolysis), biologically by microorganisms, volatilised leached to the groundwater, taken up by living organisms or immobilised.
The biological degradation of organic contaminants in soil generally results in the formation of metabolites, microbial biomass, CO2 and “bound” residues (non-available form). The extraction of these metabolites from soil allows the estimation of microbial activity; however, this activity could be modified thought the variation of physical, chemical or biological factors. Many studies have shown that parameters like the temperature, the organic matter content and the acidity of the soil are key factors to determinate the degradation rate of some organic contaminants and the way in which they are released into the environment.
Nowadays, enhanced transformation of contaminants into “bound” residues (non-extractable form) has been proposed as an alternative remediation method for polluted soils. Nevertheless, this kind of residues may pose a potential risk for environment due to their chemical structure and possible remobilization under different conditions. Some part of these residues may be “biogenic” because microorganisms use the carbon and nitrogen from the pollutant to form their biomass components (fatty acids, amino acids) what can result in the overestimation of the risk of “bound” residues in soil
MTBE has been added to gasoline since 1970's in order to improve engine performance and enhance air quality. Worldwide, It has been one of the highest production volume organic chemicals. In 1999, the annual world consumption of MTBE was more than 21 billion tons. However after only a few years of intense use, MTBE has become one of the major environmental concerns due to its chemical properties and widespread contamination of groundwater.
In situ aerobic bioremediation of MTBE is a cost effective technique which is used in many contaminated gasoline sites, but becomes increasingly more difficult as the concentrations of MTBE rise.
Due to the very high solubility of MTBE, many sites exhibit contamination by MTBE in the range of hundreds mg/L which are difficult to bioremediate. Moreover, the rates of degradation of MTBE and TBA are generally lower in comparison to the degrading rates of similar volatile organic compounds as Benzene, Toluene and Xylene. In many cases, the presence of those volatiles can even inhabit the degradation of MTBE.
The ability to biodegrade MTBE under aerobic conditions is possible by a limited number of microbial species, hence their presence in the contaminated site may become a limited factor for the successful remediation.
The remediation of high concentrations of MTBE in groundwater proved successful only when microflora resistant to high concentrations of MTBE was present and oxygen could be supplied in sufficient amounts.
Lab experiments proved relatively easy to provide these conditions relatively to actual field scale tests.
In this presentation we discuss the degradation of MTBE under high concentrations in laboratory and field scales. The laboratory experiments showed reduction of 40%-52% of the concentration of MTBE in relatively short time 12 days, when the initial MTBE concentration was up to 550 mg/L.
We will describe the enrichment of groundwater with an appropriate natural culture into highly contaminated groundwater, lacking the natural ability to biodegrade MTBE. This study provides insights into the conditions necessary for the degradation to occour.
Hydrophobic compounds such as polycyclic aromatic hydrocarbons (PAH) exhibit a strong tendency for adsorption on subsurface material. Due to the low solubility of such substances the determination of degradation kinetics is difficult. Reliable data for kinetic parameters such as growth rates and half-saturation constants are thus rare for PAH-degrading strains.
We performed degradation experiments with phenanthrene and pyrene and three Gram negative PAH-degrading strains (Novosphingobium pentaromativorans, Sphingomonas sp EPA505 and Sphingobium yanoikuyae) (Adam et al. 2014) as well as with two strains of mycobacteria (Mycobacterium rutilum and Mycobacterium pallens). Phenanthrene or pyrene were present as microcrystals in suspension concentrations from 10 to 400 mg/l, providing initially non-limiting conditions for growth. Chemical concentration and protein concentration or optical density (for the mycobacteria) were measured over 6 to 12 days. We developed and applied a numerical model for simultaneously calculating (i) dissolution kinetics of the substrate (dissolution from microcrystals into solution), (ii) substrate metabolism (Michaelis-Menten kinetics) and (iii) microbial growth (Monod kinetics with decay).
New and improved experimental kinetic data will be provided for PAH-degrading strains which are well-known from the literature and were isolated from various contaminated sites. The new dynamic model for desorption and metabolism describes mass-transfer of the substrate, taking simultaneously into consideration chemical activity, sorption and dissolution processes, metabolism and growth as well as cell maintenance and decay processes in non-steady-state. By inverse modeling we successfully determined kinetic parameters for the rates of dissolution, metabolism and grow from the experimental observations.
As a surprising outcome of the simulations, variations of the initial amount and of kinetic data of the degrader bacteria do not strongly affect the overall substrate turnover. As long as the dissolved concentration is sufficiently high, the degrader strains will grow, until a balance between dissolution of substrate and bacterial metabolism is reached. This balance was reached within a day or less in all experimental set-ups. For longer time periods, the amount of PAH that is ultimately degraded rather depended on the ad/desorption rates, and hereby on the substrate flux to the microbes, than on the Monod and Michaelis-Menten parameters of the strains. The model was subsequently used to simulate bioremediation options of aged PAH contamination in soils, for the optimization of treatment processes and for the assessment of residual, non-degradable concentrations remaining after various treatment options (see presentation of Rein et al., at AquaConsoil 2015).
Rein A, Trapp S, Adam IKU, Miltner A, Smith K, Marchal G, Karlson UG, Mayer P, Kästner M. 2015. Simulation of bioremediation options by microbial degradation of aged PAH contamination in soils. Presentation at AquaConsoil 2015.
Adam IKU, Rein A, Miltner A, Fulgêncio ACD, Trapp S, Kästner M. 2014. Experimental results and integrated modelling of bacterial growth on insoluble hydrophobic substrate (phenanthrene). Environ. Sci. Technol. 48 (15), 8717-8726.
Organic contaminants in the soil is a widespread problem that not only may cause damage to local biota, but also poses an ecological and health threat if the contaminants spread to groundwater aquifers and water ways. Therefore sites known to be contaminated should always be assessed preferable by performing both an ecological risk assessment and a health risk assessment. Monitored natural attenuation (MNA) is in some cases a reasonable approach, but risk assessment often calls for active remediation measures. For more than 20 years we have tested various approaches for enhancement of bioremediation of sites polluted by organic contaminants. Through collaboration between research facilities, contractors, and site owners, more than 30 actual sites presenting typical problems have been targets for testing and optimization, first by laboratory modeling, and then by applying lab experiences in pilot scale and application full scale. Samples from the sites were used in controlled laboratory conditions to build micro- and mesocosm- setups in which biological, physical, and chemical treatments were tested and combined, with the main goal of achieving optimal biostimulation and contaminant degradation. As soon as lab results were available, these were utilized for in situ field purposes. Lab and field tests were run in parallel, so that each new challenge in the field treatment generated modifications in the laboratory testing, and each new full scale treatment method was preceded by laboratory modeling. Successful bioremediation was achieved in most of the target cases. Lab testing also created the knowledge of when not to use bioremediation, and this can be regarded as one important utility of our results. While old contaminated sites often can rely on an adapted indigenous microbial community, new spill sites may be less responsive to mere biostimulation, and therefore more active treatment measures may be required. One bottleneck for a more widespread use of in situ methods is the great variability in the usefulness of each type of treatment. Vital for success is a thorough knowledge of the site and a variety of methods to choose from and, when necessary, to combine. Two successfull full sale treatments will be presented in detail. Both treatments were done in inhabited urban areas – biostimulation in the city-center of Mikkeli and “bioflushing” in Lintuvaara in Espoo. We have tested and optimized various combinations of biostimulation with nutrients and biosurfactans, bioaugmentation, extraction, electro-kinetic methods for liquid circulation and temperature elevation, and the use of previously contaminated soil as a seed for degraders. No single method to be used in situ can be named universal and useful in all cases. There always needs to be an array of methods to choose from, and it may be important to apply different methods at different stages of the process. Furthermore, every case should be evaluated separately, taking into account local conditions, type of contaminant, available time, etc. Only with these notions in mind is it possible to make in situ treatment a viable alternative to excavation of contaminated soil.
The purpose of the field-scale study was to evaluate the effectiveness of biostimulation and bioaugmentation for in situ biodegradation of chlorinated solvents in groundwater. Elevated levels of tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene, were detected in groundwater. The natural attenuation evaluation showed that reductive dechlorination was occurring in several of the on-site monitor wells where the dissolved oxygen (DO) concentrations were less than 1 mg/L. However, the oxidation reduction potential (ORP) significantly varied in on-site and off-site wells.
The results of bench-scale testing indicated that a variety of carbon substrates were effective at reducing the DO to levels that were favorable for reductive dechlorination. The lactate amended bioaugmented microcosms showed the highest level of reductive dechlorination, followed by EOS® amended. However, the indigenous microbial population was not able to successfully degrade PCE to ethene. When a microbial consortium including Dehalococcoides was added to the microcosms, complete reductive dechlorination was observed.
A pair of recirculation wells was installed to inject the carbon source and microbial population into the groundwater. After a push-pull test was performed to evaluate the mobility of the microbial amendment, lactate was injected to promote highly reduced conditions in the groundwater. Once the ORP was less -150 mV, the Dehalococcoides consortium was injected into the groundwater and recirculated using the paired recirculation wells.
Within 3 months after carbon substrate injection, more than a 70% reduction in PCE and TCE was observed in the downgradient monitor well. Likewise, there was a significant decrease in ORP in the impacted wells. This presentation will discuss how the amendments impacted the chlorinated solvent concentrations, microbial community and chemistry of the groundwater in the area around the recirculation wells compared to non-impacted wells.
ENHANCED REDUCTIVE DEHALOGENATION OF CHLOROETENES BY APPLICATION OF CHEESE WHEY IN SITU: A CASE STUDY WITH FIELD, CHEMICAL AND MOLECULAR BIOLOGY ANALYSIS
Monika Stavělová
Iva Dolinová 2), Maria Brennerová 3)
1) AECOM CZ s.r.o., Trojska 92, 171 00, Prague, CZ
2) Technical University of Liberec, Studentska 1402/2, 46117,Liberec, CZ
3) Institute of Microbiology, AS ČR, v.v.i., Videnska 1083, 142 20 Prague, CR
Dehalogenation of the chlorinated ethenes (CE) to the non-toxic end-products ethane and ethene is the most efficient remediation technique - enhanced reductive dehalogenation (ERD). Remedial companies have over 50 year’s practical experience in the CE remediation. The competition among the remedial companies is enormous. The main efforts are focused to cost efficient monitoring, and reducing of time of remediation and remedial price. Nowadays, the requirements for final remediation are much more stringent, since the remedial limits are comparable with the criteria for lowest pollutant concentration several years ago. We still need to understand the transformation of CE depending on the geological environment, changes in oxidative-reductive conditions and microbial activity. Since the ERD is frequently halted to 1,2-dichloroethene (1,2-DCE) or to the carcinogenic vinyl chloride (VC), the interpretation of analytical data together with molecular biological analysis for present dechlorinating bacteria and reductive dehalogenase genes can be used for controlling of the remediation procedure. A model site is characterized using optimized methodology elaborated by the Institute of Microbiology (IM), Technical University of Liberec (TUL) and the technical part of the project team - AECOM CZ (AE). Groundwater (GW) samples were collected in dynamic state using Micro purging methodology up to the hydrochemical parameters stabilization point (pH, redox-potential, conductivity). The collected samples were analyzed by accredited laboratory for: CE content including VC, organic substrate content using COD, CH4, ethane, ethylene, H2S+S2-, SO42-, PO43-, NO3-, NO2-, NH4+, Fe2+, Mn2+, Sr and K+. Attention was paid to minimization of exposure of all samples to oxygen. In situ anaerobic reactor management – AE: In advance, a baseline of the contaminated site was determined for the complete range of field measurements, laboratory and molecular genetic tests. Cheese whey was then repeatedly injected into the wells containing chloroetenes at intervals of several months. The amount of cheese whey applied to each well was depended on the progress of contaminant transformation. The primary contaminants PCE and TCE were nearly completely transformed to 1,2-cis DCE, and VC started to accumulate, thus, indicating transformation to the nontoxic final products. Molecular-genetic analyses - IM: A main result of the cooperation includes optimization of the DNA extraction from the GW and soil samples using an advanced automated laboratory tool - MaxwellTM 16 System: filtration of 3-5 liters of GW through 0,2 µm nylon membrane, preextraction of DNA, and isolation of DNA in the automated device. Detection of key bacterial species involved in the respiration of CE, and genes (vcrA a bvcA) coding reductive dehalogenases, enzymes crucial for the dehalorespiration pathways (transforming PCE →TCE→ DCE→VC→ ethylene) was carried out using polymerase chain reaction (PCR) method. Primer sets targeting Dehalobacter sp., Dehalococcoides sp., Geobacter sp., Sulfurospirillum sp., Desulfitobacterium sp. Additionally, the presence of sulphate-reducing bacteria was monitored, thus, indicating any changes of the in-situ oxidation-reductive conditions during remediation. Nanosamplers – TUL: An alternative approach for acquiring DNA from groundwater is tested using stationary samplers containing nanofiber components. An optimal way of DNA/RNA stabilization during transport from site to laboratory had been examined. Detection of ERD key bacterial species and vcrA a bvcA was made and compared with the results from continual monitoring of the groundwater during the remediation activities.
This research is co-financed by Technology Agency of the Czech Republic, project Techtool (TA0202534).
The increasing presence of organic micropollutants in different segments of the water cycle poses a serious threat to future water resources. These micropollutants are currently being detected at low concentrations in groundwater and surface water used for drinking water. Current monitoring (chemical analyses) gives an indication of the presence of these micropollutants. However, little is known about natural attenuation, that is processes that contribute to removal of micropollutants under in situ conditions. This information is required to assess and predict the long term risks of contamination of drinking water intakes.
Natural attenuation of pesticides in the subsurface is an important process that protects groundwater resources from these organic micropollutants. However, in order to properly rely on natural attenuation, information on biodegradation rates and tools for assessing degradation capacity are required. While biodegradation of many of the pesticides currently found in monitoring wells has been researched, often these studies have been performed under optimized laboratory conditions. The results from such experiments, including degradation rates, pathways, and molecular markers for assessing biodegradation, can thus not be easily translated to describe degradation under in situ conditions.
The work presented here is a step towards developing an understanding of natural attenuation under in situ conditions in the subsurface. A multi-disciplinary approach is taken, whereby information on contaminant degradation, subsurface geochemistry, and microbial community structure are integrated into a thorough understanding of the environmental conditions associated with natural attenuation. To this end, laboratory degradation experiments as well as field measurements are performed. In addition to determining degradation rates under various environmental conditions, molecular tools are also applied in order to characterize the microbial populations required for biodegradation. This work is thus a step towards understanding degradation under in situ environmental conditions and developing molecular based tools for monitoring degradation capacity. Together, these results provide valuable information on the natural attenuation of pesticides in subsurface systems.
In-situ bioremediation is a commonly used remediation technology to clean up the subsurface of an organic-contaminated site. The process of in-situ bioremediation involves complex and uncertain relationships among biomass, contaminant, nutrients, and appropriate control actions. This study discusses the development of a simulation model-based, dynamic, and multi-objective to support the control action for a bioremediation site, which involves substantial complex and uncertain data.
To investigate remediation performances, a subsurface model was employed to simulate contaminant reactive transport. In a complex geochemistry which involves different organics compounds the interactions among the system components are difficult to understand, and it is practically impossible to accurately predict potential subsurface reactions. In the first step, a reactive transport model was formulated to evaluate and decrease the uncertainties about the sources terms. In the second step, the knowledge provide by the model can be acquired and incorporated in a predictive model to optimize the control action of the remediation process. The developed system has been applied on real site data. Application of the proposed approach to a bioremediation process in a real site, which involves substantial uncertain data on the sources terms, indicated that it was effective to understand a complex geochemistry and to provide support in real-time process control of the in-situ bioremediation systems.
The proposed in-situ bioremediation process optimization is done through the application of common groundwater flow and reactive transport models (MODFLOW, MT3DMS, PHT3D) to provide to modelers and decision maker with a cost effective tool which is transferable from the present study to other site managed by in-situ bioremediation.
At several sites in the Netherlands Bioclear stimulated biological degradation of volatile organic chlorinated compounds (VOC) successfully. The technique used is based on direct injection of carbon source and, if needed additional specific dechlorinating bacteria Dehalococcoides spp. (DHC). This technique is, instead of most in situ remediation techniques, very well applicable in poorly permeable soils like clay and peat. Direct push injections are typically used to remediate a source zone. Research and field experience have shown that chlorinated ethenes concentrations close to the maximum solubility can be biologically degraded.
Direct injections are performed with a small injection machine. Protamylasse can be used as carbon source. Protamylasse does not only contain organic carbon but contains also enough nutrients for the growth of dechlorinating bacteria. Protamylasse is an organic waste stream from the potato starch industry. Which is an environmentally friendly (and cheaper) alternative compared to chemically produced carbon sources like lactate, acetate or hydrogen release compound. If injection of dechlorinating bacteria is desired, a culture with a high concentration of dechlorinating bacteria is obtained from a lab.
A distance between the injection points of 1 to 3 meters is used to ensure appropriate distribution of the additions. Not only soils consisting of sand but also low permeable soils like peat and clay can be remediated with this technique. Depending on the type of soil, injection can be performed to around 30 m-bgl. Because the injection machine is relatively small, injection can be performed in hard-to-reach urban locations. Injection at an angle of 45 degrees makes it possible to inject under buildings. Injection takes typically one to three weeks, depending on the size of the project. After the injections, the ‘passive phase’ starts. During the passive phase the degradation of chlorinated ethenes will take place and can be monitored.
In this presentation 5 different examples will be given of locations that were succesfully treated by means of direct injections. Concentration of contaminants varies to a maximum of 140,000 µg/l DCE. Different soil types were treated with this technique. In the presentation we will also focus on the remediation results, time, costs and sustainability.
Background and Objectives. Emulsified vegetable oil (EVO) applications to support anaerobic
bioremediation can be advantageous from a cost basis in that a long-lasting organic carbon
source can be delivered to the subsurface during infrequent injection events. Because these
applications may serve as the sole form of remedial activity over a several year period,
understanding the EVO distribution achieved and the resulting concentration of dissolved
organic carbon (DOC) that can be sustained and available for microbial use is critical to
successful design. To date, EVO loading rates (injected concentration) and distribution extent
(droplet transport) have generally been defined by stoichiometric electron donor calculation or laboratory-derived oil to soil loading ratios. Results from multiple field efforts indicate that these projections can significantly underestimate the required EVO loading and these values must be evaluated on a case-by-case basis to confirm droplet retention (adherence or straining) and provide sufficient organic carbon distribution for treatment within the targeted area.
Approach/Activities. Using fluorescent dye tracers and the combination of both total and
dissolved organic carbon fractions, pilot and full-scale EVO injection applications have been
conducted at numerous sites to evaluate differences between multiple EVO substrates, injection techniques (direct push and permanent wells), and overall treatment strategy (grid-style points or treatment barrier) to further refine EVO application design. Results from these activities indicate that the extent of EVO droplet straining can be more than one order of magnitude higher than that predicted based on current literature values. This can result in insufficient distribution of EVO and DOC following injection and limit overall treatment performance and remedial success. In addition to droplet straining behavior, differences in both dye tracer and organic carbon wash out have been used to characterize DOC strength and groundwater residence time within multiple injection areas. Coupled with volatile organic compound (VOC) treatment data, these wash out rates can help determine the required residence time for optimal system design.
Results/Lessons Learned. A summary of the EVO droplet straining behavior and extent
observed at multiple field sites will be presented and will be coupled with a detailed case study to illustrate the key design considerations for practitioners applying EVO. The case study results include dose response data (tracer dye and EVO transport characterization) used to confirm droplet retention at monitoring wells within the radial extent of injection; and results of a method of moments approach used to evaluate the groundwater velocity within two different hydrostratigraphies (fine sand and gravelly sand) to illustrate differences in droplet distribution, achievable DOC concentrations, and groundwater residence time through the EVO injection area. These data were then correlated with the VOC treatment performance achieved. Results indicate that the groundwater velocity between the two units varied by two-fold (0.07 m/day versus 0.14 m/day), which resulted in differences in sustained DOC (273 milligrams per liter [mg/L] versus 155 mg/L, respectively) and the overall extent of chlorinated VOC treatment over a nine-month time period (reduction of 95% versus 45%, respectively).
Background/Objectives.
1,4-dioxane is an emerging contaminant found in groundwater at sites throughout the United States. Historically used as a stabilizer for chlorinated solvents and hence routinely detected at chlorinated impacted sites. It’s known for being highly mobile and recalcitrant to typical remedial applications that rely on volatilization and biodegradation due to its physical and chemical properties. In-situ chemical oxidation (ISCO) is a promising alternative to pump and treat applications using ex-situ advanced oxidation processes. Selecting a suitable ISCO strategy for in situ remediation of both 1,4-dioxane and associated co-contaminants can be challenging and may vary with site-specific geology and geochemistry. To inform the design of full-scale remediation, ARCADIS conducted treatability studies using groundwater impacted by 1,4-dioxane and co-contaminants from two sites with different geological settings (bedrock and heterogeneous sands and silts). The objectives of the treatability tests were to evaluate the efficacy of treatment using sodium persulfate under multiple activation strategies, determine the most effective activator, and approximate the oxidant and activator dosing requirements for field-scale application.
Approach/Activities.
ISCO treatability studies were conducted in a similar manner at two sites with different geochemical environments (gneiss bedrock and heterogeneous silts/clays/sands). Groundwater with either soil or crushed rock were treated with up to 50 g/L sodium persulfate in both tests. The testing included control samples, ambient (no activation), chelated iron, and alkaline (sodium hydroxide) activations to generate the free radical reaction mechanisms. Multiple phases of treatability studies were conducted to determine optimal ratios of activator and oxidant at each site. Byproducts of the reactions, including dissolved metals, acetone and chlorinated methanes and ethanes were measured as part of the study. The overall effectiveness of the oxidant and chelators were evaluated, including the effectiveness of 1,4-dioxane treatment, co-contaminant destruction, and the magnitude of metal mobilization and chlorinated byproduct production.
Results/Lessons Learned.
The results of the treatability studies show that 1,4-dioxane can be successfully eliminated with sodium persulfate using multiple activation mechanisms. Despite different geochemical environments, sodium hydroxide-activated sodium persulfate treatments demonstrated the most promising results at both sites. A 4:1 molar ratio of sodium hydroxide to sodium persulfate was observed to be most effective in treating 1,4-dioxane and co-contaminants while minimizing byproducts. The results of the treatability tests demonstrate that multiple activation methods are capable of near complete destruction of 1,4-dioxane and that specific site geochemistry impacts the removal efficiency and rate of byproduct formation. Preliminary data from field applications at each site utilizing activated sodium persulfate with sodium hydroxide will also be presented.
Collectively, ARCADIS has conducted over 150 independent treatability tests for remediation via in situ chemical oxidation (ISCO) across our global remediation network. The results from treatability testing were used select site-specific remedies and activation chemistries for both common and emerging contaminants. This presentation will present an analysis of the dataset generated from this large suite of testing and summarize the key lessons learned for ISCO reagent and activator selection and field implementation, including:
• Potential oxidant-contaminant interactions
• Oxidant demand based on contaminant type and mass
• Soil oxidant demand from organic carbon, reduced metals, and anions
• Aquifer characteristics (i.e. groundwater flow velocity) and activation kinetics
In addition, the effects of different activation approaches, such as alkaline desorption/surfactant effects and generation of organic intermediates from the oxidation of certain contaminants will be discussed. This information gleaned from treatability testing and implementation supports the existing literature pertaining to what techniques work best and provides information where there are gaps in the current literature.
In situ chemical oxidation (ISCO) is an effective technology for clean up site contaminated by organic compounds. This remediation involves the introduction of a chemical oxidant into the subsurface for the purpose of transforming groundwater or soil contaminants into less harmful chemical species. Commonly applied oxidants are permanganate, hydrogen peroxide (with or without iron), ozone and persulfate.
For ISCO to be effective, the oxidant must contact the contaminant. This can be difficult in many soils and aquifers where natural heterogeneities can result in flow bypassing around lower permeability zones or where the presence of natural compounds can generate non-productive reactions that consume oxidant compromising the adequate oxidant transport and distribution.
Environmental conditions and site characterization have to be taking into account in order to optimize the ISCO application. A few studies have been carried out in saltmarsh areas under Mediterranean climate conditions. This work has been developed in Southern Spain in an 1.5 ha site where several hydrocarbon leakage from ancient fuel storage tanks and transport facilities have been reported. The working area is a complex site with a substrate consisting of irregularly distributed anthropic deposits over marsh sediments, usually clayey; both anthro- pogenic and natural marsh deposits show a remarkable heterogeneity in their morphological and physicochemical properties. The work area presents a water table with high spatial and temporal variability, in a context of a Mediterranean climate with mild and wet winters and warm and dry summers. In such conditions, a large number of prospections have been performed in order to assess the type of materials present, its thickness and its spatial distribution. This activity, carried out with pedological criteria, has enabled to define horizons or levels where initial physicochemical and morphological characterizations is needed. In parallel, groundwater sampling has been carried out by establishing a network of monitoring wells, which allowed the initial hydrochemical characterization of the site and the establishment of groundwater levels, which were subsequently monitored. After a preliminary laboratory and pilot tests, ISCO was applied in the working area.
Hydrogeochemical characteristics (basic pH and high carbonate, sulphate and chloride concentration) involved the use of iron chelates to keep the iron in solution and to increase peroxide lifetime. Hydraulic characteristics (low permeability of shell level, possible preferential pathways – anthropogenic fill with more permeability – and shallow depth of groundwater) determined well construction, well layout, delivery strategy and injections sequence. Regarding injection strategy, 36 wells were perforated and a total of 14,000 L of pressurized hydrogen peroxide and catalyst solution with iron and hydrogen peroxide stabilizer were injected separately to increase the radius of influence. Taking into account hydrogeological characteristic of the site and the gas generation due to reagent injection, the injection flow were less than 1 L/min to avoid high pressure that besides might generate surfacing.
Preliminary results indicate the efficiency of the experimental design under the adverse conditions of the site (heterogeneous hydraulic conditions, low permeability and the elevated presence of scavengers). A general TPHs contamination reduction in 80% of the wells closed to 57%. This validation of the design allows to optimize the ISCO treatment, currently carried out, in the working area in order to reduce the contamination according to the project objectives.
This work has been performed within the framework of the BIOXISOIL (LIFE 11 ENV/ES/505) project funded by the EU through the LIFE Programme.
Fe-containing zeolites are a promising material for the removal of organic contaminants from groundwater, since they can be tailored for an optimal combination of two functions: I) Zeolites with appropriate channel structure and SiO2/Al2O3 ratio have excellent adsorption efficiencies for small organic molecules such as MTBE, BTEX or chlorinated solvents. II) The ion exchange sites located in the pore channels and cages of zeolites allow dispersion and stabilization of isolated iron ions, which are highly active in redox reactions. Thus, Fe-loaded zeolites have been shown to function as heterogeneous Fenton-like catalysts over a wide pH range including neutral conditions [1-3].
With respect to ex-situ treatment of contaminated groundwater, Fe-zeolites can be an interesting alternative to activated carbon since Fe-zeolite adsorbers offer the option of easy on-site regeneration by flushing with H2O2 solution [1].
In the framework of the EU project NanoRem a novel concept for in-situ chemical oxidation based on the application of colloidal Fe-zeolites is developed. The basic idea is to apply a solid adsorbent and catalyst for Fenton-like oxidation in the form of a suspension, which can be injected into the aquifer in an initial step, separate from the subsequent addition of H2O2. The colloidal particles are transported over a certain distance and deposited on the aquifer sediment, where they form an active zone in the preferred groundwater flow paths. Using a stationary solid catalyst has the advantage to allow a mixing with the oxidant in the subsurface, i.e. at the location of the contamination. By this means, the injection of mixtures of catalyst and H2O2, causing vigorous reactions and thus safety issues known from conventional Fenton-based ISCO, could be avoided. In addition, prior to oxidant injection the Fe-zeolite zone could be initially used as a sorption barrier. By this means aqueous phase concentrations of contaminants are reduced and further spreading of plumes is prevented. At the same time, the sorption barrier can enrich contaminants from a larger volume of water before injecting the oxidant into it. This would correspond to an increased radius of influence of the ISCO process and a more efficient utilization of H2O2.
This contribution summarizes results from lab experiments on the selection and optimization of Fe-zeolites with respect to transport and distribution in saturated porous media as well as adsorption and catalytic oxidation of various groundwater contaminants (MTBE, trichloroethene (TCE), 1,2-dichloroethane (DCA) and toluene). Structure-property correlations were derived by screening various zeolite types differing in framework type and SiO2/Al2O3 ratio for adsorption of model contaminants. Channel diameter (determined by the framework type) and surface hydrophobicity (determined by SiO2/Al2O3 ratio) are the most influential factors in this process. Even though high-silica zeolites have a low ion-exchange capacity and thus can take up only limited amounts of iron ions, it was possible to obtain sufficiently active catalysts for oxidation of adsorbed contaminants by H2O2 [3].
Soluble (modified) biopolymers were applied in order to obtain appropriate suspension stability and transport properties of the colloidal zeolites. Due to the fact that these soluble polymers are excluded from the inner pore volume of the zeolites by virtue of their size, no significant adverse effects on contaminant adsorption and catalytic performance of the Fe-zeolites are observed.
Particle mobility was studied in 1D-column experiments using standard materials (porous media and water) and protocols developed in the NanoRem project. For stabilized Fe-BEA-35 (the first prototype Fe-zeolite selected), promising results on mobility were obtained, showing breakthrough of 85% particle mass concentration from a 20 cm column (washed quartz sand 0.3 - 0.8 mm, soft water, u = 10 m/d, cparticle,in = 1 g/L, cstabilizer = 1.5 g/L).
In batch experiments Fe-BEA showed high catalytic activity in Fenton-like oxidation even in very hard water (pH 8.2). Reaction rates of the model contaminants were increasing in the order DCA < MTBE < TCE < toluene, which is in accordance with the selectivity predicted for a reaction driven by OH-radicals.
In addition, column experiments simulating the cycle of catalyst infiltration and immobilization, contaminant adsorption and degradation were conducted using MTBE as model contaminant. Fe-BEA-35 which was loaded on washed quartz sand at a mass fraction of 1 wt% showed stable adsorption and catalytic properties over three cycles of infiltration of MTBE-contaminated water (10 mg/L MTBE in very hard water, u = 1 m/d) with intermittent regeneration by H2O2 infiltration (10 g/L H2O2 in very hard water, u = 1 m/d).
Acknowledgements: This work was supported by funding from European Union within the NanoRem project.
[1] A. Georgi, R. Gonzalez-Olmos, R. Köhler, F.-D. Kopinke, Separation Science and Technology, 45 (2010) 1579.
[2] R. Gonzalez-Olmos, F. Holzer, F.-D. Kopinke, A. Georgi, Applied Catalysis A: General, 398 (2011), 44.
[3] R. Gonzalez-Olmos, K. Mackenzie, F.-D. Kopinke, A. Georgi, Environmental Science and Technology, 47 (2013), 2353.
OPTIMUM HYDROCARBON TECHNOLOGIES (OHT) is developing a new and innovative technology (later referred to as “the OHT process”) to extract hydrocarbons from polluted soils & water.
The OHT process uses a polymeric material (the agent) which is hydrophobic, oleophilic and capable of reversibly adsorbing hydrocarbons.
The hydrocarbons are selectively transferred from their matrix onto the agent in a mixing/adsorption vessel and can then be recovered from the oil-rich agent. The desorbed agent can then be reused in additional process cycles. The process operates at ambient temperature.
This presentation recalls the main principles of this innovative technology and highlights the latest results of this research program. It also summarizes the numerous possible applications of this technology, ranging from the remediation of hydrocarbon polluted soils to the production of oil from oil sands and including the treatment of the effluent waters produced by the petroleum industry.
Remediation of a tar related contamination: watercourse in agricultural area
Debeuf A.1, Mulders S.²
1 OVAM, Stationsstraat 110, 2800 Mechelen, Belgium, P: +32 15 284 531, F: +32 15 284 408, adebeuf@ovam.be
2 Tractebel Engineering, Arianelaan 7, 1200 Brussel, Belgium, P: +32 2 773 99 11, F: + 32 2 773 99 00, info@technum-tractebel.be
Topic: Excavation and ex-situ treatment of contaminated watercourse in agricultural area: remediation targets, practical approach and difficulties during implementation
Willebroek-Noord (120 ha) is an obsolete industrial area situated between Antwerp and Brussels. Despite its excellent strategic location, about 50 ha have been unused during the last decades. The existing soil contamination and residual waste materials complicate the redevelopment of this area. From a former gas plant, situated in the southern part of Willebroek-Noord, tar-containing wastewater was until 1978 drained in the Gorrebroekloop, a small watercourse that partially flows through agricultural area. Over time the tar-contaminants (mainly benzene, PAH’s and mineral oil) have been spread from the sludge layer into the underlying sediments and aquifers. Due to flooding and sludge deposits on the banks the topsoil of the nearby agricultural land has also been contaminated.
This first remediation phase provides in the removal of the topsoil (because of the human-toxicological risk for agricultural use), the highly contaminated sludge and a maximum amount of heavily contaminated subsoil to approximately 2 m below ground level (to prevent the spreading of pollution through surface water).
A total amount of about 60.000 tons was excavated and transported for ex-situ remediation. After the filling up with clean soil the watercourse was reshaped. To protect the banks against erosion biodegradable coconut mattings were used.
During a second phase the deeper contamination (to 15 m below ground level) will be remediated with in-situ techniques.
The following challenges made of this at first sight simple but large-scale excavation an interesting and instructive project:
- The site was inaccessible for heavy traffic that was needed for the excavation and transportation of the tons of soil. Along the entire watercourse (about 600 m) topsoil was removed and a temporarily 7 m wide road was constructed with a package of 50 cm crushed stones.
- It was necessary to keep the farmers well informed before and during the remediation, because part of their land was temporarily unavailable. The farmers were paid a fee for structural damage of the soil and for the loss of a part of their crop.
- A high pressure oxygen pipe that crosses the watercourse at a shallow depth, a gas pipeline and a high tension line pylon right along the excavation made some adjustments and extra safety regulations during the works necessary.
- To reduce the odour nuisance for the residents several extra measures were considered. A rotary atomizer was constantly available on the site. PID measurements were done to check the volatile organic compounds.
Preference: poster presentation
At the former low temperature carbonization plant „Schwelerei Deuben“, massive soil and groundwater contaminations are caused by residual and free oil phase (LNAPL) which have a lasting adverse effect on the groundwater especially with phenols, BTEX, PAH and ammonium.
The LNAPL reached the site boundary as mobile local floating and incoherent blobs. The contaminant plume in the groundwater has exceeded the boundary significantly. A conventional pump & treat system with a hydraulic supported oil skimming effectively prevents the further propagation of the groundwater contamination.
The mid-term remediation strategy is to achieve a stationary groundwater plume without further contaminant migration applying enhanced natural attenuation. To reach this goal stepwise, innovative remediation technologies for enhanced oil recovery (EOR) have been tested to optimize the site remediation strategy and to enable site specific permissions for the technology application by the authorities.
Two pilot tests for the EOR-remediation are implemented by the in-situ technologies mobilizing solvent soil flushing (solvent: 100% n-butanol) in sandy layers and in-situ thermal treatment with thermal wells (THERIS method) in silty, loamy formations. Both methods complement regarding the hydrogeological boundary conditions. Required values have been achieved during the pilot field tests demonstrating the efficiency of the applied EOR methods. Design and conduction of both methods have been confirmed technically and legally within an acceptable time and cost expenditure:
• significant reduction of residual oil phase and its harmful effect (contaminant emissions) from the unsaturated zone,
• recovery or immobilization of mobile oil phase from the unsaturated and the saturated zone,
• stimulation of an efficient aerobic in-situ degradation of the remaining contaminant mass flux in the groundwater as a permanent ENA-process.
Process-related objective of mobilizing solvent soil flushing is to convert moderate mobile oil-phase into a swelling oily mobile phase by infiltration and spreading of n-butanol as a solvent fluid at the capillary fringe zone increasing this way the relative permeability. The mobile phase is recovered at wells as much as possible (preliminary remediation). In a second step, the resting ratio of butanol in the residual oily phase and in the groundwater has to be reducted by intensive water flushing. Finally, aerobic in-situ degradation of dissolved butanol and dissolved contaminants has to be stimulated by the injection of oxygen gas.
Process-related objective of the thermally EOR-THERIS is the mobilization of residual oil phase by reducing viscosity and surface tension due to increased subsurface temperature
Mobile oil phase was recovered by a multi-phase fluid pump and skimming, soil vapour extraction avoided an uncontrolled migration of volatile compounds like BTEX. Significant thermally enhanced oil phase mobilization could be observed by reaching temperatures at and above approximately 70°C in large areas of the pilot test.
Since 2013, both EOR techniques have been proved in pilot test areas of approximate 100 m², embedded into the continued pump & treat system.
The pilot tests at the former low temperature carbonization plant Deuben take place by order of the Lausitzer und Mitteldeutsche Bergbauverwaltungsgesellschaft mbH, and are coordinated and managed by GFI Dresden.
The Fenton Process is based on the production of the highly reactive hydroxyl radical (OH•), which is resulting from the reaction between hydrogen peroxide (H2O2) and ferrous ions Fe(II) under acidic conditions. The oxidation system, which relies on Fenton’s reagent, can be employed to treat various types of waters and wastewaters containing a range of organic pollutants like phenols, polycyclic aromatic hydrocarbons, pesticides, formaldehyde, wood preservatives, plastic additives and rubber chemicals. The treatment of polluted waters using Fenton process results in reduction of toxicity, improvement in biodegradability, odour and colour removal. The Fenton process can also be employed as a post- or a pre-treatment step in the treatment of high strength polluted waters with extremely toxic and refractory nature. In the Fenton process, iron and hydrogen peroxide are the two major chemicals that determine not only the operation costs but also the treatment efficacy (Zhang et al., 2009). The objective of the present investigation was to examine the effectiveness of Fenton Process in treating polluted waters of different origins. The performance of Fenton oxidation employed in the treatment of soil washing solution, landfill leachate and phenolic water was investigated with an aim of determining their optimum reaction conditions. For this purpose, all experiments were performed in the batch system. The influence of H2O2, FeSO4 concentrations and reaction time on the removal efficiency were investigated. The pH of reaction mixture was adjusted at the start of the reaction. Required amounts of FeSO4 and H2O2 were added simultaneously into the solution and then the mixture was shaken using a mechanical shaker. The progress of reaction was followed by monitoring the disappearance of the contaminant and chemical oxygen demand (COD). The results indicated that the Fenton process was successful in the treatment of polluted waters. Organic pollutants (e.g. phenol, fluorene, etc) were efficiently removed by the Fenton process. Removal efficiency depended on the reaction time and Fe(II) and H2O2 concentrations. 83% of phenol was degraded and 60% of COD was removed at conditions of H2O2 500 mg/L, Fe2+ 30 mg/L, phenol 250 mg/L and pH 3.0. Similarly, in the treatment of soil washing solution 40% of COD was removed under optimum conditions, which were 2 hours reaction time, 2% H2O2 concentration and 1/50 Fe/H2O2 ratio. In the treatment of landfill leachate, a COD removal of 66% was obtained for 5000 mg/L hydrogen peroxide and 30 min reaction time.
Keywords: polluted waters, Fenton process, system optimisation
1C.5 - Miscellaneous
2. Soil, groundwater and sediment in the biobased, circular economy
3. Managing multiple functions of the subsurface
4. The role of the subsurface in climate change adaptation
EFFECTS OF PLANT GROWTH PROMOTING MICROORGANISMS ON WHEAT PLANT GROWTH AND AMINO ACID CONTENT
Metin Turan1, Fikrettin Şahin1 Nurgül Kıtır1 , Adem Güneş2 ,Medine Güllüce3, Güleray Ağar3,Hatice Öğütcü4
1 Department of Genetic and Bioengineering, Faculty of Engineering and Architecture, Yeditepe University, Istanbul, Turkey
2 Erciyes University, Faculty of Agriculture, Department of Soil Science, Kayseri, Turkey
3Atatürk University, Department of Biology,Erzurum,Turkey
4Ahi Evran University, Department of Biology, Kırşehir, Turkey
This study was conducted on aridisols, a soil ordo widely existing in Turkey’s Eastern Anatolia Region. A greenhouse trial on wheat was conducted in 45 pots with an experimental design of 9x5 factorial, including a control and 8 microorganisms (Bacillus megaterium M3, Bacillus subtilis OSU-142, Bacillus pumilus C26, Paenibacillus polymxa, Azospirillum brasilense Sp-245, Burkholderia cepacia BA-7, Burkholderia cepacia AMR-BA7, Raoutella terrigena). Plant and soil samples were taken at the end of the growth period (90 days). Macro- and micronutrients from soil samples and plant roots were determined along with amino acids, enzymes, ureas, dehydrogenase, acid, alkali phosphates, catalase (CAT), peroxidase (POD) and super oxide dismutase (SOD). The results showed that amino acids, plant and soil enzymes extracted from root parts significantly affect wheat plant growth. The highest wheat dry matter was obtained with the Bacillus subtilis OSU-142 PGPR application. However, application of PGPR decreased amino acids extracted from plant roots. The lowest extracted amino acid was obtained with the Paenibacillus polymxa PGPR. Positive correlations were determined between the PGPR and wheat plant nutrition/dry matter. On the contrary, extracted amino acids had negative correlations with the PGPR application. The plant enzymes such as catalase (CAT), peroxidase (POD) and super oxide dismutase (SOD) increased following the PGPR application and the highest values were obtained with the application of Paenibacillus polymxa PGPR.
Keywords: PGPR, Wheat, Plant enzymes.
Background/Objectives.
Currently there are far fewer technologies available for treating metals impacts in groundwater in-situ than there are for treating organic contaminants. This relates to the fact that unlike organics, metals cannot be biologically degraded or be easily driven into a vapor phase to enhance their recovery. Effective in-situ treatment methods for arsenic stabilization offer a number of benefits over removal/recovery-based methods, but require careful consideration of mechanisms and longevity.
A patent-pending method for the in-situ removal of arsenic from groundwater will be introduced. The method facilitates the delivery and distribution of iron in a fully soluble form, followed by the formation of ferric iron oxyhydroxide precipitates that can remove arsenic from groundwater and retain it via co-precipitation. Thus far, distribution of iron has been limited due to iron particle size, solubility, and/or transport in the groundwater. Success has been achieved relying on shallow trenches for emplacement of reactive iron materials, but limited solutions have been developed for deep aquifers. The treatment approach provides a means to solve the historic challenge of effectively delivering and distributing iron in the subsurface. The end result is the creation of beneficial minerals that will not only retain the arsenic but remain stable in naturally aerobic and neutral aquifers, lending permanence and sustainability to the outcome. The approach can be tailored to site specific geochemical conditions, and may be designed to yield excess sorptive capacity/remediation potential to provide passive treatment of residual contaminant mass beyond the initial treatment event.
Approach/Activities.
Data will be presented from both a field site in Alaska, and laboratory testing completed to refine the approach. Results from the laboratory trials will include both jar and column tests to prove the reaction mechanism concepts and the ability to distribute iron without compromising permeability. Jar tests conducted in soil/groundwater slurries show removal of arsenic with addition of iron, acid, chelant and oxidant. Columns were prepared with site soil and groundwater, adding groundwater impacted with 1400 ug/L of arsenic. An injection test at a site in Alaska was also conducted, showing removal of more than 400 ug/L from monitoring wells within the influence of the injection.
Results/Lessons Learned.
Using this method, treatability studies have shown removal of over 1400 ug/L of arsenic is feasible. Injections at a field site in Alaska have demonstrated removal of 400 ug/L Arsenic impacts without loss of permeability in the aquifer. The results of bench and pilot scale-proof of concept studies will be presented in order to explain the theory driving this method and illustrate how this treatment method can be developed and applied at sites where elevated arsenic concentrations are observed. Additional laboratory trials conducted in the winter of 2013 will be available. Results from a planned for the winter of 2014 field trial may also be available.
The local municipality has conceptual redevelopment plans for a former manufactured gas plant (MGP) which have accelerated plans for full-scale cleanup. Located along a river used for shipping goods, the site is impacted with MGP DNAPL and LNAPL over approximately 0.80 acres within a sandy (dune) aquifer. The DNAPL exists between approximately 35 to 40 feet below grade and is present in river sediment. An air sparging fence is currently in operation to prevent exceedances of petroleum compounds associated with the LNAPL from entering the river.
ARCADIS and Savron are piloting the Self-Sustaining Treatment for Active Remediation (STAR) technology for remediation of both the LNAPL and DNAPL in November 2014. This is the first site where STAR will be applied to both LNAPL and DNAPL in the same unconfined aquifer. In situ stabilization/solidification (ISS) and in situ smoldering combustion technology are being evaluated for full-scale remedy, the latter of which has the potential to save the client approximately $1.5 million in remedial costs. The required design criteria and cost range are fairly well understood for the ISS remedy; however, the STAR technology has not yet been implemented full-scale at an MGP Site. Therefore, the STAR pilot test is being conducted to provide treatment verification and to provide critical design data such as radius of influence (ROI) and propagation rate which are the primary cost drivers for full-scale implementation, providing additional confidence to the full-scale cost comparison between ISS and STAR.
The expected data set will include operational parameters (temperature profiles in the subsurface at multiple radial distances and depths, VOC and CO/CO2 content of the vapor discharge, perimeter air monitoring results), as well as pre- and post-pilot test soil samples for TPH analysis. A discussion on best practices for ROI consideration and cost implications/ranges will be provided.
Soil pollution by hydrocarbons is a worldwide environmental concern. Among this class of pollutants, 37% of the French sites are contaminated by total petroleum hydrocarbons (TPH). Their impact on human health and environment is well known because of their hydrophobic characteristics permitting them to reach and accumulate in the food chain. They are indeed likely to cause toxic effects to human and environmental receptors. Furthermore this toxicity is closely related to their structures. Their physical and chemical properties such as solubility and Kow favour their accumulation in organic matter and human bodies via food chain. Furthermore, soil as well as groundwater quality are endangered by the accumulation of TPH.
Biological, physical and chemical in situ treatment methods are often used but these techniques are very often time-consuming and require high engineering costs. Besides, before implementing an in situ soil treatment technique at full-scale, laboratory tests should be performed in order to adapt the technique to the field conditions. As a consequence, ex situ techniques such as soil washing are getting more and more interest despite that soil excavation is necessary. Since 2007, French policy on polluted sites is strongly oriented towards the use and operation of in situ treatment methods. In situ treatment of TPH contaminated soils could be achieved by soil flushing. However, this remediation approach is still being developed by companies as it does not require soils excavation, allowing this technique still to be more cost-effective than ex situ processes. Surfactants are chemical compounds frequently used for the extraction of hydrocarbons from soil.
Although this washing technique is generally efficient to clean soil, the major concern remains in the treatment of the leachates containing both TPH and surfactants. Such solutions contain a significant amount of hard COD, which require an advanced oxidation treatment to be degraded. Electrochemical Advanced Oxidation Processes (EAOPs) have shown promising results to treat many poorly biodegradable organic compounds in solutions .
In order to improve the efficiency of soil washing treatment of hydrocarbon contaminated soils, an innovative combination of this soil treatment technique with an electrochemical advanced oxidation process (i.e. electro-Fenton (EF)) has been proposed.
An ex situ soil column washing experiment was performed on a genuinely diesel-contaminated soil. The washing solution was enriched with Tween® 80 at different concentrations, higher than the critical micellar concentration (CMC). The impact of soil washing was evaluated on the hydrocarbons concentration in the leachates collected at the bottom of the soil columns. These eluates were then studied for their degradation potential by EF treatment.
Results showed that a concentration of 5% of Tween® 80 was required to enhance hydrocarbons extraction from the soil. With this Tween® 80 concentration, the efficiency of the treatment was only about 1% after 24 h of washing. Electrochemical treatments performed thereafter with EF on the collected eluates revealed that the quasi-complete mineralization (> 99.5%) of the hydrocarbons was achieved within 32 h according to a linear kinetic trend. Toxicity was higher than in the initial solution and reached 95% of inhibition of Vibrio fischeri bacteria measured by Microtox® method, demonstrating the presence of remaining toxic compounds even after the complete degradation. Finally, the biodegradability (BOD5/COD ratio) reached a maximum of 20% after 20 h of EF treatment, which is not enough to implement a combination with a biological treatment process.
This work showed that Tween® 80 was able to extract the heaviest hydrocarbons fractions from a highly contaminated soil. Moreover, great biodegradability enhancement is observed by using EF treatment even if toxic compounds still remain in the eluates.
Perflourooctane sulfonate (PFOS) and perflouroctanoic acid (PFOA) are emerging as contaminats of concern in many countries and authorities around the world have recently establised regulatory limits for groundwater. However, there are many other perfluorinated compounds (PFCs) and precursors of PFOS and PFOA found in aqueous film forming foam (AFFF) which is often comprises the source of the PFCs. Therefore, there are analytical challenges to overcome when considering how to assess soil and groundwater contaminated with PFCs as there are multiple analytes which can biotransfrom slowly to form PFOS and PFOA. Methods to overcome this analytical chaenge will be discussed and analytical site data presented to demonstrate how the analytical challenged can be best adressed.
This presentation will review the fate and transport charecteristics of PFOS, consider recent toxiclogical data.
Perflurourinted compounds are difficult to remediate in soil and groundwater systems due to their recalcitrant nature (i.e. are not amenable to icrbial biodegradation) and lack of volatility, therefore in situ remedial options are limited. Activated persulfate chemistry has been used effectively to treat soil and groundwater contaminated by a wide range of pollutants of concern.
Recent laboratory work has demonstrated that activated persulfate is capable of oxidizing perfluorinated compounds in groundwater but only when a specific activation method is employed, as with the smart combined oxidation and reduction (ScisoR®) technology. Laboratory data will show how this technology can deflourinated and hence mineralise both PFOS and PFOA. However, using ther methods of oxidation, such as Fenton’s reagent, to oxidise PFC from a site soil, an increased mass of PFOS ad PFOA is observed as the precursors are transformed to the dead end products of this oxidation reaction.
Laboratory results indicate that the ScisoR® technology capable of destroying PFCs derived from sote soil and groundwater and hurdles to be overcome before the next steps, which invove field implementation of an in situ project, are described. Remedial technologies, such as directed groundwater recirculation (DGR) to address the very long plumes of low concentrations of PFC’s will be discussed, with examples of how ARCADIS has successfuly remediated long plumes over short timeframes.
Background/Objectives. The presence of pesticides in soil and groundwater can pose a threat to human health and the environment. Pesticide contamination can occur as a result of accidental releases or intentional dumping at formulation and retail sites, misuse during application, or even through normal use. For example, in 1987, over 20 different pesticides were found in the groundwater of 24 states. In situ chemical oxidation (ISCO) has not been used extensively to treat these compounds because the nature of pesticide use commonly involves large, low-level aerial applications for which ISCO is not typically well-suited. However, where such compounds have been released to the environment as point sources or in areas where high concentrations are targeted for remediation, ISCO may be appropriate to consider as a remedial technology. The objectives of this presentation are to discuss the treatability of common pesticides using ISCO and to present data from laboratory evaluations of the treatability of pesticides such as lindane, chlordane, heptachlor, and chlorobenzenes using oxidants such as activated persulfate, catalyzed hydrogen peroxide (CHP), and ozone.
Approach. A review of the use of advanced oxidative processes for the treatment of pesticides will be presented. Substantial work has been conducted in the water/wastewater treatment industries (i.e. ex situ) to evaluate pesticides treatability using oxidants. This work has guided the limited work that has been done in assessing pesticides treatability in soil and groundwater using oxidants, either ex situ or in situ. Results of four treatability studies will be presented, where different oxidants (CHP, activated persulfate, or ozone) were applied to pesticide-contaminated field soils. The presentation will focus on the site-specific and design factors that influence the success of oxidative treatment of the pesticides lindane, chlordane, heptachlor, and chlorobenzenes. Although limited, intermediate and byproduct data for these studies will be presented as well.
Lessons Learned. Common pesticides are amenable to degradation using oxidants. The extent of degradation depends on site-specific characteristics, such as the degree of sorption onto soils, and the ability to maintain oxidative conditions (i.e., oxidant persistence). Intermediates and byproducts of pesticide oxidation have been observed and should be monitored during and after application of oxidants. While it is evident that pesticides can be degraded by oxidants, the viability of ISCO for treating pesticides sites will depend on the nature of the contamination – the mass distribution; the soil characteristics including particle size, total organic content, and groundwater geochemistry; the site’s hydrogeology; and, specifically, the aerial extent and depth of contamination.
Transport and deposition of colloidal particles in saturated porous media are of great importance in many fields of science and engineering. A thorough understanding of particle filtration processes is essential for predicting the transport and fate of colloidal particles in the subsurface environment. Particles migrating through a porous medium can remain in suspension and be transported due to advection and dispersion phenomena, or be retained due to filtration and deposition onto the porous matrix. In particular, in the framework of the FP7 project Nanorem (G.A. Nr. 309517), the application of nanoparticles for groundwater remediation is the key research question. Colloid transport is a peculiar multi-scale problem, and pore-scale processes have an important impact on the transport at the larger scale. In this study, colloid transport modelling was carried out at different scales, from the pore scale (applying pore-network models) up to the full field scale. Assessing the mechanisms that control the mobility of reactive nanoparticles is of pivotal importance in the design, implementation, and performance evaluation of field applications. While numerical models for the simulation of dissolved contaminants transport are widely available, field scale models of nanoparticles with proven predictive ability are yet to be developed. This is mainly because the fundamental controlling mechanisms for the transport of nanoparticles in the subsurface at the field scale are not well understood.
Using pore network modelling we simulate fluid flow and transport of colloids within a network of interconnected pores (Raoof et al., 2013). Colloidal processes such as deposition and aggregation are implemented at the scale of individual pores. Averaging over the network domain composed of several pores, we derive macro-scale parameters to be used within field scale models (Raoof et al., 2010).
Transport of concentrated nanoparticle suspensions in porous media is affected by the rheological properties of the dispersing fluid (shear thinning) and by particle deposition and filtration in the porous matrix, which result in porous medium clogging (i.e. reduction of porosity and permeability). Moreover, the kinetics of particle retention is strongly influenced by the ionic strength of the pore water. Up to date, modelling of colloid transport in the presence of such complex interaction phenomena has been mainly faced in one-dimensional Cartesian coordinates for the simulation of laboratory column tests (Tosco et al., 2009; Tosco and Sethi, 2010), or at larger scales in simplified radial domains (Tosco et al., 2014), as implemented in MNMs (www.polito.it/groundwater/software/MNMs.php). In this work, a modelling tool for the simulation of colloid injection and transport under transients in ionic strength in more complex scenarios is developed and validated. To this aim colloid transport equations were implemented in the well-known transport model RT3D (Clement et al., 1998). The tool can be used for multi-dimensional simulations, and the approach is validated through comparison of results from MNMs and RT3D for a one-dimensional domain.
References
Clement, T.P., Sun, Y., Hooker, B.S., Petersen, J.N., 1998. Ground Water Monitoring and Remediation 18, 79-92.
Raoof, A., Hassanizadeh, S. M., & Leijnse, A. (2010). Upscaling transport of adsorbing solutes in porous media: Pore-network modeling. VZJ 9(3), 624-636.
Raoof, A., Nick, H. M., Hassanizadeh, S. M., & Spiers, C. J. (2013). PoreFlow: A complex pore-network model for simulation of reactive transport in variably saturated porous media. Computers & Geosciences, 61, 160-174.
Tosco, T.; Sethi, R. Environmental Science and Technology 2010, 44(23), 9062-9068.
Tosco, T.; Tiraferri, A.; Sethi, R. Environmental Science & Technology 2009, 43(12), 4425-4431.
Tosco, T.; Gastone, F.; Sethi, R. Journal of Contaminant Hydrology 2014, 166(0), 34-51.
Background/Objectives. Dissolved-phase 1,1,1-trichloroethane (TCA) is particularly
susceptible to hydrolysis and dehydrohalogenation reactions at elevated temperatures. For
example, laboratory-derived degradation rate constants for TCA increased from 0.068 day-1 at 50 Celsius (ºC) to more than 0.3 day-1 as temperatures approached 70ºC. A hot-water
injection/recirculation remediation system was designed, constructed and operated for 18 months to establish in situ treatment of TCA in groundwater. This work follows a previous work where bench-scale testing, thermal modeling, and field-scale pilot studies to evaluate the feasibility of using injection/recirculation of hot water to remediate dissolved and separate-phase TCA in groundwater at the Site. Remedial objectives included elimination of separate-phase TCA in the source area and decrease of dissolved phase TCA concentrations to below the groundwater standard of 200 micrograms per liter (ug/L).
Approach/Activities. The results from a field pilot study performed in 2007 and 2008 were used to develop a three-dimensional, numerical groundwater flow and thermal transport model for the surficial aquifer. A capture zone analysis was also performed to design an injection/recovery well network to propagate heated water throughout the desired treatment zone, as well as contain the source area and prevent downgradient migration of the dissolved constituents. In 2008, a fullscale remedial system was designed, which consisted of an automated hot water injection/recirculation system that used three downgradient recovery wells, a 108 kilowatt tankless water heater to heat the recovered groundwater to approximately 80ºC, and two injection wells near the suspected source area. This system was operated for an 18-month period (October 2008 to March 2010).
Results/Lessons Learned. TCA concentrations in the main source area were reduced from an
initial value of 8,200 ug/Lin August 2008 to <1.0 ug/L in March 2010, at which point the
remedial system operations were terminated. 1,1-Dichloroethene (DCE), generated via abiotic hydrolysis and dehydrohalogenation of TCA, increased from approximately 12 ug/L to 82 ug/L during the November 2008 to April 2010 monitoring period. 1,1-Dichloroethane (DCA) also was produced, likely from biotic reductive dechlorination of TCA, increasing from 25 ug/L to 150 ug/L. Follow-on hydraulic and thermal transport numerical modeling were performed to improve the model’s predictive ability by comparing simulated results to actual field results.
Model setup, calibration, and results from these evaluations also will be discussed in the paper. Future activities include long-term monitoring to document the declining DCE and DCA trends
Human industrial activities have resulted in a great number of contaminated land areas in Europe and the rest of the world. Management of those areas has to prevent any unexpected risk to humans or the environment. In order to ensure sustainable re-development of contaminated areas, there is need for innovative solutions to prevent and mitigate unacceptable risks to human health or the environment; particularly where problems seem intractable or the impacts of current treatments seem severe.
The use of nanoparticles in remediation has been advocated as offering a step-change in remediation technology performance and in extending the range of treatable problems. Yet this transition has not gained full momentum so far as was anticipated some years ago. Can nanoremediation really be the answer? What are the most important factors governing the overall market opportunity for, and sustainability of, nanoremediation projects?
Laboratory scale work implies nanotechnologies could offer a step-change in remediation capabilities: treating persistent contaminants, avoiding process intermediates and increasing the speed at which degradation or stabilisation can take place. In 2007 the European Commission Joint Research Centre forecast that the 2010 world market for environmental nanotechnologies would rapidly expand to be around $6 billion, with nanoremediation accounting for a substantial proportion of this. However, in practice, adoption of nanoremediation has been slow. While some projects may have gone unreported in the technical literature, the FP7 NanoRem project identified only around 70 examples of field scale applications of nZVI worldwide as of early 2014 (Nano-scale zero-valent iron – nZVI – is the most commonly used nanoremediation material). Only 17 of these were in Europe (cases in the Czech Republic, Germany and Italy), although bench-scale nanoremediation research is widespread across the EU. The majority of 70+ applications in the field noted by NanoRem were in situ injections of modified nZVI. From a commercial and practical standpoint therefore, nanoremediation has been largely as a niche technology for treating chlorinated solvents, competing with a range of alternatives.
The NanoRem project has set itself the goal of achieving a step change in the development and use of nanoremediation technology in Europe. To reach this goal does not only depend on the creation of new research information, but also on the transmission to remediation practitioners and encouraging their use of that information. As part of this process it has been engaging with a large number of stakeholders to investigate the principal drivers perceived as having an important effect on both the sustainability of the technology and its market opportunities.
This work has included discussion with the European stakeholder networks, NICOLE and COMMON FORUM, face to face discussions with remediation practitioners at workshops (including a dedicated workshop in Oslo in December 2014); via focus groups and questionnaires.
Regarding the sustainability, a wide range of stakeholders have been brought together to discuss their hopes and fears related to nanoremediation technology at two events. These debated environmental, economic and social concerns, which would likely influence the sustainability of a nanoremediation project. The most important factors, which would block or facilitate nanoremediation, were identified from the point of view of these cross-sectorial practitioners. Regarding the possible opportunities for nanoremediation market placement and penetration, push and pull factors have been systematically collected to inform sound scenarios for the market development in the EU by 2025.
This presentation will review the main findings of this process at the midpoint of the NanoRem project, “hot of the press” of the NanoRem deliverable on “Exploitation Strategy and Consultation” due April 2015.
Overview. Multiple areas of 1,1,1-trichloroethane (TCA) contamination were encountered
during investigations at a former manufacturing plant. In one area, leaks from a former degreaser pit resulted in TCA concentrations exceeding 1% of its aqueous solubility (13.3 milligrams per liter). Dense non-aqueous phase liquid (DNAPL) was also present in the source zone. The objective of the remedial effort was to reduce contaminant concentrations in the source zone to below the 1% TCA solubility value. After extensive laboratory treatability testing, the selected remedy for the site included heating of the saturated zone in the source area to enhance TCA removal via hydrolysis, followed by the injection of sodium persulfate to oxidize any remaining TCA and hydrolysis byproducts. Remedial investigations were conducted to develop the remedial design basis for the project and help achieve the site remedial objectives, understand hydrolysis reaction rates and byproduct formation, identify oxidation rates at varying temperatures, and estimate the remedial time frame.
Approach/Activities. Bench-scale laboratory analyses and thermal modeling were conducted
prior to implementation of the remedy. Bench-scale analyses evaluated the oxidation of TCA
using alkaline-activated sodium persulfate. A second phase of laboratory testing included
comparison of multiple activation methods, including heat (45oC), chelated iron (using citric
acid, ferrous sulfate, and ferric citrate), and hydrogen peroxide. In situ heating was accomplished by recirculating recovered groundwater through a tank-less hot water heater prior to reinjection into the source area, resulted in a maximum temperature rise of 70oC. At this temperature, TCA should autodecompose at a half life <1 day according to the Arrhenius equation. 1,1- Dichloroethene (DCE) and acetic acid are TCA hydrolysis byproducts; which are relatively easy targets for oxidation using sodium persulfate. The remedial approach included groundwater recirculation for a 6-month period, followed by a single injection of sodium persulfate as a polishing step.
Results/Lessons Learned. Treatability study results documented a nearly 50% reduction in TCA concentration by heat alone (due to hydrolysis) over a 13-day test period. Heat and hydrogen peroxide activation both resulted in a 100% reduction of TCA; however, volatilization was responsible for the removal of TCA mass in the hydrogen peroxide activated sample. The results of the treatability study indicated that heat-activated persulfate was highly effective for degrading TCA, and ferrous iron activated persulfate using high oxidant strength was also moderately successful. Heat alone offered moderate success over the 13 day test and it was predicted that a sustained heat application at higher temperature would enhance effectiveness as well as promote dissolution of DNAPL. The prolonged enhanced hydrolysis produced by heating the formation followed by persulfate injection utilizing the residual heat as an activator was completed in May 2011. Initial results 2 months after the injection of persulfate resulted in >97% reduction of TCA in the source area and destruction of >90% of the DCE byproduct.
Background/Objectives. Approximately 8 million litres of petroleum light non-aqueous phase liquid (LNAPL) reside in the subsurface at the former automotive facility.
Several petroleum types, ranging from gasoline to hydraulic oil, are present in 15 distinct
LNAPL plumes. Bench-scale treatability testing was used to compare the technical and fiscal
viability of five remediation technologies to address recoverable and residual LNAPL present at the site. The bench-tested remediation technologies included hydraulic recovery, surfactantenhanced recovery (SER), thermal-enhanced recovery, in-situ chemical oxidation (ISCO), and surfactant-enhanced in-situ chemical oxidation.
Approach/Activities. Undisturbed soil samples were used to support hydraulic recovery, SER,
and thermal-enhanced recovery. Water drive testing was performed on undisturbed soil cores to evaluate the fraction of LNAPL that could be recovered using hydraulic pumping. Sequential tests were performed following water drive testing to measure the incremental increase in LNAPL recovery using a surfactant solution and hot-water flood. The surfactant and solution strength was determined based on interfacial tension testing of site LNAPL and groundwater amended with various surfactants at a range of concentrations. Site LNAPL and groundwater were used to support ISCO and surfactant-enhanced ISCO testing. Site LNAPL was added to groundwater amended with sodium persulfate or Fenton’s reagent
(along with multiple activation methods) to determine if direct oxidation of the LNAPL was
feasible. Surfactant-enhanced ISCO was also evaluated on LNAPL-groundwater mixtures using surfactant and sodium persulfate. Broad total petroleum hydrocarbon (TPH) analysis was used to evaluate the performance of in-situ thermal destruction (ISTD), ISCO and surfactant-enhanced ISCO on preferential removal of low molecular weight constituents from the LNAPL.
Results/Lessons Learned. This broad bench-scale testing program was unique and provides
insight into commonly-held beliefs of the capabilities and cost effectiveness of common
remediation technologies to address LNAPL contamination. The testing results provided a direct comparison of the capacity of remedial technologies to recover/destroy LNAPL, as well as a basis for a cost benefit analysis of each remedial approach.
Background. The property is a former lumber mill that was developed in 1912 as a manufacturing plant for woodworking machines, and was sold and converted in 1919 to manufacture truck and automobile axles. Lubricants, cutting oils, and metal stock are currently utilized at the 600,000-square foot facility.
Subsurface investigations identified surficial anthropogenic fill material, underlain by a 3-inch to 6-foot thick layer of sawdust and wood fragments, underlain by native silt and clayey silt. The largest mass of wood matter was a 4- to 6-foot thick deposit beneath a parking lot near a river bordering the property.
The thickness of the wood matter decreased between the parking lot and the river, with the native soil transitioning to riverine sand deposits. Environmental investigations identified 18 Recognized
Environmental Conditions (RECs). In addition to RECs consistent with axle manufacturing operations, one unusual REC was identified; a dissolved barium (Ba+2) groundwater plume was found beneath the parking lot. Dissolved barium concentrations ranged up to 25 milligrams per liter (mg/L), well above the 2.0 mg/L state cleanup standard. This was the only area where groundwater standards were exceeded.
Approach. The investigation data were reviewed to evaluate the origin and distribution of barium. Plant operations did not use products with high barium content, suggesting the barium was naturally occurring. Results from 166 soil samples collected from 99 borings did not identify a barium source area. Groundwater data indicated the Ba+2 groundwater exceedances were limited to the parking lot. Fill material samples from the parking lot did not contain elevated concentrations of barium, however the presence of the fill material within the plume indicated a connection. A conceptual site model established
a correlation between the dissolved Ba+2 plume, groundwater depth, and thickness of organic fill deposits.
Barium solubility is influenced by geochemical conditions. A groundwater geochemical study was undertaken using a network of 39 monitoring wells. Groundwater samples were analyzed for 13 geochemical parameters. Results indicated groundwater in the dissolved Ba+2 plume contained elevated levels of chloride, ferrous iron, methane, and total dissolved solids; little to no sulfate or nitrate; negative oxidation reduction potential (ORP); and low dissolved oxygen (DO). The results were indicative of strongly anaerobic conditions. The organic fill material was promoting microbial activity that depleted DO concentrations. This reducing environment promoted the disassociation of stable, insoluble Ba+2 complexes with concurrent reduction of anions (e.g., sulfate to sulfide), making Ba+2 soluble in groundwater beneath the parking lot. The geochemical investigation showed DO concentrations rebounding from 0.15 mg/L to 1.3 mg/L approximately 10 feet downgradient of the fill material and within the native riverine sand deposits. These downgradient conditions allowed barium complexes with lower solubility to precipitate; dissolved Ba+2 concentrations decreased from 19 mg/L to 0.96 mg/L.
Results. Since the parking lot was the only area where groundwater constituents exceeded regulatory standards, active remedial measures such as excavating the organic fill or treating groundwater with Ba+2 binding agents were initially considered. The geochemical study demonstrated the Ba+2 plume was a localized phenomenon created by interactions among the fill material, microbial community, and groundwater. The study also found downgradient Ba+2 concentrations decreased under naturally occurring conditions as DO concentration increased through surface water infiltration and the confluence of groundwater with the river. The final recommendation was to address the Ba+2 plume through natural attenuation. The regulatory agency agreed, and the project received a No Further Action determination.
Background/Objectives. Enhanced reductive dechlorination (ERD) applications rely on
injection of organic carbon substrates over time to establish reducing conditions, foster microbial growth, and drive biodegradation of chlorinated volatile organic compounds (VOCs). Common organic carbon substrates include soluble compounds such as ethanol, lactate, molasses, and cheese whey, while slow-release compounds include emulsified vegetable oils (EVO) and other propriety amendments. Reported half-lives for these soluble compounds range from 10 to 60 days, suggesting these amendments may last several months or longer depending on the microbial ecology and dosing strength, while slow-release compounds may last several years. Typical remedial strategies involve the use of fate and transport modeling to develop preliminary remedial goals (PRGs) with active injections proceeding until PRGs are met, followed by a transition to monitored natural attenuation (MNA) as a polishing step. MNA transition strategies are typically based on general assumptions about TOC longevity and redox recovery following the active carbon injection period. The primary objective of this study is to gather empirical data to refine these assumptions based on a broad assessment of ERD sites that have transitioned to
MNA. This information is intended to help practitioners fine-tune injection and MNA transition
strategies.
Approach/Activities. Data from multiple ERD sites that have completed active carbon
injections and are currently undergoing post-injection monitoring will be evaluated to determine
(1) the duration of elevated TOC (above background) and (2) the timeframe for groundwater to recover to ambient redox conditions. Sites will be grouped based on common climatic and hydrogeologic factors (aquifer type, depositional environment, groundwater velocity, etc). This study will discuss one large full-scale case study to demonstrate the analytical approach and then summarize the results from the remaining sites.
Results/Lessons Learned. Preliminary post-injection results indicate that low, but elevated TOC concentrations often linger longer than predicted where soluble carbon substrates were injected at sites with lower groundwater velocities. Thus, low-level TOC concentrations can extend ERD treatment for up to two years after the last carbon injection, but can also delay the timeframe for groundwater to recover to ambient redox conditions. This may have implications for sites where treatment train remedies are being considered for other contaminants (e.g. chemical oxidation of 1,4-dioxane). At sites with high groundwater velocities, TOC concentrations dropped fairly rapidly following active injection period suggesting that was carbon washing out prior to complete degradation. Overall, the preliminary results suggest the both the substrate type and hydrogeologic setting influence TOC longevity and redox recovery. Thus, remedial strategies should be fine-tuned based on site-specific performance monitoring results.
Background/Objectives. The ability to perform both short and long-term operation of injectionbased in situ remedies is dependent on the aquifer matrix, which acts as a physical regulator during the injection events. Because an aquifer has a finite capacity for (1) fluid accommodation, and (2) the dissipation/assimilation of by-products stemming from reactions (e.g. precipitation, gas generation, biofouling) associated with the injected fluid, injection flow rates and pressures will shift both during injection events and over the lifetime of an injection-based remedy. The ability to “tune” the implementation of a remedy to optimize its performance, and ultimately reduce the lifecycle costs of the remedy, relies on anticipation of the above constraints.
Approach/Activities. Three field examples will be presented to demonstrate the theory and
science behind “Aquifer Tuning”, focusing on how aquifer structure (e.g. lithology, porosity,
permeability) and groundwater geochemistry (e.g. salinity) can have profound effects on short and long-term operation of injection-based systems. These examples will demonstrate how (and to what extent) aquifer constraints reduced remedy effectiveness, increased costs, and/or contributed to the risk of remedy failure. In addition, how these constraints were overcome to optimize the performance of the remedy and ultimately reduce the overall cost of remedy implementation will be discussed.
Results/Lessons Learned. The first field example is an injection site where a physical constraint (a semi-confining layer overlying the targeted injection interval) affected injection flow rates and inhibited reagent distribution.. After the realized affects (greater than anticipated) of the physical constraint, the injection approach was tuned to more effectively distribute the injection solution in a cost effective manner.
The second field example demonstrates how carbon loading must be considered to minimize
both short and long-term aquifer permeability reductions resulting from biogenic gas formation.
An instance of excess TOC loading resulted in immediate reduction of aquifer permeability
which was tuned by monitoring the dissipation of generated biogenic gases, re-establishment of baseline injection capacity and greater control on TOC loading of subsequent injection events The last field study demonstrates the importance of injection solution composition when delivering fluid into a saline environment. to prevent clay particle dispersion, which can result in an unrecoverable reduction in injection capacity. An adapted injection solution, designed to a compatible salinity of the aquifer, resulted in recovery of injection capacity and the continuation of the injection-based remedy.
Contamination of groundwater by industrial organic and inorganic pollutants is a global widespread problem. In recent years, the use of Iron nanoparticles is gaining a special attention as a promising technology for in situ remediation of contaminated aquifers. Injection of nano iron particles into contaminated groundwater is already applied nowadays. Yet, there are still obstacles for efficient and economically viable application of this technology. In particular, due to their high surface area, nano-size and high density nano iron particles in general and nano zero valent iron (nZVI) specifically, are inclined to agglomerate and attachment to subsurface solid matrix. Potential solutions for this problem include surface modifications of the particles to increase their stability and fracturing of the porous medium increasing its permeability and subsequently the particles mobility in the contaminated subsurface. Nevertheless, the knowledge about transport potential of nano iron particles in fractured media is still in its scarcity. Based on previous studies with colloidal particles, fractures are likely to be favorable carriers for nano iron particles and could facilitate their transport and the efficient application of nano iron particles at the field.
In this study we explored and quantified the mobility of several types of nano iron particles in fractured media. Stability tests and transport experiments were carried out in both low-salinity artificial rain water and in much more saline solutions, representing realistic groundwater composition. Some of the particles tested were also stabilized using carboxymethyl cellulose (CMC). The mobility of the particles was tested by transport experiments carried out in the laboratory. These experiments were carried out in a naturally fractured chalk core excavated from the field site in the northern Negev Desert, Israel. The highest particles recovery received in these experiments was of CMC stabilized Carbo-Iron® particles. Carbo-Iron® particles are consisting of activated carbon colloids and anchored deposits of nZVI clusters. The activated carbon acts as a spacer preventing agglomeration of the deposited nZVI structures. Additionally Carbo-Iron® particles have a more negative surface charge than pure nZVI that comes from the properties of the activated carbon colloids. These particles showed higher stability in our stability tests as well.
The next step in this research is therefore injecting CMC stabilized Carbo-Iron® particles in a natural fracture network in the field and analyze the particles recovery under natural conditions in larger scale (tens of meters). Preliminary tracer tests are being done nowadays to accurately define the fracture properties using soluble tracer experiments.
Sometimes it is immediately obvious that a site is complicated because of characteristics such as size, infrastructure, subsurface heterogeneity, or mix of contaminants. In other cases, a site’s complicated nature is realized only after the fact, when remedial actions fail to achieve remedial action objectives. Matrix diffusion is a reasonably well-known phenomenon whereby contamination migrates over time into low(er)-permeability strata and evades treatment, only to back-diffuse after remedial intervention, hampering or precluding short(er)-term achievement of drinking water type groundwater resource restoration goals.
The focus of this panel will be the underlying causes of and possible responses to this prevalent problem, popularly known as “rebound.” The panelists are leading researchers and practitioners working to understand the nature of the problem and evaluating and employing remedial strategies and tools. An important component of this panel will be upfront efforts to reach out to a wider group of researchers and consultants to identify scientific and engineering insights and issues, which will be incorporated into the discussion. Discussion topics will include:
• Is back diffusion really a problem? There are a number of possible explanations for
rebound. Before concluding that back diffusion is the problem, other possible
explanations and contributing sources must be ruled out.
• If rebound is occurring at a particular site, how serious is the problem and what are the
most important attributes? Current approaches to plume delineation may not be
producing accurate conceptual models of plume geometry and volume. A side effect is
inaccuracy in the matrix volume subject to diffusion and storage. Are emerging “highresolution” tools and strategies useful?
• What is/are the most appropriate and feasible response(s)? Possible responses are not
mutually exclusive, and they range from no action through passive to active remediation
over various temporal and spatial scales. Recent field results suggest that the matrix may
not be entirely “defenseless.” Not all sites that have low-permeability zones are
experiencing rebound, suggesting that attenuation processes may be at work.
The discussion will evaluate whether there have been developments in remedial technologies and scientific understanding of requisite persistence and/or matrix penetration attributes.
Background/Objectives. A new passive and sustainable remediation concept termed horizontal treatment (HRx) wells is presented that utilizes horizontal wells filled with reactive media to passively treat contaminated groundwater in-situ. The approach involves the use of directionally drilled horizontal wells filled with granular reactive media generally installed parallel to the direction of groundwater flow. The design leverages natural “flow-focusing” behavior induced by the high in-well hydraulic conductivity of the reactive media relative to the aquifer hydraulic conductivity to passively capture and passively treat proportionally large volumes of groundwater within the well. Clean groundwater then exits the horizontal well along its downgradient sections. Many different types of reactive media could be used (zero valent iron, activated carbon, IX resins, zeolite, phosphate, chitin, etc.); therefore, this concept could be used to address a wide range of contaminants. In contrast to many other in-situ remedial technologies, this technique may be appropriate and successful for low-permeability aquifers. Furthermore, the approach requires no above-ground treatment or footprint, limited ongoing maintenance, and allows the use of a wide range of reactive media that can readily be removed/recharged.
Approach/Activities. A series of quantitative three-dimensional flow and transport simulations
were completed utilizing MODFLOW and MT3D and interpreted with three-dimensional
visualization tools (EVS) to assess the general hydraulic performance, capture zones, residence times, effects of aquifer heterogeneity, and treatment effectiveness of the concept. To confirm the basic hydraulic and treatment concept and verify the model results, a three-dimensional physical model (sand tank) was constructed with zero valent iron (ZVI) used as the reactive media to treat a suite of contaminants.
Results/Lessons Learned. The modeling results demonstrate that capture widths greater than 50 feet can be achieved, and that near-immediate reductions in down-gradient concentrations and contaminant mass flux can be achieved. Compared to other remedial alternatives, the HRx system has several green and sustainable attributes that contribute to the triple bottom line (environmental, social and economic benefits). The approach greatly reduces carbon footprint and recurring and cumulative energy demands. Because the system does not require groundwater extraction, life-cycle water consumption is negligible, and the above-ground infrastructure is minimal. From an economic perspective, the annual and life-cycle costs are substantially lower than most conventional alternative remedial strategies, particularly if remedial performance goals are focused on reducing risk through eliminating contaminant mass discharge.
Background/Objectives. Site contractual obligations required remediation of a 3 mile long
trichloroethene (TCE) plume, to maximum contaminant
levels (MCLs) within 10 years. This presentation addresses the implementation of an adaptive approach to design and operation of the remedy to achieve site closure within the required time period. Upon ARCADIS taking control of the site, the plume dimensions were defined by reinterpreting all available site data. The initial delineation of the TCE plume had been based on approximately 20% of all the wells installed, and as a result, the plume was depicted as a 3 mile long contiguous mass. Due to the limited understanding of high permeability flow paths, pumpand- treat wells were installed where access was available - in many cases away from the main body of the TCE plume – rather than at strategic locations within the plume. This resulted in artificial widening of the plume that further obscured an accurate understanding of its geometry.
Approach/Activities. The plume was divided into five individual treatment areas, each with its
own conceptual site model (CSM) based on plume size, plume age, period of performance, and site conditions. Enhanced Reductive Dechlorination (ERD) was the primary remedial strategy in two areas, while pump-and-treat followed by re-injection was the focus in the remaining three areas. ERD was largely successful in areas where reagent distribution was achieved; however, well fouling, aquifer heterogeneities, and an insufficient well network lead to the cessation of ERD. For these reasons and the fact that significant mass reduction could be achieved, full scale implementation of pump-and-treat followed by re-injection was pursued. Sitewide MCLs were achieved by installing dual purpose extraction/injection wells over time, in an organized sequence after careful review of operational data and surrounding well data. High permeability zones were identified and remedial efforts were focused on the areas that would impact the greatest mass while still maintaining plume capture. Operation of strategically placed wells, optimization of remedial systems, and an adaptive design have combined to reduce the plume size by more than 95% in the last 4 years and allowed for greater operational flexibility and subsequently, greater efficiency.
Results/Lessons Learned. Regulatory collaboration was a critical component in developing and understanding accurate CSMs and in achieving site closure. A collaborative environment grew and facilitated better communication and site management. Full site closure will be achieved after regulatory-assigned compliance wells meet MCLs for three consecutive annual samples.
The 3 year pre-closure monitoring phase is scheduled to begin in 2012 and is expected to be
complete in 2014.
Background/Objectives. Karst terranes present unique challenges to geologists and engineers tasked with remediating groundwater where chlorinated or recalcitrant compounds have been released. Groundwater movement and chemical transport in karst aquifers is often complicated by extreme heterogeneity and anisotropy, turbulent flow, and transport pathways that are impracticable to characterize precisely. However, karst aquifers are not uncommon. These aquifers are present on all continents and crop on more than 20 percent of the earth’s land surface; at least 20 percent of the world’s population is partly or entirely dependent on water derived from them. Given this knowledge, it is important to understand how karst sites are currently being remediated. The work depicted here represents results from the first part of a two-part study designed to (1) examine current
remedial actions selected for sites located in karst terranes, and (2) evaluate their appropriateness and effectiveness.
Approach/Activities. Drawing on review of 73 remedial action plans from sites where groundwater remediation in karst terrane is mandated, as well as the authors’ experience
at over 15 karst sites throughout the United States, the following aspects of karst aquifer remediation were examined: addressing source zones, implementing engineering controls to eliminate exposure pathways, the use of institutional controls and groundwater management strategies, and performance monitoring strategies.
Results/Lessons Learned. Remedial approaches applied at karst sites are usually the same as those applied at non-karst sites. For example, source zones have most commonly been addressed by excavating unconsolidated material, and the most-common groundwater management strategy selected in the remedial action plans evaluated is monitored natural attenuation. However, karst-specific characteristics are often not considered when applying these technologies. In the case of source removal, the benefits of removal via excavation need to be evaluated against the potential for mobilizing contaminated soils into the karst aquifer, where they can act as long-term secondary sources of contamination to groundwater. The monitoring component of monitored natural attenuation is frequently accomplished using water-quality data obtained from wells that have not been demonstrated by tracer testing to be monitoring groundwater that is in transit and connected to the source zone. Springs that discharge the groundwater-of-interest are arguably the best places to monitor for attenuation, yet such monitoring is rarely required to be performed.
A number of remedial approaches that may be specific to karst are underused. For example, the interconnected, variably saturated epikarst present at many karst sites has been shown to be an excellent means of collecting and containing volatile vapors, but is rarely exploited in this fashion.
Performance monitoring of groundwater remedies in karst terranes requires special techniques. For remedies that involve moving groundwater (e.g., containment) tracer tests must be included to assess performance. The best places to monitor remedial performance are springs, surface streams, and groundwater-abstraction points. Reliance on monitoring well networks to assess performance has often been shown to be inappropriate. Despite this, the most-common form of groundwater monitoring required in karst-site RODs is the traditional, monitoring-well-based approach.