Contaminated sites are often characterized by the presence of a multitude of chemicals. Although it is possible that each chemical on its own does not give rise to human health risks, the question arises whether the assessment of combined (or cumulative) exposure to certain chemicals would not change the outcome of the risk assessment. Review of approaches in cumulative risk assessment reveals a wide range of methodologies, varying from consideration of the organ where the effect occurs till detailed evaluation of mode of action. Cumulative risk assessment should consider both aspects of exposure and risk characterization. In contaminated sites assessment in Flanders, the exposure assessment typically is of a cumulative type, so the focus of the developed methodology is on the risk characterization part. The assumption of additivity (no interaction) was chosen as this is the most appropriate option in case of low dose exposures. For each regulated chemical, critical and subcritical endpoints of effects were listed by exposure route. Distinction was made between local and systemic effects. Endpoints were grouped into effect classes, which were the basis to combine individual risks. For non-threshold carcinogens, no distinction is made with regard to affected organ. The key table with effect classes and allocation of each chemical to its relevant classes per route of exposure forms the basis of the further methodology, that describes approaches to look at cumulative risk assessment in a) site screening based on remediation values, b) site risk assessment, and c) urgency for remediation. As introduction of cumulative risk assessment in contaminated sites assessment could have a vast impact on dossier outcomes, an approach for use in current practice focusing on remediation urgency was developed. In parallel, a preferred approach was developed as well for use throughout all steps of the site assessment (screening, risk assessment, urgency). The latter approach, which extends on the first approach, can be adopted gradually as part of a review of chemical information and remediation values.
The approach will be demonstrated for a number of cases.
Background
It is well established that total concentrations of soil contaminants are useful to indicate pollution; however they do not necessarily indicate risk. Alternative measures can be used to denote the bioavailable fraction, the so-called bioavailability of soil contaminants. If bioavailability is accounted for in risk assessment models, the accuracy will be improved and this would lead to more reliable decisions on the need to remediate and on how much soil needs to be remediated. Risk-based management approaches based on bioavailability principles have a potential to be more cost effective than conventional approaches based on total concentrations. Furthermore, it will open up for alternative site specific management methods based on immobilization of contaminants (reducing bioavailability). To date, many soil testing methods have been developed to predict uptake, toxicity and degradation potential of soil contaminants, but no generally accepted methodology to incorporate contaminant bioavailability in risk assessment models exist. Within the SNOWMAN funded project IBRACS we have evaluated the option to use a passive sampler method, in combination with the equilibrium partitioning theory, as a basis for a risk assessment framework. The proposed framework, with examples, will be presented at the conference.
Methods
An equilibrium passive sampler polyoxymethylene (POM) was used to assess the bioavailability of native polycyclic aromatic hydrocarbons (PAHs) in 22 diverse historically contaminated soils (coke work, gas work and wood tar sites), alongside the lipid concentrations in exposed worms (Enchytraeus crypticus). For details about methods and results, see Arp, et al. (2014).
Results and discussion
The soils studied covered a wide range in soils properties, including texture, pH and organic carbon content. The amount of total organic carbon in the soils (TOC) varied from 2 – 49%. Some samples were low in black carbon (4% of TOC), whereas others, particularly those from coking sites, were rich in black carbon (26 – 95% of TOC). Total concentrations of PAHs in soils varied considerably (0.27 - 2651 µg/g); so did the corresponding POM derived pore water concentrations (0.02 - 460 µg/). One major finding was that the TOC normalized partition coefficients for PAHs was about one order of magnitude higher than those recommended by national agencies, like the United States Environmental Protection Agency (USEPA) for sediments and the Netherlands' National Institute for Public Health and the Environment (RIVM) for soils and sediments, i.e. the sorption of PAHs was significantly stronger in the historically contaminated soils than in “spiked soils” normally used in toxicity experiments. This illustrates the need to actually measure pore water concentrations in historically contaminated soils as a first step in a site specific risk assessment that accounts for bioavailability.
Soil quality standards and critical limit values for non-polar organic compounds, like PAHs, are in most countries based on the assumption of equilibrium partitioning. According to this theory, freely dissolved PAHs in the pore water are in equilibrium with both the soil organic matter component and the lipid phase of soil organisms. Our results support that the assumption of equilibrium partitioning also holds for diverse historically contaminated soils; we found strong correlations between pore water concentrations and lipid concentrations for the investigated PAHs.
A key issue in a risk assessment framework that uses chemical methods for assessing a “bioavailable” concentration or fraction is to develop a reference system to which this concentration or fraction can be related. In this respect we draw on a recent RIVM compilation (Verbruggen, 2012). Here, “critical lipid concentrations” for a wide range of organisms (soils, sediments and waters) were presented. The critical lipid concept is based on the assumption that toxicity of individual PAHs is similar after entering the cell membrane. The RIVM compilation resulted in two proposed “critical lipid concentration”, corresponding to two sets of critical pore water concentrations for individual PAHs, indicating “no risk” (Maximum Permissible Concentration, SRC) or “serious risk” (Serious Risk Concentration, SRC).
We propose the following scheme to include equilibrium-based chemical bioavailability tests in site specific ecological risk assessments of PAHs contaminated soils: 1) Determine pore water concentration of freely dissolved PAHs, 2) Relate individual concentrations to risk limits (e.g. RIVM’s MPC or SRC values), using the toxic unit approach, 3) Assume additive effect and calculate the toxic unit value (if > 1, risk). This procedure is in line with the one proposed by Brand et al. (2013). The procedure was applied on two Swedish PAH contaminated sites and the outcome was compared with an assessment based on the Swedish generic guideline values. The comparison showed that the number of samples indicating risk to soil organisms decreased from 80% to 20% at one site, and from 90% to 55% at the other, when applying the proposed procedure. Accordingly, the time and money invested in extra POM analyses, which are similar to or cheaper than soil analysis, are likely to be paid off during the remediation phase.
References
Arp, H. P. H., S. Lundstedt, S. Josefsson, G. Cornelissen, A. Enell, A.-S. Allard and D. B. Kleja (2014). Environmental Science & Technology, 48, 11187−11195.
Brand, E., Lijzen, J., Peijnenburg, W., Swartjes, F. 2013. J. Hazard. Mater. 261, 833−839.
Verbruggen, E. M. J. (2012). RIVM report 607711007.
In the Netherlands, in case of expected ecological risks caused by soil pollution, the Triad approach can be used to assess site specific ecological risks. This approach combines and integrates three lines of evidence from a site to give a complete and realistic overview of the site specific ecological risks. The three fields of expertise that are combined are environmental chemistry, toxicology (bioassays) and ecological field observations. Although this method is fully validated and has been used in the Netherlands ever since it’s development (Chapman et al. 1987, Nobis 98-1-28, Jensen and Mesman 2006) a standard and legal protocol for this type of research was missing.
From an evaluation of all Triad projects in the Netherlands (project management by Bioclear) it was concluded that authorities find it hard to judge on specialized work which is not formalised in legal protocols (Wagelmans et al., 2009) which hampers decision making. In 2009 the Dutch Council of State (Raad van State) has rejected the results of a specific Triad research. Because no protocol or guidelines for sampling and sampling strategy for Triad research were present, the research protocol followed was compared to the protocol for standard chemical soil research. However, the goals of Triad research significantly differ from the goals of a standard soil research. Therefore, the protocol for standard soil research is not applicable to Triad research and alignment of protocols for standard chemical soil research and Triad research was needed.
In order to prevent future rejections of Triad research a technical guideline for sampling and sampling strategy was developed by Bioclear commissioned by SIKB (SIKB BRL protocol 2301). This protocol describes how many samples need to be taken in a given situation, how samples for different parts of the Triad need to be taken, and how to choose the reference sample. It also describes which choices need to be made and how these choices need to be documented in the sampling strategy.
At the same time a Dutch National Standard (NEN) was developed by RIVM, Alterra and NEN - in collaboration with Grontmij, Tauw, Dienst Vastgoed Defensie, Province Zuid Holland and Bioclear - named “Soil- Process of site specific ecological risk assessment of soil pollution”. This standard describes the process of ecological risk assessment (from the beginning of the project until the final decision). Based on soil use, the ecological constraints are determined by the project group (consisting of stakeholders, authorities and scientists) as well as critical ecological aspects of the polluted site. Subsequently scientists compose a research plan (based on above mentioned protocol SIKB BRL 2301). Together with stakeholders and authorities test criteria per test are determined. Agreements are made about the use of site specific references, weighing of results, method of risk assessment, site specific risk boundaries and handling uncertainties. After that, the site specific risk assessment is carried out by the scientists. The standard is meant to bring scientists, stakeholders and decision makers together. Because decision makers are involved in the project from the beginning, it is easier to make well funded decisions based on site specific ecological risk assessment studies. At this moment ISO is using both the standard and the technical guideline to make an international standard for Triad research.
During development of both the technical protocol and the Dutch National Standard we’ve tested the draft versions on practical applicability on the topsoil of a former landfill polluted with heavy metals. The site is being used for agriculture, grazing of sheep and cows. Workshops have been organized with all stakeholders (farmer, owner of the site, water regulatory authority, two different local authorities, the provincial authority and scientists). After this workshop the ecological risk assessment has been carried out.
The Dutch National Standard on ecological risk assessment and the technical guideline on sampling and sampling strategy are valuable tools in risk communication. It increases acceptance for the research plan, the results and the final decision because stakeholders have influence on the process. In the process their questions and objections will be answered and solved in an early stage. Because of this acceptance by stakeholders, it is easier for decision makers to make a final decision based on site specific research, especially now it has been formalized in standard protocols. By using the standard and technical guideline risk assessment is not a project for only scientists anymore but it becomes a process for both decision makers and scientists together. Also legal authorities can determine whether the research was performed correctly following the technical guidelines which is positive for future acceptance of Triad projects.
Risk assessment of Urban Gardening in Copenhagen
Marlies Warming a,b, Mette G. Hansen a, Peter E. Holm a, Jakob Magid a, Thomas H. Hansen a, Stefan Trapp b,*
a Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
b Department of Environmental Engineering, Technical University of Denmark, Miljoevej 113, 2800 Kongens Lyngby, Denmark.
* sttr@env.dtu.dk
Urban gardening is hip, and people in the metropoles all over the world start to grow their own food. At the same time, most if not all urban soils are polluted with heavy metals and other contaminants. In continued projects, we have for several years measured produce from the City of Copenhagen, such as potatoes, carrots, kale, radish and apples. The concentrations of arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb) and zinc (Zn) were measured by ICP-OES or ICP-MS. Concentrations of the platinum group elements platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh) and ruthenium (Ru) were also measured, but with lower frequency.
Concentrations in soil were partly below the soil quality standards set by the Danish EPA. The most polluted soils were, however, clearly above, with Pb up to 600, As 22, Cd 2.6 and Zn 1200 mg/kg dw. Concentrations of the platinum group elements in soil were low (Pt, Ir, Rh, Ru < 0.05 mg/kg) except Pd (max 1.4 mg/kg).
The European Union released legal standards for Cd (0.05 to 0.2 mg/kg dw) and Pb (0.3 mg/kg dw) in vegetables. We found very few concentrations above (Cd in spinach, 1 case). For all other heavy metals, we conducted a risk assessment based on established acceptable daily intake ADI. It was assumed that urban gardeners supply 10% of their vegetables and fruit consumption from urban gardens, and that overall consumption was the same as the Danish average. Summarized, we found no reason of concern. For no heavy metal, the intake with urban vegetables and fruits was above ADI or even close. Intake of Pb and As would increase, compared to Danish average, while intake of Cd and Ni was less than with commercial products. We did not find legal standards or ADI for the platinum group elements. Concentrations in lettuce were higher than in spinach or radish and reached 0.11, 3.81 and 1.37 mg/kg dw for Pt, Pd and Ir, but were ≤ 0.01 mg/kg for Rh and Ru.
The consideration of direct soil ingestion by adults (50 mg/d) and children (4-13 years, 200 mg/d) gives an intake of Pb above ADI at the medium and highest polluted soils. In addition, the contribution of As via soil ingestion is of relevance (40% of ADI). This risk assessment assumes daily ingestion and lifelong exposure, which is probably not the case for urban gardening.
In conclusion, we did recommend the people of Copenhagen to continue with their urban garden activities, but to take measures to reduce the attachment and ingestion of soil.
Pyrite Cinder Waste Deposition Scherpekamp
Introduction: Worldwide millions of tons of industrial solid waste such as blast furnace slag, steel slag, non-ferrous metallic slag, coal ash, coal cinder, mining waste rock, mill tailings, etc. is generated from industrial production activities every year. In the past huge amounts of these wastes were used as backfill in open mine pits often containing hazardous heavy metals with potential environmental risks. In developing countries this probably is still the case.
Problem: Back in the 1970s pyrite cinder waste from the Duisburger Kupferhütte (Germany) were deposited in clay pits at the premises of a brick factory on the riverbank of the Rhine in the Netherlands. This iron oxide pyrite cinder waste contained varying concentrations of heavy metals and metalloids and notable contained lead, zinc, arsenic and copper. Previous soils surveys carried out over the years led to the conclusion that there was a high risk of contaminants spreading in groundwater. These studies were carried out using standard soil survey techniques such as auger drilling.
ARCADIS has studied several remedial options: in situ immobilization, excavation and isolation. In order to select the right solution, evaluation of these techniques was based on a detailed geochemical study. Questions to be answered were:
• What is the real risk of leaching?
• What natural processes take place in the soil?
• How will the geochemical system respond to the remediation technique chosen?
The study was conducted recruiting qualified personnel for every stage of the work. Drilling and sampling was performed under supervision of qualified geochemists. Chemical analyses were carried out using a portable XRF (X-ray fluorescence) to gather a high resolution dataset. XRD (X-ray diffraction) to determine primary and secondary cinder and soil mineralogy in order to estimate the vulnerability of contaminants for leaching. SEM (scanning electron microscope) for measuring the distribution of heavy metals and arsenic in the detected mineralogy. All analytical work was performed or checked by qualified geochemists. Based on the various datasets a geochemical reconstruction of events was made.
Conclusion: The cinder studied was high in lead, zinc, arsenic and copper containing levels usually considered economically suitable for extraction. Most important minerals still present in the slag were: iron oxides (magnetite/maghemite/hematite), anglesite (lead sulphate), scorodite (iron arsenate) and beudantite (lead-iron-sulfate-arsenate). All these minerals are insoluble at given conditions. Scorodite might decompose under reducing circumstances.
In the first years after deposition an acidic liquor of acidic Zinc sulphate started to leach out and reacted with calcite and clay in the subsoil forming voluminous zinc carbonates, zinc silicates and gypsum. As a result an impermeable mineral layer was formed preventing any further contact between groundwater and pyrite cinder.
All together the geochemical situation is judged to be stable and no further action is considered to be necessary. Most heavy metals in the cinder are locked away in hardly soluble or insoluble minerals and the self-sealing layer at the cinder/soil boundary prevents further migration. The observed contamination of groundwater was predominantly caused by drilling undertaken during the initial site assessment phases.
Presentation: We will present the results of the geochemical study and the consequences of it for the conceptual site model as well as the remedial options considered.
Innovative Nature of the Topic.
PFOS and PFOA are emerging as contaminats of concern in many countries and authorities around the world are in the initial stages of establishing regulatory limits for groundwater. PFOS and PFOA are both difficult to remediate in soil and groundwater systems due to their recalcitrant nature and 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 and mineralizing PFOS in groundwater with minimal daughter product formation. This presentation will provide the latest in data demonstrating the reduction of PFOS by activated persulfate, utilizing a variety of activation methods, such as high pH, hydrogen peroxide and chelated iron as well as an overview of peer-reviewed papers investigating the destruction of PFOA by persulfate.
Objectives.
A twenty-one day laboratory treatability study was performed to investigate the ability of persulfate, activated by a variety of methods, to destroy PFOS in an aqueous system. Activation methods investigated include chelated iron, high pH, hydrogen peroxide and heat. Aliquots from the study were then sampled for residual persulfate, PFOS and PFOS daughter products. In addition, a survey of the current literature discussing the destruction of PFOA and PFOS by persulfate methods was performed.
Conclusions.
Initial results indicate that activated persulfate is capable of destroying PFOS under the conditions of the test. Based on the concept of the Persulfate Efficiency Number (PEN), which is the ratio of the amount of contaminant destroyed divided by the amount of persulfate used, high PEN values were obtained for iron-EDTA, hydrogen peroxide and high pH activation strategies. Very little to no daughter product formation was observed after twenty one days. The literature would indicate that PFOA is destroyed by activated persulfate as well, using a variety of different activation methods.
Complex organic contaminant mixtures (e.g., gasoline, jet fuel, chlorinated solvents, solvent stabilizers) are routinely co-disposed at hazardous waste sites and commonly found at many if not most sites (e.g., Rao et al., 1997; McCray and Dugan, 2002; McCray et al., 2011).
In situ chemical oxidation using unactivated persulfate and permanganate have separately been demonstrated to remediate a wide variety of contaminants. Recent research has demonstrated that novel and innovative synergistic reactivity occurs when combinations of oxidants are used in tandem to treat mixtures of organic contaminants. This paper will describe results and lessons learned from a number of laboratory and field efforts where sustained-release permanganate and persulfate cylinders (MultiOx SR) were utilized as a remedial alternative that is easy to implement, has low footprint, does not require the injection of liquids, and minimizes disruption of active facilities.
A series of bench-scale oxidation experiments were performed to 1) understand the release rates of blends of permanganate and persulfate from sustained-release cylinders, 2) determine the persistence of permanganate and persulfate in site soil and groundwater, and 3) determine the kinetic rate of contaminant degradation by mixtures of permanganate and persulfate. The experimental approach included experiments in both 1) deionized water and 2) aquifer materials to evaluate the potential of natural activation mechanisms and reactive synergies resulting from mixtures of permanganate and unactivated persulfate. Both contaminant and oxidant concentrations were measured over the 30-day long experiment. Second-order kinetic coefficients were calculated and a minimum contact time was determined to ensure complete contaminant degradation of contaminant mixtures. Finally, the release of the blended oxidants from slow release cylinders was evaluated from 3-inch sections in a series of 1-D column experiments. Kinetic models were used to describe the contaminant oxidation rates and regression models were developed to quantify the release of permanganate and persulfate from MultiOx cylinders.
To validate the approach of using MultiOx SR cylinders, a conceptual framework was developed that incorporated 1) oxidant release from the cylinders, 2) soil oxidant demand rates, and 3) contaminant oxidation kinetics. Results from these experiments demonstrate that the oxidant released from the cylinders is sufficient to overcome the soil oxidant demand and can effectively degrade mixtures of contaminants in situ. The results of the laboratory experiments were then used to design a remedial plan for a field site where a co-mingled plume containing petroleum hydrocarbons and chlorinated solvents as well as the solvent stabilizer 1,4 dioxane were present.
The utilization of MultiOx cylinders can provide a simple, long-term and cost-effective approach for remediating co-mingled plumes. The cylinders can be easily emplaced in the subsurface using direct-push technology or suspended in wells for easy recharge. The sustained-release MultiOx SR cylinder has a very favorable health and safety profile, no hazardous liquid activators or injection equipment is required. Finally, there is great potential to combine the sustained-release permanganate and persulfate cylinders with other technologies such as biological remediation or other mass removal strategies (e.g. excavation, SVE) for accelerated and more efficient site remediation.
INTRODUCTION
Perfluorooctanoic acid (PFOA), as a compound of the group of PFCAs (perfluorocarboxilic acids), and perfluorooctane sulfonate (PFOS), have been widely used in industry, such as surfactants, surface treatment agents, polymers, metal coating, fire retardants, etc. during the last decades. Due to their hydrophobic and oleophobic nature, and chemical and thermal resistance, PFOA and PFOS tend to bioaccumulate and resist degradation (meeting the “persistent” and “very persistent” EU criteria) [1].
Although PFOA and PFOS have been prohibited from industrial uses, they still remain in the environment, resulting in serious health and ecological risks due to their proven toxicity and likely carcinogenic effects, furthermore, there have been several cases reporting the presence of PFOA and PFOS in some tissues and organs of both humans and animals. Therefore, the need to remove this kind of contaminants from the environment has been considered as a matter of increasing interest in the last years [1], [2].
Because of the strong fluorine-carbon bond and low vapor pressure, conventional treatment technologies such as bioremediation and direct oxidation have not offered satisfactory removal efficiencies. Whilst, on the other hand, activated carbon filters and reverse osmosis have shown effectiveness for the abatement of PFCs in water until acceptable levels, although for complete destruction of PFOS and PFOA it is necessary to incinerate the concentrated waste. Therefore, the current solutions for the removal of these pollutants are questioned in regards to their cost-effectiveness. [1]
Due to this fact, alternative technologies have been studied, such as photochemical oxidation, thermally-induced reduction, sonochemical degradation and persulfate oxidation. In case of chemical oxidation, it would be necessary to study different reaction conditions, regarding persulfate and hydrogen peroxide activation for hydroxyl radical production, in order to assess the extent of the effectiveness of all these oxidation techniques. [3], [4].
In this work it has been studied the use of activated persulfate by different ways and Fenton reagent for the removal of PFOA and PFOS, it has been also studied the defluorination grade in order to ensure a complete degradation of the pollutant.
EXPERIMENTAL
Water samples contaminated with PFOA and PFOS 0.1 mM each, were treated with Fenton Reagent and activated persulfate. Both advanced oxidation techniques were carried out by modifying the type of activator. In case of Fenton reagent, activation was carried out by adding only ferric sulfate and ferric sulfate combined with humic acids. For persulfate activation, it was used temperature (ranging from 25 to 70 ºC), zerovalent iron, alkaline conditions (pH=12) and persulfate combined with ferric sulfate and humic acids.
Reactions, carried out in glass reactors covered with aluminum foil in order to avoid sunlight, were performed at 25 ºC by orbital shaking, while for those corresponding to higher temperatures (>25 ºC), a glicerine bath with magnetic stirring was used. Concentration of contaminants, pH, fluoride in solution and remaining oxidant were followed during reactions.
PFOA was analyzed by HPLC with a Diode Array Detector (maximum absorbance 190 nm), fluoride was followed by a selective electrode in order to study the defluorination grade. Hydrogen peroxide was measured by potentiometric titration with KMnO4 and persulfate by indirect potentiometric titration of iodide (KI) with sodium thiosulfate. A glass electrode was used for pH measurement.
RESULTS
Higher removal efficiencies of PFOA were obtained with activated persulfate by temperature, zerovalent iron and ferric sulfate with humic acids. Regarding Fenton reagent, the best result was obtained when ferric salt and humic acids were used.
In terms of defluorination, persulfate activation with temperature offered the highest efficiencies for both PFOA and PFOS, while for other techniques, despite the high removal efficiencies of contaminant, incomplete defluorination rates were obtained.
REFERENCES
[1] Environmental protection agency (USA). Emerging Contaminants – Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA).
[2] Lee et al. Persulfate oxidation of perfluorooctanoic acid under the temperatures of 20–40°. Chemical Engineering Journal. Volumes 198–199, 1 August 2012, Pages 27–32.
[3] Wang et al. Electrochemically enhanced adsorption of PFOA and PFOS on multiwalled carbon nanotubes in continuous flow mode. Chinese Science Bulletin. August 2014, Volume 59, Issue 23, pp 2890-2897
[4] Yang et al. Oxidative Degradation of PFOA/PFOS with Physicochemical Techniques. PROGRESS IN CHEMISTRY. Volume 26, 7 Pages: 1265-1274.
ACKNOWLEDGEMENTS
The authors acknowledge financial support from the Comunidad Autonoma de Madrid provided throughout projects CARESOIL (S2013-MAE-2739) and from Spanish Ministry of Science and Innovation, projects CTM2010-16693 and CTM2013-43794-R.
Implementing In-situ Chemical Oxidation on an industrial EX-rated site
For the EU – LIFE+ project of VOPAK-EXPER03, VERHOEVE MILIEU & WATER co-operate closely with VOPAK, RSK and Badeco on the execution of soil remediation by applying In-situ Chemical Oxidation (ISCO).
The relevant site, VOPAK Terminal ACS, is located in Belgium. Some parts on the site are classified as historical contaminated. The existing contamination includes: chlorinated aliphatic hydrocarbons, BTEX and volatile petroleum hydrocarbons. These chemicals have polluted both soil and ground water. The remediation forms a great challenge, due to the different physical and chemical properties of these contaminants. Conventional remediation techniques can’t guarantee complete removal and the required time is inefficiently long. To cope with these factors, ISCO is implemented through the application of Perozone®. This technique injects a combination of ozone and peroxide into the soil, which can transform a variety of contaminants into harmless products.
The implementation of an ISCO based remediation on an operating petrochemical site, makes this project extraordinary. By reasons of the hazardous properties of the applied substances (ozone and peroxide), health and safety issues are priority matters on the site. Prior to the remediation an extensive safety and health plan was conducted, which includes all necessary measures during the remediation process. These measures are essential for the human health management on one hand and for the operation of the chemical storage plant on the other hand (main risks are possible corrosion of underground infrastructures, storage tanks and risk of explosion.)
The main objectives of the LIFE+ project are:
1. Demonstrate the applicability of ISCO with perozone® for the remediation of complex soil and groundwater pollution containing multiple contaminants;
2 Demonstrate the feasibility of ISCO on EX-rated sites, including adequate safety measures;
3. Demonstrate the cost and energy efficiency of the remediation technique;
4. Demonstrate the environmental benefits of the remediation technique compared to conventional remediation techniques (lower energy and water consumption and carbon emissions);
5. Disseminate the acquired knowledge.
Verhoeve Milieu & Water is mainly involved in the execution of the in-situ remediation. First, between September 2012 and January 2013 the civil engineering works and the installation of the underground remediation infrastructure were executed, including the removal of the heavily contaminated top layers in the source zone. The actual ISCO remediation began in April 2013. In total 61 ISCO filters, 32 multiple phase extraction filters and several drains were installed. Along to chemical oxidation, multi-phase extraction was initially included for tackling mass removal at the source zone. However the high concentrations has led to quick saturation of active carbon filters. After consultation with the authorities (which doesn´t permit any emission to outdoor air) multi-phase extraction was excluded from the process.
The approach of the contamination is divided in several stages, in which different site parts were treated. The first removal was conducted at the former drum storage, followed by the road section and at the end the tank farm. The activities at the former drum storage has been successfully finished at the end of 2013. At the moment the remediation at the road section is well under way and the process at the tank farm has just started. Prior of each stage an extensive risk inventory was conducted. Sometimes, additional investigations of measures were taken, when it was considered as necessary. An example of such measure is the examination of the radius of influence in the tank farm, in order to prevent damage to the corrosion sensitive tanks through high ozone concentrations.
On Aquaconsoil 2015, we like to present the results of the until then performed remediation. Which includes special attention for various risk-based assessments performed during the remediation project, to achieve a safe and effective remediation witch ISCO on an Industrial EX-rated site.
Pentachlorophenol has been used as a pesticide and disinfectant in mushroom nurseries and wood treating facilities. Soil and groundwater was contaminated with pentachlorophenol underneath a residential area at a site in Limburg, the Netherlands. The maximum concentration measured at the site was 1,700 µg/l (> 500 x Dutch intervention value), the contamination was present in a volume of approximately 6,000 m3.
Pentachlorophenol (PCP) is a compound which adsorbs strongly to soil. The contamination is difficult to remediate with most in-situ remediation techniques, due to the strong adsorption and the low volatility. However, the pentachlorophenol used is the more soluble sodium pentachlorophenate. The species that dominates in the soil depends on the pH, but at normal circumstances, the anion dominates. The anion has a much higher solubility than PCP itself, and is less inclined to adsorb to the soil. This explains why PCP contaminations can be much more widely distributed, and treatment is more viable, than anticipated based on the physical and chemical properties of PCP.
In-situ chemical oxidation, using Fenton’s reagent at a neutral pH, was selected as a viable remediation technique for the PCP contamination underneath the residential area. During the remediation access to houses and roads had to be maintained at all times.
The contaminated area was treated during two injection periods of 1-2 weeks each. Following treatment, the concentrations were monitored for one year, and the concentrations were low enough to fulfill the requirements for the site.
We would like to present the considerations for the remediation strategy, the results of the remediation and the subsequent monitoring.
The legislators (Danish Environmental Protection Agency), the Regulators (the Regional governments) and the performing part (consultants and contractors) in Danish soil and groundwater issues have a very unique working environment based on a strong scientific knowledge on all levels and very competent performers in the field. In 1983 the first Danish legislation on soil and groundwater contamination was implemented. In the last three decades, Denmark have built a unique model for dealing with soil and groundwater contamination. Studies, investigations and remediation of contaminated sites are mainly controlled by the regional authorities and to a lesser extent by private investors who want to develop an area. Civil litigation regarding remediation actions and costs between private landowners are virtually non-existing. The aim of the session is to inspire others by sharing the Danish approach of how to handle contaminated sites on all levels; our good and bad experiences on this topic, and with this, hopefully creating international working relations where we all share, learn and take home the best from each other´s practices.
We propose that the open session will consist of the following presentations and discussions:
• National Legislation of contaminated sites:
The development of the law of contaminated sites in the last 30 years.
• The regional authorities:
The aim of the regional authorities work with contaminated sites.
• KRIPP: Concept for Risk based ranking and prioritization of contaminated sites:
• Site investigation, risk assessment and remediation:
• Brownfield regeneration:
Names of presenters and titles of presentations
• Danish Environmental Protection Agency, Helle Okholm/Ole Kiilerich: Danish legislation of contaminated sites.
The Legislation behind it all and how it has developed over the last 30 years. Why has the law evolved as it has? What are the issues we are trying to solve with the law? What are the challenges we currently face? And how does the Danish legislation comply with EU legislation.
• Danish Regions, Environment and Resource, Christian Andersen: How do the Danish Regions prioritize, investigate and remediate contaminated sites.
The aim of the regional authorities work with contaminated sites.
The overall framework of the regional authority's efforts to regulate contaminated sites.
The regional authorities as a major actor for development of the approach and technology for handling contaminated sites
• COWI, Torben Højbjerg Jørgensen: Investigation and Remediation Methods, developments and state of the art.
The Danish approach to site investigations and risk assessment of contaminated sites.
Working with site conceptual models to secure a high degree of understanding the nature of the pollution and how it is dispersed into the environment.
• Orbicon, Nina Tuxen: KRIPP: Concept for Risk based ranking and prioritization of contaminated sites.
In Denmark more than 30.000 contaminated sites exist and with the yearly budgets the regions have to manage these sites, the task will last for decades. We present a risk based concept for prioritization of the effort including, mass flux calculations, impact in receptors and uncertainty analyses.
• COWI, Ninna Dahl Ravnsbæk: Brownfield Regeneration.
How the Danish approach influences development of contaminated sites as old industrial areas, harbors and old marshalling yards and prevents that regeneration activities causes contamination to spread.
Moderators: Tage Vikjær Bote & Lone Tolstrup Karlby*, COWI.
*contactperson: Parallelvej 2, 2800 Lyngby, ltka@cowi.dk
1/The French policy context
The French policy on contaminated land focuses on two main concepts. The first one is based on the risk analysis and management rather than consideration of an intrinsic level of pollution and the second on is the management based on the use of the site.
After characterization of soils to be reused, the methodology provides two types of reuse on a receiver site for road construction and as part of a development project (for which a building permit or an EIS is issued). The first criterion that has to be respected is the maintain of the soil quality of the receiving site. As there is no threshold values because the policy is based on risk based site specific approach, the soil quality has to be compared to the local geochemical background.
2/ Urban geochemical backgrounds
A soil is considered free from pollution since its characteristics are coherent with the local natural geochemical background. This is why, the approach results in comparing the state of the investigated soil with the state of the natural soils close to the zone of investigation. With this intention, the knowledge of the natural geochemical background, in particular of the local geochemical anomalies, is essential. Moreover, the characterization of pollution is important to distinguish if it implies the site or not.
However, the industrial sites are more often gathered in industrial and urban areas where an anthropic geochemical background is superimposed at the natural geochemical background. It then becomes necessary to compare data collected on the investigated site with this anthropized pedological and geochemical background.
In order to support the various actors implied in the management of (potentially) contaminated land, it was thus proposed to carry out a database of analyses of soils from urban and industrialized environment on the whole of the French national territory.
3/ The project
Bibliography about urban geochemical backgrounds in Europe shows that projects have been managed in either one specific urban area or one homogeneous region (geochemically speaking). In France, we are confronted to various natural geochemical backgrounds and also to specific industrial chronicles for each urban area. That is why we cannot deal with one urban geochemical background but with various urban geochemical backgrounds.
The project “Diagnoses of the soils in the places hosting children or teenagers” implemented by the French ministry for Sustainable development, was the occasion of launching an operation of sampling and analyses of urban soils at the level of the national territory. The collection of analyses during this operation constitutes the heart of the project “Urban Geochemical Background Database (Fond Géochimique Urbain – FGU) conducted by BRGM and funded by ADEME. Soils are analyzed for metallic trace elements, mercury, cyanides, phenol index, HC C10-C40, PAH, PCB an PCDD/PCDF. At the moment of the abstract submission, the database contains more than 44 000 analysis data collected in 200 urban areas which permits to evaluate and compare significant datas to be presented.
This presentation points out the sampling and analysis protocols of the project (selection of sampling areas, depths, sample preparations, technical analysis). The explanation focuses specifically on organic elements for which sampling, analysis and data interpretation treatment is different from metallic trace elements.
The presentation focuses then on the interpretation of the results and the comparisons between different scenarios (statistical analysis, outliers selection, restoring data) and the difficulties of the multi scale interpretations: at which scale can we have urban geochemical background values? Neighborhoods? Cities? Areas?
Objectives: To illustrate how contaminated sediments can transform and contribute into
a viable engineering structure without transportation and in an economical way.
The re-use of dredged sediments, especially contaminated sediments, is an issue of growing importance. If successful it can facilitate dredging in ports that without desilting measures would become inaccessible. The example of the works in Port La Foret in Brittany in western France, amounting to M€ 2.9 that was executed on behalf of the SAEM SODEFI Port La Forêt and proposed by the engineering company iN VIVO, shows an interesting and innovative alternative in Europe of a practice that overseas on larger projects has already proved conclusively to be effective. In all these cases, TenCate Geotube® systems are used for both dewatering flows of harbor sediments, and providing a structure of geotechnical nature. At Port La Forêt highly contaminated sediments were dredged from the marina to be injected in a flow of about 500 m3/hr into the drainage systems 5 km from the port. The dewatered silt wrapped and strengthened in these Geotube® systems was used as fill to construct a sports field parking lot. A total of 34 000m³ of liquid mud was removed from the harbor by the company MARC early 2013, to find a function in nearly 900 linear meters of drainage tubes placed on a waterproof membrane and covered with a waterproofing membrane to completely confine the sediments. A layer of fill material was then brought on to create the parking lot and the adjacent sports field. Neither ground transportation nor storage of contaminated sediments had been necessary since the sludge had been pumped to the site hydraulically from the dredge. This solution using Geotube® systems has resulted in significant savings compared to conventional landfill as well as in reduced cost compared to conventional dewatering treatments. It also represented the most positive carbon footprint.
Apart from this example in France we will give examples of works similar in approach, but different in scale, carried out elsewhere in the world.
In numerous construction projects, soil is excavated, removed from the site and used elsewhere. In doing so, there is often a danger of contaminated soil being managed in a hazardous way. The Soil Decree is an important tool for the Flemish government, not only to counter the contamination of land, but also to prevent such contamination. Ultimately, prevention remains preferable to remediation. More recently the Soil Decree aims at visualizing the potential of excavated soil as substitute to primary minerals. Through sustainable materials management it seeks to reduce the use of natural resources throughout the life-cycle of materials.
The regulation for the re-use of the excavated soil is based on the stand-still principle. There cannot be any deterioration in the current environmental condition and any increase in health or environmental risks must be avoided. Excavated soil is not to be considered as waste if it is used in accordance with the regulations of the Soil Decree and the VLAREBO. Depending on the degree of contamination with possible pollutants, the use of the excavated soil is more and more restricted. The amount of pollutants that may be present depend on threshold levels (background level, soil remediation levels that differ depending on land use type) of the Soil Decree. Non-contaminated soil can freely be re-used as "soil". Somewhat polluted soil can be re-used as "soil" if the receiving land is already more polluted or it can be re-used for building purposes in specific constructions. If the contamination surpasses certain levels, the soils must be treated in Soils Remediation Center. If the contaminated soil cannot be treated, the soil is dumped in a dump site form waste.
The protection of the environment but also the juridical protection of different actors (liability) involved is ensured by the traceability procedure. This procedure designates responsibilities and prescribes rules for excavation, transport and the use on the location of re-use. The procedure is supervised by a soil management organization that will attest the traceability of the soil by a soil management report. The soil management organization is accredited by the Public Waste Agency of Flanders (OVAM). OVAM represents the Flemish government and has the authority to check every part of the chain, and if necessary take corrective measures.
The Flemish government wants to discourage dumping of excavated polluted soils originating from remediation operations and excavation projects. It promotes recycling of polluted soils by means of environmental tax. Only soils that cannot be treated by biological, physico-chemical, or thermal means can be dumped at lower environmental tax levels. Dumping soil that can be treated is discouraged with high taxes. On yearly basis about 800,000 tonnes of soil is treated.
The data for assessing the potential of excavated soil as substitute to primary minerals is obtained in the “monitoring system for a sustainable surface mineral resources policy” in cooperation with the Land and Soil Protection, Subsoil, and Natural Resources Division (ALBON) and the Flemish Institute for Technologic Research (VITO). The monitoring system provides an overall picture of market developments on an annual basis. Although there can be substantial fluctuations about 10,000,000 m³ soil is re-used in construction projects, either as soil or for building purposes. About 1,000,000 m³ cannot not be re-used due to the poor mechanical quality. These latter soil are generally used for the rehabilitation of abandoned Quarries.
In Flanders, site rehabilitation and restoration of abandoned quarries is ensured in the Flemish Parliament Act on Surface Minerals through the granting of extraction permits and financial guarantees to ensure correct rehabilitation. These sites are not considered dump sites and only non polluted soil may be used. This is ensured by the environmental permit. In this permit a study based on a geohydrological conceptual model defines the environmental quality of the soil that can be used.
The Flemish legislation takes in account the policy on contaminated land (site specific approach) and the Waste policy based on a generic approach with guidelines values. The Flemish management policy on excavated soils already fulfills its aim at the optimal re-use of excavated soils. Nevertheless sustainable materials management could result in an even further optimization of the use of the excavated soil.
LORVER project aims at creating a production chain to obtain industrial products (biochar, fibers, metal salts etc.) and/or energy from biomass grown on soils constructed on abandoned industrial sites (www.lorver.com). This 5 year project (2012-2017), conducted by Valterra company, gathers 8 labs and 4 companies located in the Lorraine district (France). It is organized in 5 working packages: 1) listing and characterization of available derelict lands and by-products, 2) pedologic engineering (soil construction on experimental plots), 3) biomass production (poplars, hemp, nettle, hyperaccumulator plants), 4) production of compounds for industrial use and/or energy (pyrolysis) and 5) evaluation of the overall chain (economic evaluation, life cycle assessment, emergetic analysis and comparison with existing chains).
Huge surfaces (8 000 ha) of derelict land and large stocks of by-products (flying ash, water treatment plant sludge etc.) have been listed and Lorraine and are available for soil construction. However, there is a lack of regulation in France and authorization must be requested for this operation. Four experimental plots have been built: soils were constructed by mixing an industrial soil (treated by bioremediation) and metal containing sludge. Poplars, hemp, nettles and Noccea caerulescens have been grown on these plots in different conditions (with/without mycorhization and/or biochar addition). In parallel, several aspects have been investigated at the lab scale, e.g. soil and material characterization, selection of hyperaccumulator plant to reach high biomass yield and metal concentration, influence of mycorhization on plant growth, pyrolysis modeling, and influence of biochar on metal fate in soil (Rees et al., 2014). The influence of biochar on plant growth has also been investigated. The overall chain is currently assessed by life cycle assessment, and a global agroecological model of the chain is proposed. Many results have been obtained and selected examples will be presented.
Cited reference
Rees F., Simonnot M.O., Morel J.L. Short term effects of biochar on soil heavy metal mobility are controlled by intraparticle diffusion and soil pH increase. European Journal of Soil Science 65 (2014) 149-161.
The authors acknowledge the “Agence de Mobilisation Economique de la Région Lorraine” and FEDER for financial support.
The metalliferous deposits of the Cornubian Orefield in Cornwall, UK have been mined since the bronze age. The most intense period of activity was during the late 18th and early 19th century when this area was renowned for the production of tin ores, copper and a range of other metals and metalloids including arsenic, lead and zinc. During a period of hard rock mining tailings were habitually discharged into river courses adjacent to the mines and processing areas. The suspended solids, dissolved and particulate materials followed the course of these rivers into their estuaries where they precipitated out and formed a layer of contamination that remains to this day (Camm and Scott, 2003). Potentially toxic trace elements such as arsenic, copper, zinc and lead are therefore present at extremely elevated concentrations in some Cornish estuarine sediments. Whilst much of the contamination has been shown by previous authors to form a layer of contamination at depth within the sediment profile (Pirrie et al. 2002), re-working of the sediments by tides and biota means that concentrations at the surface remain high. Many of these estuarine soils provide a habitat in which the halophyte plant, Salicornia europaea, thrives. This species has been suggested in the literature as a potential candidate for phytoremediation.
Results presented in this paper reveal the geochemical fractionation of contaminants in samples of the estuarine soils where S. europaea is growing. The BCR sequential extraction technique, described by Rauret et al. (1999) and Sahuquillo et al (1998), was applied to determine to what extent certain potentially toxic trace elements are present in the easily available, reducible, oxidisable or residual pools of metals and metalloids within the sediment substrate. Concentrations of these elements were also determined in samples of S. Europaea and conclusions on the plant bioaccessible fractions of these potentially toxic trace elements are drawn. The implications for the management of these sediments and the impact of any proposed remedial measures to ameliorate contamination are considered in the light of these results.
References:
Camm, S. and Scott, P. (2003) Camborne School of Mines online virtual museum.
Pirrie, D., Power, M., Rollinson, G., Hughes, S., Camm, S. and Watkins, D. (2002). Mapping and visualisation of historical mining contamination in the Fal Estuary, Cornwall, online resource, Camborne School of Mines.
Rauret, G., Lopez-Sanchez, J. F., Sahuquillo, A., Rubio, R., Davidson, C., Ure, A., & Quevauviller, P., (1999). Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials. Journal of Environmental Monitoring, 1(1): 57-61.
Sahuquillo, A., Lopez-Sanchez, J. F., Rubio, R., Rauret, G., Thomas, R. P., Davidson, C. M., & Ure, A. M., (1999). Use of a certified reference material for extractable trace metals to assess sources of uncertainty in the BCR three-stage sequential extraction procedure. Analytica Chimica Acta, 382(3): 317-327.
The application of Point-Velocity Probes (PVP) for both groundwater velocity and groundwater-borne contaminant mass discharge quantification was investigated. The PVP is a novel method to directly measure groundwater velocity at the centimeter scale based on a small-scale tracer test (Labaky et al., 2007), and it has not previously been used to quantify aquifer-stream interactions or contaminant mass discharge.
In the spring 2014, 8 PVPs were successfully assembled and installed at the bank of Grindsted stream, located in the Region of Southern Denmark. The stream of around 10 m width and 1.7 m depth is impacted by xenobiotic organic contamination from two large contaminated sites, Grindsted factory site and Grindsted landfill, which are located 1.5 km north and 2 km south of the stream, respectively.
Numerous injection experiments were conducted in the 8 PVPs, as well as in 4 PVPs installed prior to this study. Horizontal flow directions pointed generally towards the stream, and average seepage velocities ranged from 0.3 to 2.5 m/d with standard deviations between 0.05 and 0.66 m/d.
The groundwater seepage velocities obtained from the PVPs were compared to those obtained from temperature profiling and Darcy's law. The Darcy-based seepage velocities were on average 6 times higher than the PVP values, which were in turn 10% higher than the temperature-based values. Differences may be related to scale differences of the methods, temporal variations as well as uncertainties in the estimates of geological parameters. This latter concern does not apply to PVP measurements, which are based on tracer transport times, making PVPs a useful addition to these kinds of investigations. The fact that the PVP-based seepage velocities fall in between those obtained from the other methods indicates that PVPs are capable of measuring groundwater velocity with an accuracy comparable to that of temperature profiling and Darcy's law.
The PVP-based seepage velocities were combined with groundwater contaminant concentrations to quantify the groundwater-borne contaminant mass discharge. Considering various scenarios, mass discharges for vinyl chloride (VC), benzene and total chlorinated solvents of 37-48 kg/y, 18 kg/y and 0.7-1.4 kmoles/y were found, respectively. Up to 80% of the contaminant mass discharge was found within 13% of the total contaminant plume width (hotspot). This indicates that contaminant plumes may be highly heterogeneous even in homogeneous sandy aquifers, hence fine-scale-monitoring is needed.
Observed contaminant stream concentrations of VC, benzene and chlorinated solvents were between 2.0-3.1 times higher than those calculated from the contaminant mass discharge. This suggests an underestimation of the mass discharge, likely caused by large spatial variations in groundwater velocity and contaminant concentrations.
In order to improve the estimates of the contaminant mass discharge, a second measuring round was carried out in the fall/winter 2014, including i) injection experiments in the 12 PVPs as well as in 2 additional PVPs, ii) multi-level measurements of groundwater contamination in a fine monitoring grid along the stream bank, and iii) slug tests along the stream bank. Preliminary results from the second measuring round support a highly focused discharge to the stream. It seems that a narrow plume embedded in a larger plume accounts for most of the contaminant mass discharge to the stream.
In conclusion, this study illustrates the high potential of PVPs for groundwater velocity quantification near streams, as well as for groundwater-borne contaminant mass discharge quantification. The results from the fall/winter campaign, in-depth interpretation of the field data and perspectives for contaminant mass discharge estimations at streams threatened by point sources will be presented at the conference.
References:
Labaky, W., Devlin, J. F., and Gillham , R. W. (2007). Probe for measuring groundwater velocity at the centimeter scale. Environmental Science and Technology. 41(24):8453-8458.
There are currently several methods used to determine the available fraction of organic contaminants in soils and sediments (e.g. mild-solvent extraction, Tenax extraction, cyclodextrin extraction, passive sampling, biosensors…). However, the comparison of these methods often shows discrepancies in the results, which underlines the need of a standardized method for availability measurement.
The aim of this study was to develop a new tool for the determination of the available fraction of organic compounds in contaminated soils. It consists in a thermodesorption – gas chromatography – mass spectrometry/flame ionization coupling (Td-GC-MS/FID). The idea is to link the binding energy between the compound and the matrix with the desorption temperature. In order to test the feasibility of such technique, polycyclic aromatic hydrocarbon (PAH) contaminated soils presenting various levels of contaminant availability were analyzed. For each PAH, the desorption temperature profile was compared to the efficiency of chemical (Fenton-like and KMnO4 oxidations) and biological (microbial incubation) treatments to degrade PAHs.
A gas plant soil, a wood treating facility soil and two coking plant soils were selected. One milligram of each soil was thermodesorbed at 10 °C/min from 100 °C to 800 °C according to the following temperature ranges: from 100 to 300 °C with six 50°C-steps, then from 400 to 500 °C and finally from 500 to 800 °C. The thermodesorbed compounds were subsequently separated by GC, PAH were identified by MS and quantified with the previously calibrated FID.
When considering one compound, the thermodesorption profiles of the studied soils exhibit differences in the thermodesorption temperatures. This observation highlights differences of PAH availability which were confirmed by comparing the efficiency of chemical oxidation and microbial incubation to remove PAH in the different soils. Correlation is observed between desorption temperature and treatment efficiency, the higher the concentrations of the compounds desorbed at high temperature, the lower the treatment efficiency and, consequently, the lower the availability.
The fine division of the temperature range allowed distinguishing between the measurement of bioavailability and the measurement of chemical availability. It is even possible to go further by differentiating between chemical oxidation treatments according to their efficiencies. In this way, the bioavailable fraction of the 2 and 3-ring compounds corresponds to the fraction desorbed up to 200 °C, for the 3 and 4 rings its correspond to the fraction desorbed up to 300°C and up to 250°C for the higher molecular weight PAHs. The lower desorption temperature for higher molecular weight PAHs is due to the recalcitrance of these compounds towards microbial degradation. The same classification was made for the chemical oxidation treatments. For the Fenton-like treatment the available fraction corresponds to the compounds desorbed up to 250 °C, 300 °C and 350 °C for the 2- to 4-ring compounds, the 4- and 5-ring PAHs and the 5- and 6-ring PAHs, respectively. For the KMnO4 oxidation, the available fractions of 2- to 4-ring compounds, the 4- and 5-ring PAHs and the 5- and 6-ring PAHs were desorbed at temperatures up to 300 °C, 350 °C and 400 °C respectively.
These preliminary results showed that Td-GC-MS/FID allowed linking different levels of availability to the PAH desorption temperatures and indicate that the Td-GC-MS/FID is a promising tool for a precise, fast and exhaustive determination of the available fraction of the organic compound in soils and sediments. This new tool could be used to target the most suitable treatment for the remediation of soils contaminated by organic compounds.
Eugen Martac, Axel Oppermann (Fugro Consult GmbH, Braunschweig, Germany)
Background: Applying Direct-sensing probes in combination with in-situ CPT (CPT: Cone Penetration Test) investigations have turned into powerful tools for the investigation of subsurface contamination, identification of hydraulic properties and exploration of natural resources. Originally developed by the U.S. Company Geoprobe, the Hydraulic Profiling Tool (HPT) is a system manufactured to evaluate the hydraulic behavior of subsurface soil. Using Fugro’s HPT sensors with extended capabilities on a CPT basis proved to have outstanding capabilities when it comes to delineation of the hydraulic structuring of highly permeable subsurface media and providing information about structure and setting up of the lithology simultaneously in just one push.
Methods/Activities: In order to deal efficiently with the in-Situ evaluation of the subsurface hydraulics, a new CPT-based HPT investigation probe was originally developed and is presently in use in Germany by Fugro Consult GmbH. The tool is advanced through the subsurface while water is injected at a constant rate through a screen on the side of the probe. An in-line pressure sensor measures the pressure response of the soil-groundwater system to water injection. Both pressure and flow rate are logged versus depth. The pressure response identifies the relative ability of a soil to transmit water. The water flows into the layers in an easier or more difficult way, depending on the hydraulic properties of the medium. The interpretation provides in a preliminary stage a relative profile of hydraulic conductivity. By means of several slug tests the results are site-specifically translated into absolute values of hydraulic conductivity. The probe extends the initial application domain (up to around 1 – 2 x 10-4 m/s) into to high permeability subsurface media (10-3 m/s) while being able to inject water up to 4000 ml/min.
Results: The irregular distribution of the contaminants is governed by the particular site hydrogeology and hydraulics. When the lithologic and hydraulic features of the site as potential migration pathways are identified, the spatial extension of the contaminant body within the source area and, by means of control planes, within the plume may be delineated. The developed site model delivers the key governing parameters in choosing the appropriate remediation methods for every discrete region of the site. The mass fluxes within the plume could serve as later monitoring device of the eventual success of different remediation options tested at the site.
Conclusion: The method allows a quick, continuous and in real-time profiling of soil hydraulic characteristics. Its applicability is not limited from the hydrogeological site particularities, being able to produce valuable information in both fine- and coarse-grained sediments under unsaturated or saturated conditions. Such high-resolution investigation method yields a solid basis for 3D site characterisation as lithological and hydraulic mapping of the underground.
Israel lies in an arid region with water shortage. An essential demand for this country is a high percentage of reused waters to cover water demand and protect water resources. Due to the water deficiency a lot of measures have been taken to ensure the water supply. Soil Aquifer Treatment (SAT) on Shafdan site near Tel Aviv is characterised by highly variable hydraulic conditions in the soil due to temporary infiltration of spreaded water. Pretreated wastewater flows in dry-wet cycles in several basins, which are filled within approx. 1 day. The water in the basins drains away within 12 hours and therefore the water content and moisture tension in the subsurface vary in dependency of the flooding intervals. During percolation, dissolved organic carbon (DOC) is diminished by 90%. The processes responsible for this enormous elimination are still widely unknown. Possibly the aerobic biodegradation could play a role but the proof is lacking. Many parameters of the soil water (redox potential, oxygen concentration, etc.) are usually influenced by the actual hydraulic conditions in the soil. However, no continuous physical or chemical analyses of Shafdan soil water have been available so far, due to the lack of a sampling technology. Therefore, a sampling procedure was developed in a unique 6 m laboratory column, which allows a representative sampling. The column was filled with soil from Shafdan site. It consists of 6 equal modules (1 m long each). Two samplers (suction probes) were installed in each module of the soil column (= 12 probes). Additionally, tensiometers installed nearly in the same layer can determine current moisture tensions. The resulting values are used for steering the vacuum at the suction probes. The preselected pressure difference between current soil tension value and vacuum pressure at the probes enables constant soil water sampling during all phases of percolating water plume and variable soil water contents.
This new method will allow representative sampling in different soil levels and thus help understanding the processes occurring in the subsurface.
BACKGROUND:
Investigating contaminated sites has traditionally involved drilling and collecting soil and groundwater samples for chemical analysis. This technique is both time consuming and expensive, and in most cases a number drilling sequences are required before the investigation is concluded.
Due to a growing number of contaminated sites, the European Commission has funded development of a new faster and dependable methodology for investigating contami-nated sites: Methodology for fast and reliable Investigation and Characterization of Contaminated Sites - or in short, the MICCS Project.
The MICCS Project has been through two project phases; first the development phase of the technologies, and secondly a demonstration phase, where the new system was demonstrated on contaminated sites formerly described by traditional Site Investiga-tions (SI).
The development of the MICCS Projects technics and concept was conducted by a European consortium of universities, technology institutes and private companies and is partly funded by EU FP7 grants. Project partners also developed software for con-trolling the MICCS probe, logging results, visualising the online sensor results in 3D models on laptop and calculating concentrations of contaminants.
AIM:
One of the aims of the MICCS system is to give a more comprehensive description of the contaminants, their concentrations and migrations in the soil and groundwater. This should results in less required certified analysis by laboratories - with a faster turn-around time and less expensive costs, and at the same time improve the quality of the SI.
Therefore, it is the intention of the project to achieve acceptance by the regulatory authorities in the EU to substitute the major part of the required traditional certified laboratory analysis with the MICCS sensor readings.
Another aim of the demonstrations is to verify that the sonic drilling method itself re-sults in an increased release of the volatile contaminants from the soil and groundwa-ter matrices. This should results in identifying lower concentrations.
THE MICCS CONCEPT:
The MICCS concept consist mainly of two phases of the field site investigation: First, the contaminated site is surveyed by a refined system of Ground Penetration Radar (GPR) and resistivity measuring methods (tracer), which identify underground installa-tions (pipes, UST, etc.), and gives a first indication of the areas contaminated at the site. Main geological features are identified also. For further explanation, please see http://miccs.eu
Second phase of the field investigation is utilizing a new probe technology with newly developed state of the art, highly sensitive sensors for volatile organic components - compound specific.
The MICCS probe system is designed for use with fast sonic drilling. The sonic drill-ing/probing required development of a new design to protect the components during the sonic g-force loads.
The probes sensors are during sonic drilling/probing through the soil profile able to continuously identify and measure concentrations of specific volatile compounds. These results are shown real time on a PC, which allow the operator to determine the type and concentration of volatile contamination at the drilling/probing location. Thereby allowing optimization of the planning of additional drilling/probing locations to fully describe the migration of contamination in the soil, groundwater and soil air.
The real time results of the type and concentrations of contaminants allows a compre-hensive investigation of the site in first field round, and ideally results in a 3D model describing the site geology, underground installations along with the contamination bodies.
DEMONSTRATION AND DOCUMENTATION:
After completion of the development phase, which included two field test in 2013, the demonstration phase included field demonstrations of the MICCS system/concept which were conducted during 2014 at different locations in Denmark.
By systematic comparison of the results of the MICCS system with the results of the conventional analysis, we have been able to demonstrate better and more compre-hensive results for describing contaminated sites.
The demonstrations show good correlation between the MICCS investigation results and the results of the traditional SI performed at the same sites. In general, the MICCS measurements show significantly better sensitivity than the traditional soil sampling with accredited analyses for the most frequent types of contaminants. The MICCS de-tection limits for these compounds are often more than ten times lower than the ac-credited measurements.
CONCLUSION:
Investigations conducted with the MICCS system will not only be faster, but also much more detailed than conventional SI methods. In addition, on-site work will be com-pleted continuously in one workflow, and the volume of required laboratory analysis can be reduced, as the advanced sensors in the probe produces very reliable results.
Public Funding Scheme for Remediation Projects in Austria
Following the estimation of the Federal Environment Agency Austria there are over 67.000 potentially contaminated sites in Austria, 7,5 % are to be considered waste disposal damages whereas 92,5 % are old industrial sites. Out of these it is estimated that 2.000 sites finally need remediation requirements at predicted costs of 5 to 6 Billion Euros.
The goal of the Austrian government is to remediate these damages within two generations. This is a very ambitious goal, which needs to be based on a solid financial aid system that encourages voluntary measures for the implementation of remediation projects.
The legal basis for the Austrian governmental aid consists of 4 different guidelines:
- Guideline of the European Community for governmental aid
- Law on Remediation of Contaminated Sites (ALSAG)
- Law on the aid of Environmental Protection (UFG)
- Guidelines for financial aid for remediation projects (Versions 1991, 1997, 2002 and 2008)
The most important law is the ALSAG, because it comprises the regulation of how to receive revenue for financing the Austrian subsidy system: a fee needs to be paid for every ton of depositing or burning waste, also for exporting (Austrian) waste. This law was implemented in 1990; since then the income can be indicated with 1,24 Billion Euro - for the issue earmarked money.
But not every remediation of a contaminated area can be financed by this aid. Substantial health-related and environmental risks must be proven, which means that the site must be registered in the “register of contaminated sites”- regulation after a profound analysis (risk-assessment) carried out by the Federal Environmental Agency. All registered sites will receive a priority assessment (ranging from 1 to 3), which stresses the importance and urgency of implementation of measures. These priorities also define the percentage of funding rate for the costs of a remediation project, which can be received.
For receiving funding the whole remediation phase must follow a strict and predefined process:
First an analysis has to be carried out in order to verify if the contamination was caused before 1st of July 1989 (a requirement set by the ALSAG-law).
After establishing this fact it must be verified by a cost-benefit analysis for different technical options that the implemented remediation or safeguarding project will achieve the greatest possible ecological benefit related to (macro-economically) justifiable expenses by the proposed technical implementation. Together with the aspired implemented variant the reduction or removal of the substantial health-related or environmental risks (the affected subject of protection) must be verified. The next step will be a reliable cost-estimate, which has to be submitted to the managing body of the Austrian Ministry of Environment, together with several application forms.
Fulfilling all statutory provisions and passing a commission, that gives a recommendation to the federal minister of environment of funding remediation projects, a percentage of costs ranging from 55% up to 95% can be reimbursed, depending on the defined priority of the remediated site.
Following this procedure since 1990 for about 170 contaminated sites remediation measures have been set and funded with public means in Austria. The average funding rate was about 77 %. In this context it can be mentioned that excavation is still the most common remediation technology, followed by sub-soil containment and combinations of pneumatic and hydraulic techniques.
During the last 25 years also 36 research projects were funded. Actual focus is given to research projects investigating the possibilities of nano-technology on one hand and projects combining chemical and biological in-situ technologies on the other Hand.
If Austria wants to reach the target to complete all required remediation in 2050 the common practice needs to be changed and improved. In 2010 a revision of the process and goals was started. Now the focus is on creating a new additional law, a uniform practice- and material law for the whole field of contaminated sites. The remediation targets should then be site- and land use specific. In addition the development of innovative and cost-efficient remediation technologies is encouraged and a focus is set on research and demonstration projects.
Why a National Remediation Framework?
The federal nature of Australian governance means that responsibilities are split between federal and state governments. Constitutionally, land management and environmental protection lies with the states, and differences have arisen in the management of these matters across the continent, due partly to disparities in geology, soil types and biota.
As the shift to a ‘seamless national economy’ continues (in parallel with globalisation), there is a drive to harmonise law, regulation and guidance across states, with significant benefits for the national economy. This also applies in environmental protection, and a Federal-state ministerial body has developed legally mandated, harmonised national environmental standards, including national guidelines for the assessment of site contamination. Legal and political realities have meant that to date, complementary national guidelines for remediation and management of contaminated sites are not in place – states each have their own guidance for remediation and management – which differs from one state to another, both in approach and in coverage of issues.
The comprehensive National Remediation Framework will promote cost effective and efficient site clean-up and management, and will facilitate enhanced standards of professional practice across the country. Where relevant the Framework will harmonise existing practice, and will not impinge on the decision-making prerogatives of the states.
The Framework and sustainability
The Framework will facilitate optimisation of the environmental, economic and social footprints for remediation and management. To this end, risk based land management (including the management of source-path-receptor links) and sustainability concepts underpin the Framework, consistent with state and federal environmental protection legislation.
Delivery
The Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE) is funded by government and industry, as well as research providers, to carry out mission oriented research into the clean-up of contaminated sites. CRC CARE’s remit also includes the development of regulatory guidance, premised on its credibility with all sectors and its access to government and industry expertise.
A steering group provides strategic oversight for the development of the Framework, and comprises stakeholders from the petroleum and mining industries, the Defence Department, land development agencies, contaminated land contractors consultants and auditors, and state environmental protection agencies, as well as community representation.
Framework structure and progress
The Framework comprises the following elements:
Part 1: Philosophy
• Context: background and jurisdictional arrangements, as well as purpose and intended audience
• Principles: consistent with ecologically sustainable development and sustainability
Part 2: Practice
• Guidance: practical guidance for practitioners relating to all steps of remediation and management - from the setting of remediation objectives to development and implementation of site remediation plans to post-remediation auditing and the use of institutional controls for longer term management.
Part 1 has been completed, and the development of Part 2 is well underway. It is expected that governments will endorse the completed framework.
Sustainable remediation optimises the social, environmental and economic value of the work. In the context of risk based contaminated land management, it involves achieving the necessary risk reduction. Sustainable remediation assessment is the final part of the process of deciding a site specific remediation strategy. It involves comparing short listed strategies any of which could achieve the desired risk reduction within a specific legal and policy context..
A document drawing together a worldwide consensus on the nature and process of identifying sustainable remediation on a site specific basis is being developed by a working group under the auspices of the ISO technical committee on soil quality (ISO TC190/SC7/WG12).
A committee draft was submitted in September 2014 and the working group are developing a Draft International Standard that takes on board comments received from National Standards Boards.
[The final abstract and paper will include the outcomes of reflecting on these comments.]
Abstract Aquaconsoil 2015 - Lake Boyuk Shor: environmental engineering and eco-hydrology as fast track to engineering solutions for lake restoration in Azerbaijan
B. van der Enden1, R. Dijcker1, D. de Kramer1 and G. Kruitwagen1
The lakes situated around Baku, the capital of the Republic of Azerbaijan, are ecological and environmental heavily impaired. For 9 lakes a Feasibility study on the remediation options was performed, creating a target for future developments and policies. For the largest lake this momentum is directly effectuated by implementing the proposed remediation options before June 2015. What has been the approach from available data to a full scale lake remediation within the given time constraint?
Economic prosperity resulting from oil industry has been the driving factor behind the rapid expansion of Baku, capital of Azerbaijan. The city has now expanded beyond the 9 lakes that lay in a belt around the city. The expansion of the city has increased the potential value of the lakes, which is at present limited by severe pollution. The lakes have been neglected for a long time as a result of the orientation of the city towards the Caspian Sea. As a side-effect the lakes have become a dumping ground for oil products, sewage, and solid wastes. The Ministry of Economy and Industry of the Republic of Azerbaijan is now making a major effort aimed at the remediation and rehabilitation of the lakes.
In spring 2013 an assessment of the feasibility of remediation and rehabilitation of the 9 lakes was started. The focus of the feasibility study was on system analysis: getting an understanding of the key factors and processes in the functioning of the lakes in the Baku area. The complex pollution was unravelled including identification of its sources resulting in a conceptual site model for each lake. Based on an economical cost-benefit analysis remediation scenarios are developed and assessed.
In autumn 2013 the efforts were focussed on the remediation of the Boyuk Shor lake. The remediation aims at development of social and economic potential of this part of the city in the vicinity of the lake. The lake will also form the decor for the first European Games, to be held in June 2015. To serve this combination of long-term restoration goals and short term functionalities a detailed design for rehabilitation of the lake was made. The conceptual site model and remediation scenario development were used as powerful tools to identify key measures for the remediation and structure the restoration efforts. At present the restoration of 250 hectares of the lake is already in full swing: a direct result of the multidisciplinary approach in which hydrology, ecology, environmental remediation and hydraulic engineering are interwoven to get from feasibility study through design and engineering to realisation within 2 years.
Keywords: brownfield redevelopment, ecological lake remediation, environmental hydraulic engineering, Azerbaijan, feasibility study, cost-benefit analysis.
1 Witteveen+Bos
Still today river sediments can be contaminated with persistent chemicals (PCBs, dioxins, mercury) leading to exceedances of food threshold levels in fish. Environmental risk assessments of contaminated rivers exhibit multiple challenges: Often primary sources do not exist anymore (e.g. ancient sewers) or are initially not known (e.g. uncontrolled landfills next to rivers). In addition, contaminant inputs often occur via multiple pathways (sewers, tributaries) and diffuse emissions (surface run off from infrastructure systems). Back-contamination from secondary sources can occur: Not only sediments but also river banks are often significantly contaminated because of deposition of contaminated suspended material from the river water.
Here we will present the elements of an environmental risk assessment, the development of remediation targets and remediation options for contaminated rivers by using an illustrative example of a Swiss drainage channel whose sediments were contaminated over a length of about 2.3 km: a) a sampling campaign using custom-made liner-in-liner technique for optimal performance under challenging environmental conditions, b) a risk assessment approach that i) prioritizes the contaminant sources on the basis of their input paths and release potential ii) and therefrom allows to derive feasible and sustainable remediation targets and iii) the selection of most efficient remediation options.
Sampling Techniques: Due to the low aqueous contaminant concentrations, river water was sampled with passive samplers. To overcome the challenges of sediment sampling at high streaming velocities, a liner-in-liner sampling system with a core-catcher based on a mobile platform was developed. The contamination of river banks and adjacent soils was assessed, because based on the available historical information, sediments were often excavated and deposited near the channels on agricultural and residential areas. These depositions can lead to back-contamination of the sediments and may represent a potential human hazard. Several tributaries such as sewers, rivers and run-offs (spillways) were included into the sampling campaign. In addition to the relevant contaminants, soil and sediment properties such as organic carbon content and grain size distribution were addressed, to account for the relevant phase partitioning processes in river systems.
Risk assessment: Based on the conceptual site model contaminant masses, mass fluxes and concentrations were mathematically described for individual sectors of the channel. Contaminant releases for the multiple pathways were predicted: transport via infiltrating rain water, erosion of contaminated river bank material, input of contaminated sediments and water via tributaries. The remediation targets were developed in a two-step procedure: in a first step, the tolerable contamination of the sediments was derived by calculating the tolerable bioaccumulation rate via the sediment-fish pathway. In a second step the tolerable remaining input of contaminants into the channel (tolerable “back-contamination”) was calculated and therefrom the tolerable concentrations in the river banks were derived. Remediation targets for an adjacent agricultural field were derived by calculating the tolerable uptake of contaminants by cattle during grazing, which was the most sensitive use of the land.
Remediation: The channel was remediated by excavation and replacement of the river banks and sediments in the relevant sectors to the relevant depths. For this, the water flow was diverted sector-by-sector and the contaminated material was replaced. As an ecological benefit fish niches were installed and gravel of different size was used for reinstatement of the river bed, to provide optimal conditions for different fish species.
In the construction phase of large infrastructure projects such as tunnels and hydropower plants thousands of tons of construction chemicals and explosives are used. These chemicals can cause substantial environmental hazards. However, these hazards are often not anticipated upfront of infrastructure projects because of the project’s complexity: The project areas are often widespread exhibiting several construction sites with construction activities over years and various protective goods that can be affected by contaminant emissions.
The use of ammonium nitrate-based explosives and organic boosters leads to emissions of ammonium, nitrate, nitrite and nitroorganic compounds to the environment. From the application of construction chemicals (sprayed concrete, retarders, slurries, hydraulic liquids, etc.), contaminants such as hexavalent chromium, aluminium, and various organic chemicals including biocides are released to the environment.
These compounds lead to negative effects in susceptible surface waters and used groundwater. Observed effects are general ecotoxicity to aquatic life, fish toxicity (nitrite, ammonia, Al3+aq), eutrophication (nitrate), inhibition of photosynthesis (turbidity) or oxygen depletion (by dissolved organic carbon).
The emission of the substances occurs via multiple pathways: Polluted excavated material is often deposited in or along surface waters because of space shortage in the project area. From there, contaminants and fine materials are released into the water during and after the deposition. A second important emission path are tunnel effluents that are discharged to creeks with partly low runoffs. Additionally, highly contaminated material such as sludges from material recycling are deposited in project-specific landfills in the project perimeter which can lead to additional emissions.
The flux of pollutants to protective goods and therefore the environmental risk is highly variable in time and location and depends on the construction activities at the multiple construction sites as well as the environmental conditions such as seasonal variability of precipitation (snow, rain), hydraulic discharges of rivers, water levels of lakes etc. To overcome these complexities, we have established a unique method for the identification of possible environmental hazards during the entire construction works. This method is based on a holistic analysis of all project phases and processes. The project system is represented by a mathematical model that predicts contaminant fluxes and concentrations as a function of time and space in all protective goods of concern. The predicted environmental concentrations (PEC) are compared to (eco)toxicologically based reference levels (predicted no effect concentration, PNEC). This risk assessment method has already successfully been applied in several Swiss projects.
The benefit of this upfront environmental risk assessment is to anticipate possible hazards already in the planning phase of the project as an integral part of the environmental impact assessment. The risk assessment allows the identification and prioritization of the relevant processes, time points and locations, which potentially lead to critical environmental impacts. These procedure guarantees the implementation of risk reduction measures and hence investments at locations with the highest impact. Such measures include installations (such as water treatment plants), application of best-practices (e.g. for the application of emulsion explosives) or the use of environmentally friendly products.
The presentation will give an overview on the method that allows for the holistic assessment of all contaminant emissions at all construction sites during the entire construction project. The strengths and limitation will be discussed as well as illustrative results from reference projects will be presented. The substances of concern, their sources and possible effects will be addressed.
The benefits of urban agriculture are many and well documented, ranging from health improvement to community betterment, more sustainable urban development and environment protection. On the negative side, urban soils are commonly enriched in toxic trace elements that have accumulated over time through the deposition of atmospheric particles (generated by automotive traffic, heating systems, historical industrial activities and resuspended street dust), and the uncontrolled disposal of domestic, commercial and industrial wastes. This in turn has given rise to concerns about the level of exposure of urban farmers to these elements and the potential health hazards associated with this exposure. Research efforts in this field have started relatively recently and have almost systematically omitted the influence of Sb and Se, and to a lesser extent of As, although all three have proven toxic effects.
In this study, the concentrations of aqua regia-extractable As, Sb and Se have been determined by GF-AAS in 42 soil samples collected with an Edelman auger from the upper 20 cm of the soil profile in seven urban gardens in Madrid. Soil physicochemical properties, i.e. soil pH, texture, calcium carbonate and organic matter contents have also been evaluated. Frequency and duration of exposure, and rates of consumption of vegetables grown in the selected urban gardens have been estimated from the results of an on-site survey. The mean concentration of As in the seven urban gardens is similar to regional background levels but the average content of Sb and Se are one order of magnitude higher, and in the case of Sb, exceeds the guideline value for agricultural land use in Madrid.
The risk for urban farmers from exposure to As, Sb and Se through four routes of exposure (accidental ingestion of soil, inhalation of suspended particles, dermal absorption and ingestion of vegetables) has been assessed. The quantitative results of the risk assessment are very sensitive to changes in the value assigned to two key variables that are affected by a high degree of uncertainty: soil ingestion rate and soil-to-plant uptake factor. For the values used in our model, taken from the USEPA’s Soil Screening Guidance and from the RAIS database, the highest contribution to the overall risk is associated with the accidental ingestion of soil particles, followed by ingestion of on-site grown vegetables and dermal absorption (inhalation of suspended particles has a negligible influence). However, changes in the soil-to-plant uptake factor within the range of published values for this variable can result in a contribution of ingestion of vegetables higher than that of soil ingestion, and in a different value of the predicted overall risk. It remains unaffected the fact that As is the contaminant of most concern given its carcinogenic nature. In terms of systemic toxicity, As is also the main contributor to the aggregate Hazard Index, followed by Sb and Se.
The estimates of overall systemic risk are more than one order of magnitude lower than the threshold values of HI=1, but that of carcinogenic risk, associated with the exposure to As, lies in the range of 10-5 - 10-6, close or even above the limit of acceptability, depending on national environmental regulations. Although risk assessments make use of very conservative assumptions, these results indicate the need for further research in order to reduce the uncertainty in some of the variables included in the model and to dissipate the concerns regarding the potential for adverse health effects associated with the practice of urban gardening.
Gardening is fun and healthy. No bigger pleasure than to harvest and eat one's own vegetables, to raise chickens and eat their eggs. Local food production has many other advantages: it contributes to a sustainable lifestyle, increases social cohesion, ….
However, in some cases, there are concerns about the presence of pollutants in home-grown food and eggs. In Flanders, with its long industrial history and high population density, diffuse soil contamination is widespread, especially in urban areas. Diffuse soil pollution cannot be linked directly to a source, and is due to all kinds of, sometimes very small, activities in the past, such as waste burning and disposal.
The presence of pollutants in home-grown food is shown in several studies, such as those resulting from the Flemish human biomonitoring program (2001-2006), and the study 'Dioxins in eggs and vegetables of private gardens' (2011). Especially with regard to the increased levels of dioxins in eggs of home-raised chickens there is a matter of concern.
How can we ensure that people can eat their home-grown vegetables and eggs from their own chickens without having to worry about their health? Together with the Service Health and Environment of the Department LNE, the OVAM sets up a system to provide suitable advice and information for citizens. The aim is not to discourage growing one's own food, but to reduce possible health risks by practical measures.
Practical guidelines are provided on how to grow vegetables and to raise chickens in allotments and private gardens in a safe way. For example, the guidelines include advices on the location of the garden in relation to heavy traffic, industry, historical contaminated sites, … When the quality of the soil is uncertain or questionable, the advice is given that one should test the soil for contamination, i.e. to take a soil sample and get it analyzed.
However, the cost of soil analyzes may be too high for private persons who are gardening for leisure. This is especially the case when one wants to raise chickens for egg production and soil testing for dioxins is needed. Therefore, on behalf of OVAM, Arcadis Belgium nv performed a feasibility study to look into the possibilities of setting up a system for soil analyzes at reduced prices. This study treats the organizational, financial and legal aspects, and includes as well an online survey of gardeners about their concerns related to soil contamination, their willingness to pay, … As part of the feasibility study, a pilot project is set up in collaboration with a local authority. In this community, soil testing at a reduced price is offered for private gardeners during a test period.
In support of previous actions, VITO developed a framework for the interpretation of the results of the analyses. For the most important pollutants, reference values were calculated for concentrations in soil that allow growing food products without health risks. The model S-Risk was used to calculate these values. With this model it is possible to define different scenario's, and to take into account the exposure route by consumption of home-grown eggs.
The advice and information system for gardeners is part of a more general approach for the management of diffuse soil contamination. This type of soil contamination is not always covered by regulation. In these cases, OVAM focuses on the avoidance of risks for human health due to diffuse soil contamination.
Abstract:
Cumene – or isopropylbenzene - is a volatile aromatic hydrocarbon with an odor threshold below the chemical-analytical detection limit. The soil contamination with cumene was caused by a road accident in which a truck loaded with Komol fell over and 10,000 l of Komol – with cumene as the principal compound - poured out all over the soil surface. In 2012, soil investigation showed:
• a soil contamination – source location – of about 750 m2 until 7 m below ground level
• a ground water contamination up to 350 m from the source location and to a depth of 25 m below ground level.
The Dutch province of North Brabant – the ‘problem owner’ - was confronted with many questions. How to assess the risks of this compound for which no general risk assessment for soil contamination exists? How to translate risk levels into remediation goals? What remediation approach will abolish all odor nuisance for the residents of the location? How to prevent nuisance during the remediation activities (as much as possible) and how to protect the health of the residents and contractor’s laborers? The province of North Brabant had to address these and many other questions in such way that the final aim of the remediation would be achieved in the most effective way and with respect to the complex situation with many stakeholders involved.
The presentation on Consoil will show the results of the investigation (conceptual model), risk assessment, in-situ remediation measurements and the applied process of a building team construction, which have resulted altogether in a successful remediation.
The soil and ground water investigation has based on a conceptual model, which gave insight in the information gabs, research questions to be answered and a clear visual insight in the contamination. The risk assessment consists of two levels: technical risk assessment concerning the human and environmental risks of the contamination and risk management (using the RISMAN method) to clarify and to address properly all project related risks. One of the most important issues of the technical assessment is the impact of the extremely low odor threshold level on the remediation goals to be achieved and the remediation activities needed to secure these goals. The conceptual model mentioned above and risk management have been the starting points of the project approach and project risks are determined and prioritized by the stakeholders involved, e.g. extreme odor nuisance, conventional explosives (second world war) and groundwater extraction. In 2012, an evaluation of the most appropriate contract form and market analyses followed the risk management session hold and as a result the building team construction has been chosen as the best suiting contract form and a short list of contractors was generated who were invited to compete for the contract. Furthermore, the advantages of the building team construction will be shown:
- the province of North Brabant is able to influence the process in such a way that the province can take its responsibility in this complex situation in which residents are involved
- members of the team (province, consultant Tauw and contractor NTP) depend on each other for the realization of the project and project risks are addressed and solved in the most effective way possible
Finally, the remediation consists of both excavation activities and in-situ measurements. The possible in-situ remediation measurements – biological, fysiological and/ or chemical - have been evaluated and it has been decided to implement a bioscreen to remediate the ground water contamination and to imply a bio blanked with a slow release compound on the floor of the excavation.
At many sites contaminated with hydrophobic organic chemicals such as polycyclic aromatic hydrocarbons (PAH), it has been observed that a fraction of pollutants sequesters with time, thus remaining unavailable for biodegradation. In addition, residual tar oils containing PAH are often dumped combined with small grain size waste coal and coke materials from processing at former gas work sites. In order to find suitable solutions for improving the biodegradation potential at the respective sites, predictions can be provided for the consequences of altered conditions for microbial growth and degradation. For optimisation of the remediation strategies and for interpreting observed effects, a combined model was applied for simultaneously considering dissolution from an organic chemical phase (non-aqueous phase liquids or solids), ad/desorption, sequestration (aging), microbial metabolism and growth, and the formation of non-extractable residues. The model has been verified from experimental observations in various aspects (Marchal et al. 2013, Kästner et al. 2014, Adam et al. 2014; see also presentation of Rein et al. on dissolution and microbial degradation of different PAH, at AquaConsoil 2015).
This model was used for the simulation of bioremediation options for clean-up of PAH-contaminated soils. The objectives were to understand the behaviour of PAH compounds in contaminated environments and to give recommendations for bioremediation measures based on this knowledge. We analysed the turnover of PAH by combining ad/desorption models for organic compounds with models for the growth and degradation kinetics of microbes. We modelled several scenarios and interpreted the observed effects, such as increasing distribution coefficient (Kd) and persistence of the PAH with time, decreasing degradation rates with concentration, and effects of amendments on sorption and degradation. Based on the kinetics of the processes and the fluxes in the system, we can provide a robust mathematical definition of the terms “bioavailability” and “bioaccessibility”. Finally, the model was applied to evaluate the most effective remediation strategy for PAH contaminated soils and sediments.
The modelling results indicate that added degrader bacteria only remove substrate for a short time-period. The addition of sorbents may decrease the bioavailable fraction. This results in lower plant uptake and toxicological risk, but may increase the persistent residual fraction. The persistence of a compound in aged soils can be overcome by increasing the desorption flux (e.g., by detergents or solvents e.g. acetone) and by stimulating bacterial growth by amendment with complex co-substrates (compost, root exudates). In addition, substrate affinity is an important factor for the competitiveness of bacteria in microbial communities under varying environmental conditions and in particular for varying available substrate abundances. It will thus finally determine the community structure at contaminated sites in general and particularly how the microbial community structure is affected by remediation measures.
Marchal G, Smith KE, Rein A, Winding A, Wollensen de Jonge L, Trapp S, Karlson UG. 2013. Impact of activated carbon, biochar and compost on the desorption and mineralization of phenanthrene in soil. Environ. Pollut. 181, 200-210.
Kästner M, Nowak KM, Miltner A, Trapp S, Schäffer A. 2014. Classification and modelling of non-extractable residue (NER) formation of xenobiotics in soil - a synthesis. Crit. Rev. Environ. Sci. Technol. 44 (19), 2107 - 2171.
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.
Rein A, Adam IKU, Miltner A, Fulgêncio ACD, Brumme K, Trapp S, Kästner M. 2015. Impact of low-soluble hydrophobic substances on microbial turnover – Integrated modelling of microbial growth, degradation and dissolution from organic phase. Presentation at AquaConsoil 2015.
The microbial diversity linked to ETBE and TBA degradation in an ETBE-polluted aquifer was assessed by means of an integrated culture dependent/independent approach. Bench scale microcosm studies, isolation of ETBE/TBA degrading strains and microbiome analysis of native microbiota both in microcosms and in-situ stimulated groundwater were performed.
ETBE degrading strains were isolated directly from polluted groundwater (piezometer P11 and well W29) and from ETBE-degrading microcosms constructed from non-stimulated P11 groundwater. The obtained isolates were able to grow on mineral agar supplemented with vitamins under a saturated ETBE atmosphere as the sole source of carbon and energy. On the basis of colony morphology and 16S rRNA gene sequence, five strains were identified (ETBE-3 and ETBE-10 (belonging to Rhodococcus erytrhropolis), ETBE-8 (Sphingopyxis sp.), ETBE-11 (Hydrogenophaga pseudoflava) and ETBE-16 (Gordonia sp.) and selected for subsequent ETBE and TBA biodegradability assays. Three of the five strains (ETBE-3, ETBE-10 and ETBE-16) were able to degrade ETBE, whereas ETBE-8 (Sphingopyxis sp.) and ETBE-11 (H. pseudoflava) were only able to degrade TBA in batch assay conditions. The strain ETBE-16 was able to degrade both ETBE and TBA, but a transient accumulation of TBA was observed at early incubation stages. The synthetic consortium formed by the combination of the five strains was able to degrade 100 mg/L of ETBE in 5 days, without any transient accumulation of TBA. The co-culture of strains ETBE-16 and ETBE-11 was also able to prompt the complete ETBE biodegradation with no TBA occurrence during ETBE degradation.
In order to ascertain the environmental relevance of the isolated ETBE/TBA degrading strains, the microbial communities naturally occurring in groundwater samples and responding to microcosm incubations were analyzed by next generation sequencing (NGS). 16S rRNA gene-based 454-pyrosequencing from total Eubacteria was applied to i) initial groundwater (P11), and wells W23 and W29, before and after in-situ aerobic stimulation, and ii) microcosms from P11, which were aerobically stimulated with different N and P sources. The results showed that the microbial community structure from the groundwater (P11, W23 and W29) after the implementation of in-situ stimulation strategies was clearly different from the pre-existing microbiota. The predominant phylum in polluted groundwater prior to biostimulation (P11 and W23) corresponded to Proteobacteria with a relative abundance above 90% of the total population, being mainly composed by representatives of the Pseudomonadaceae family (Gamma-Proteobacteria). Members of the classes Alpha- and Beta-Proteobacteria, as well as from the phyla Bacteroidetes and Actinobacteria were also predominant in samples P11, W23 and W29 and in the microcosms. Multivariate correspondence analysis based on OTUs closely related to known ETBE/TBA degraders described in literature revealed a significant association of OTU 18 with ETBE exposed microcosms and non-stimulated groundwater (P11 and W23), but was not detected after in-situ biostimulation. Interestingly, OTU 18, accounting for 0.4% and 1% of the total community present in samples W23 and P11, respectively, was identical in sequence to the ETBE degrading isolates ETBE-3 and ETBE-10 and was highly homologous to the type strain of Rhodococcus erythropolis. After in-situ bioestimulation OTUs linked to other Actinobacteria, such as Arthrobacter spp. or Mycobacterium spp., became more predominant. In this sense, it is noteworthy that only one OTU closely related to Gordonia (strain ETBE-16) could be detected in W23 at late stages (t2) after in-situ biostimulation.
NGS results combined with microcosm studies and isolation of degrading strains revealed important shifts on the microbial community structure and the diversity of potential ETBE/TBA degraders affected by biostimulation strategies.
Coal tar, or creosote, as a by-product from coal gasification in municipal or manufactured gas plants (MGP), has been used for numerous industrial purposes including wood impregnation or preservation and as a raw material for a variety of commodity products. Being initially valued for its antibiotic properties, the constituents of coal tar, where released into soil and groundwater, now pose a considerable threat to soil and especially aquatic resources in many industrialized countries.
Coal tar is a complex mixture; its aromatic and phenolic constituents are considered the most worrisome from an environmental viewpoint. A comprehensive understanding of abiotic and enzymatically mediated pollutant transformation processes, involving complex contaminant (= tar oil), geochemical (= soil and aquifer mineral inventory) and microbial matrices (= mixed archaeal and bacterial communities), is required to control and, if desired, enhance biogeochemical reactions that contribute to the breakdown of organic contaminants.
In this context, one of the geochemical aspects less well understood is the role of poorly water soluble minerals that may serve as terminal electron acceptors (TEA) in anaerobic contaminant oxidation, including Fe(III) and Mn(IV) minerals, in hydrocarbon-contaminated aquifers. Despite their poor aqueous solubility and thus poor bio-accessibility, these mineral species participate in microbe-driven geochemical cycles. Several mechanisms, including electrochemically conductive pilus-like assemblages expressed by Geobacter species, or Shewanella’s chelating agents, enable for extracellular electron transport to practically insoluble Fe(III) and Mn(IV) surfaces serving as TEA in contaminant oxidation, have been ‘devised’ by nature.
The present study sets out to investigate artificial substitutes to these species-specific mechanisms to increase extracellular electron transfer processes connected to potential benefits for anaerobic contaminant oxidation. These extracellular electron shuttles (EES) are small organic and reversibly reducible/oxidizable structures that may participate in a large number of consecutive reduction and re-oxidation, driven by or in the absence of microbes. Both laboratory- and field-scale studies were performed.
Potential extracellular electron shuttles were characterized in laboratory trials using historically tar-oil contaminated soil and aquifers in terms of their efficiency to mediate the anaerobic oxidation of aromatic hydrocarbons, with a focus on EPA-PAH, N-, S- and O- substituted heterocyclic compounds as well as alkylated PAH. Contaminant transformation was monitored using GC-MS and comprehensive GCxGC-MS. The addition of various investigated structures, predominantly humic model substances (Quinones) in substoichiometric quantities were found to significantly increase biochemical and, to a lesser extent, abiotic contaminant oxidation in anaerobic bioreactors. A decrease in PAH concentrations was found to occur in parallel to an increase in aqueous-phase Mn and Fe-contents. These data suggest that using EES, a certain, soil or aquifer-specific poorly crystalline fraction of reducible Mn- and Fe-minerals are being made available to PAH-degrading organisms using EES. This fraction was predicted by incubating soil and aquifer samples with Shewanella alga and an easily accessible source of carbon and energy.
A small field trial was implemented in a microbially active, anaerobic tar oil contaminated aquifer with a high predicted Mn (IV) - availability. There, the increase in aqueous Mn- concentrations in the wake of the addition of a non-toxic EES into the groundwater points towards the possibility to stimulate electron transfer to poorly soluble geogenic terminal electron acceptors connected to the anaerobic oxidation of PAH. The analysis of ground water samples using GCxGC-TOF-MS revealed a qualitative change in hydrocarbon inventory and an enrichment in tentative PAH degradation products during EES application, suggesting a link of Mn- reduction to PAH oxidation facilitated by EES.
The application of extracellular electron shuttles to increase anaerobic oxidation processes is a direct approach to exploit indigenous, poorly soluble electron acceptors and thus represents an environmentally compatible bioremediation measure.
From a molecular level, geochemical and biogeochemical transformation processes involving hydrophobic contaminants and poorly accessible electron acceptors in complex matrices remain largely unexplored.
Methyl tertiary-butyl ether (MTBE) is a synthetic car fuel additive. However, it’s widely use resulted in groundwater contamination (up to 830 mg/L) with MTBE. Tert-butyl alcohol (TBA), an intermediate in MTBE degradation, is often found in association with MTBE contamination. Both compounds are very mobile in the subsurface and are threatening drinking water winning areas. They are, however, difficult to treat with existing pump and treat technologies (air stripping; sorption on activated carbon) due to their low sorption tendency, high water solubility and recalcitrancy. However, more efficient innovative technologies exist, which comprise biotechnology.
GROUNDWATER TREATMENT: Earlier, an aerobic MTBE/TBA-degrading bacterial consortium (M-consortium) has been isolated and its use for treating MTBE/TBA-contaminated groundwater was demonstrated. An inoculated bioreactor for ex-situ MTBE/TBA-removal from groundwater, as part of a pump and treat solution, was developed at lab-scale and demonstrated successfully at pilot scale. The technology realizes not only improved MTBE/TBA-removal, but is also more sustainable and eco-efficient in comparison with alternative methods, as the technology focuses on the destruction of the pollutants and not a relocation to other compartments (air, activated carbon).
Within the FP7 MINOTAURUS project (EU GA 265946) the robustness and reliability of biotechnologies like the inoculated bioreactor was investigated, which is important to come to innovation, being the full scale applications. Earlier, results from lab scale tests showed (1) that bioremediation is a valuable option to remove MTBE/TBA from groundwater and (2) that the M-consortium has potential as bacterial inoculum to enhance MTBE/TBA and BTEX-biodegradation under aerobic conditions. Next, pilot scale tests were performed to evaluate the robustness and reliability of the system at larger scale under real conditions. The results of 2 pilot test in the field will be summerized.
Test site 1: A pilot scale inoculated bioreactor (300L) was operated in the field at an industrial in Belgium for about 5 months. The prototype bioreactor was shown to be a relatively fast starting and stable system, removing MTBE (300-5000 µg/L) and TBA (3500-10000 µg/L) from the groundwater in an efficient way, hereby meeting regulatory limits.
Test site 2: An improved filling material to retain the biomass in the bioreactor was selected and used for the second bioreactor test. Firstly, the reactor was uploaded off-site where data indicated a good performance of the system. Next, the system was transported and operated at a petrol gas station (Belgium) treating groundwater contaminated with MTBE and TBA.
DRINKING WATER: The quality standards for drinking water are stricter in comparison with groundwater. Within the MIRESOWA-project (Danish project) different partners were active to evaluate the potential of biotechnology for treatment of polluted drinking water resources. The basis of the proposed technologies was bio-augmentation. Besides pesticides, MTBE and TBA were among the pollutants considered. At lab scale, bioreactors inoculated with the M-consortium were tested to remove MTBE and TBA at conditions that are inherent to drinking water production processes, being lower concentrations and higher fluxes. The results showed that the inoculated bioreactor technology offers potential for drinking water as it was possible to reduce the MTBE and TBA concentration below the regulatory limit (20 µg/L) without the need for frequent inoculation of the system.
Anaerobic bio-oxidation uses alternative electron acceptors instead of oxygen to destroy petroleum based contamination. This process occurs naturally at nearly all petroleum hydrocarbon contaminated sites. Cases with engineered addition of alternative electron acceptors are limited, as anaerobic oxidation is perceived as a slow process. However, the increased knowledge of bioremediation and recent studies have revealed that this process is more rapid than previously perceived, and that it has some significant advantages over the use of oxygen for bioremediation of petroleum hydrocarbons. In particular, the use of sulfate has gained recognition recently due to its high solubility and the limited potential for reactions with the soil matrix. Further, the absence of requirement for an energy intensive extraction and treatment system is an additional advantage.
An intensive study on the degradation capacity of sulfate on two site in Belgium, contaminated with BTEX, is described. Both the natural degradation capacity of soil and groundwater and the effect of addition of sulfate were evaluated. At one site a pilot test wit sulphate injection was performed and monitoring results of 1 year indicated a significant decrease of groundwater contamination.
For this evaluation, the following investigation was executed:
• Analysis of geochemical parameters to determine the geochemical conditions
• Sulfur and sulfate soil analysis were performed to estimate the quantity of reduced contamination and the quantity of sulfate available for biodegradation
• Biotraps® were used as microbial growth media in monitoring wells and analyzed after exposure to the aquifer. The following tests were undertaken:
o Biotraps® were marked with C-13 labeled benzene to evaluate the degradation velocity of benzene, the formation of CO2 and C-13 uptake in biomass.
o Biotraps® were analyzed on bacterial composition with polymerase chain reaction (PCR) analysis
o The above tests were performed under natural conditions and with sulfate addition
• Field pilottest with injection of sulphate and monitoring of degradation during one year.
Based on the findings, a remedial strategy with natural attenuation and focused application of sulfate in the source zones was selected and was preferred to a remedial strategy with a resource and energy-intensive multi-phase extraction.
The general principles of the technology and the investigation results of the case studies including the pilot test results will be presented.
Chlorinated solvents, such as trichloroethylene (TCE) or perchloroethylene (PCE), are among the most common groundwater pollutants. TCE and PCE often exist in the subsurface as dense non-aqueous phase liquids (DNAPLs), which serve as a source of long-term contamination. The inefficiency and high cost associated with the conventional remediation methods to remove DNAPLs led to seek for alternative ways of remediation, which accelerate the rate at which contaminated sites are restored back to an acceptable condition, and thereby reduce the cost of remediation. Probably the most attention in recent years is focused on the in situ chemical reduction using nanoscale metallic iron (Fe0), also referred to nanoscale zero valent iron (nZVI). The technology involves corrosion of Fe0 which provides the electrons necessary for the reduction of compounds such as chlorinated solvents. In aqueous solution, nZVI reacts with water and oxygen to form outer layer consisted of iron oxide/hydroxide. The accumulation of the corrosion products on Fe0 surface can affect reduction either by inhibiting contaminant access to the metal surface or by forming new sites for contaminant adsorption, reaction, and catalysis to occur.
Iron has long been recognized as physiological requirement for life of many microorganisms that persist in water, soils and sediments. Several iron reducing bacteria use Fe(III) oxyhydroxide and iron oxides as terminal electron acceptors under anaerobic conditions. These dissimilatory iron reducing bacteria (DIRB) that are widely distributed in the subsurface may play an important role in enhancement reductive treatment by nZVI. Hydrogen which is catholically produced during anaerobic corrosion of Fe0 can stimulate anaerobic bioremediation by serving as electron donor for the biotransformation of reducible contaminants. Moreover, DIBR could enhance the reactivity of nZVI by reductive dissolution of Fe(III)-oxide layers and formation of reactive minerals such as green rust and magnetite.
The aim of this study was to investigate whether DIRBs are able to utilize Fe(III) on the surface of nZVI and thus enhance its reactivity. Furthermore TCE removal by three strains of DIRBs was examined using different sources of Fe(III) including nZVI. Batch experiments using 120 mL serum bottles containing artificial groundwater, real groundwater and soil were used. The batch experiments were conducted in dark, at 12°C, and bottles were shaken using horizontal shaker. The bacterial concentrations were obtained using the most probable number method. Fe(II) and Fe(III) were analyzed using Ferrozine test, and head space analysis of TCE was performed on gas chromatograph/ mass spectrometer. Furthermore pilot test on a site contaminated by chlorinated ethylenes was conducted.
Experiments showed that tested DIRBs had sufficient microbial activity to reduce Fe(III) on the surface of nZVI. The experimental results also showed that DIRBs were able to degrade TCE in the condition of natural groundwater, however, did not improve the reactivity of nZVI.
ACKNOWLEDGEMENTS
This work was financially supported by Technology Agency of the Czech Republic, project number TA02020654.
Innovative Nature of the Topic.
Both enhanced reductive dechlorination (ERD) and in situ chemical reduction (ISCR) have emerged as cost-effective remedial approaches for groundwater with elevated concentrations of chlorinated solvents or heavy metals. ERD involves the addition to groundwater of an organic electron donor that can promote the activity of bacteria that mediate reductive dechlorination reactions. The electron donors can be augmented with a bacterial culture or consortium with proven ability to fully degrade common chlorinated solvents. ISCR treatment combines an organic electron donor addition with a chemical reducing agent, such as zero valent iron (ZVI) or divalent iron (DVI). In general, ERD is seen as the simplest technical approach for many chlorinated solvent sites, while ISCR is viewed as a more robust technology capable of dealing with more challenging groundwater conditions (e.g., wide range of pH, high sulfate levels, persistent contaminant sources, combined organics and metals).
Objectives.
Several factors should be taken into account when selecting an organic electron donor for use in ERD or ISCR applications, including cost, ease of use, and longevity. A wide variety of carbon substrates, including lactate, molasses, and vegetable oil, have been used in ERD and ISCR applications in the past. Recently, lecithin has been identified as a potentially advantageous organic electron donor based on its physical, chemical, and nutritional properties. This work involved testing of lecithin alone, and lecithin supplemented with DVI, under bench-scale, pilot-scale, and full-scale conditions. The full-scale applications were conducted at military sites in Texas and California, USA.
Approach/Activities: Bench-scale studies determined the influence of lecithin, and lecithin supplemented with DVI, on groundwater ORP, pH, TOC, and TCE degradation, including production and destruction of daughter products. Pilot-scale demonstrations focused on delivery of the lecithin substrate to the subsurface and evaluation of its influence on TCE degradation. Full-scale applications involved treatment of a TCE plumes and included monitoring of recognized ERD parameters including target compound degradation, metabolite generation and removal, and cost analysis.
Conclusions.
Bench-scale studies indicated that both lecithin and lecithin supplemented with DVI generated reducing conditions more rapidly than alternative organic carbon substrates, and supported TCE removal for more than 15 months. The pilot-scale demonstration enabled estimation of the zone of influence and addressed the issues of large-scale emulsion preparation, dilution, and injection methodology. Full-scale application focused on scale-up issues of substrate preparation, delivery, injection, distribution, TCE and metabolite degradation, and impacts on aquifer geochemistry. Cost information will also be presented.
Keywords: ERD, ISCR, DVI, Lecithin, Bio-Chemical Treatment, Metabolite Degradation, Groundwater Remediation, Chlorinated Solvents
A recent release of approximately 7,600 Kilograms of trichloroethylene (TCE) that occurred in the mid-90s resulted in an 18-meter thick impacted vadose zone and a 6-hectare dissolved groundwater plume. Early testing conducted in 2001 and 2003 identified TCE concentrations in the source area as high as 81,000 mg/Kg in soil and 1,200 mg/L in groundwater, near its water solubility limit. The owner has set ambitious clean-up objectives to reach the allowable regulatory TCE concentration of 5 ug/L throughout the entire plume by the year 2025. Multiple interim and final remedial approaches were implemented toward achieving this goal. Traditional and innovative technologies were applied, two of which are not usually considered in consort for the same site. This presentation will discuss remediation performance following a full scale injection of In-Situ Chemical Oxidation (ISCO) and In-Situ Chemical Reduction (ISCR) reagents that were pilot tested at the site, the results of which were presented at this conference in 2013.
Meeting the site clean-up goal required an aggressive approach of intensive interim remedial measures while completing the Remedial Investigation, Risk Assessment, and Feasibility Study, followed by a comprehensive final Remedial Action. A remediation strategy was developed to meet the various technical and schedule requirements of this particularly challenging site characterized by relatively high source area concentrations, low permeability saprolite overlying fractured bedrock, low natural attenuation rate, large plume area with limited accessibility, and a very aggressive remediation timeframe.
Approximately 89% of the contaminant mass was removed by the interim remedies, which consisted of excavation, soil vapor extraction (SVE) and In-Situ Thermal Desorption (ISTD) in the source area, and a Pump & Treat system along the property boundary. In the final remedy, these were replaced by SVE in the vadose zone, aggressive ISCO injection for rapid and complete contaminant mass removal in the source area aquifer, and a series of passive, long-lasting permeable reactive barriers (PRBs) using ISCR to address long-term contaminant advection and diffusion in the plume area. The latter two technologies are rarely applied at the same site because of their antagonistic redox environment and must be given careful consideration during design and implementation. However, their application as parts of the same combined remedy can be greatly beneficial to challenging sites. The efficacy of combining the antagonistic ISCO/ISCR remedial approaches was pilot tested at the same site prior to the full scale implementation. Modeling and monitoring were conducted during design and implementation as a basis for reagent requirements, injection point spacing, scale-up for future expansion of the treatment, and to ensure reagents do not interact and destroy each other. The injection wells were installed using sonic drilling methods to allow for a close examination of the overburden and bedrock core in the target injection intervals. Due to the low-permeability saprolite and random fracturing patterns in bedrock, traditional injection methods have proven unsuccessful at this site. Hence, both reagents were emplaced as slurry using a hydraulic injection technique in the form of fractures at a 1.2-meter vertical spacing.
For the ISCO source area treatment, 75 metric tons of potassium permanganate (KMnO4) and sand blend (50% each) were injected in three stages between 2011 and 2014, including the pilot study. Seventeen injection wells were used covering an area of approximately 390 square meters and extending 24 meters into the saprolite overburden and 4 meters into the underlying fractured granitic gneiss. The ISCR treatment consisted of three zero-valent iron (ZVI) PRBs that effectively divide the plume into four segments, thereby drastically shortening its lifespan. A total of 658 metric tons of granular ZVI were injected into 62 injections wells with 6 meters of separation between wells and PRB lengths ranging from 73 meters to 161 meters. Vertically, the PRBs extended up to 26 meters into the saprolite and up to 13 meters into the underlying granitic schist and gneiss.
Performance monitoring has been conducted at least quarterly. As of the fourth quarter of 2014, approximately 80 Kgs of TCE have been removed from the vadose zone by the SVE system. A similar amount (~74 Kgs) has been removed by the ISCO injection. It is estimated the clean-up goal in the source area (<5.0 ug/L) should be met after the removal of an additional 2 Kgs. Of the 15 monitoring wells in the source area, 11 wells have experienced complete TCE concentration reduction (>99.99%). TCE concentrations in the remaining four wells dropped by 92% to 99.5% from the ISCO baseline levels. Permanganate was not observed in any of the wells located outside the source area, and reducing conditions have been sustained in the immediately downgradient ZVI injection wells; therefore, the permanganate did not adversely affect the PRBs.
The ZVI performance monitoring wells have exhibited significant reductions in TCE concentrations ranging between 90.5% and 99.8% at the most upgradient PRB, but at lower rates in the mid-PRB (69.7% - 100%) and most downgradient PRB (34% - 59%), where groundwater flow rates are relatively lower.
Dual-phase extraction (DPE) or pump-and-treat (P&T) systems are widely used for the remediation of high concentrations of hydrocarbon nonaqueous phase liquid (NAPL) at contaminated sites. While the initial phase of DPE system operation typically achieves rapid reduction of NAPL the long-term effectiveness diminishes and the system often reaches an asymptote. Further operation of a system in asymptote conditions would provide little incremental benefit in treating soil or groundwater contamination thus negatively impacting both project costs and time.
The leveling off of DPE effectiveness typically arises as a result of hydrocarbon distribution through zones of differential matrix permeability, the presence of slowly dissolving smeared or sorbed hydrocarbon contamination, or a combination of both of these factors. For many remediation practitioners the next logical choice for remediation when DPE operation is asymptotic is to use In Situ Chemical Oxidation (ISCO). While the use of ISCO can be successful in many instances there are still two main limitations to ISCO to treat heavy sorbed phase contamination. The first being that DPE systems are often used in low permeability sites where they achieve greater treatment radii because of the beneficial use of high vacuum flow. These very same soils may prevent efficient distribution and contact of a chemical oxidant. The second point is that while a DPE system may have reached an asymptote the corresponding soil and groundwater concentrations may still be quite high meaning that the number of injections and volume of reagent required would be costly.
The use of surfactants to enhance recovery of sorbed-phase or smeared hydrocarbon is another option, but applications are rare owing to perceptions of cost, pore-blockage, trapping of residual hydrocarbons by sub-CMC residual surfactant, and high residual surfactant biological oxygen demand (BOD) that inhibit follow-on biodegradation or natural / enhanced attenuation of residual hydrocarbon.
This presentation will provide information on a reagent-based approach which systematically addresses the above issues in order to increase the efficiency and expedite the closure of physical extraction-based clean-up projects (DPE, pump-and-treat, etc.). This technology is entirely inorganic and presents no BOD yet provides combined ISCO and enhanced desorption at contaminated sites to treat bound hydrocarbon and NAPL. This approach can also be used to increase efficiency at failing DPE installations for fast and cost-effective mass reduction. An overview of the results from laboratory and field studies will be presented and the potential modes of usage and anticipated benefits to common remediation projects explored.
Chlorinated solvents are one of the most abundant contaminants of groundwater due to its frequent historical industrial exploitation. Chlorinated solvents are accompanied very often by hexavalent chromium Cr(VI) as a result of improper handling these chemicals during degreasing and subsequent metal plating processes. Despite of approximately 25 years of remediation technology development, achieving typical concentration-based cleanup goals in soil and groundwater for these constituents remains technically challenging at many contaminated sites. This study combines in-situ chemical reduction by nanoscale zero-valent iron (nZVI) and subsequent biological reductive treatment, supported by addition of whey as an organic substrate in order to treat aquifer impacted by Cr(VI) and chlorinated ethenes. Added substrate as electron donor supports microbial reduction of Cr(VI) to non-toxic and significantly less mobile Cr(III), in addition, hydrogen and acetate as products of substrate fermentation serve as the electron donors in reductive dechlorination of chlorinated ethenes.
Combining these two remedial approaches takes advantage of features from both – fast nZVI-mediated decrease of Cr(VI) concentrations in source area groundwater to prevent the further spread of the contamination followed by more economical treatment of chlorinated ethenes and the lower Cr(VI) concentrations in the plume by microorganisms.
The combined technology was tested in the field at a pilot site where the initial Cr(VI) concentration in groundwater ranged from 4.4 to 57 mg/l. The total concentration of chlorinated ethenes ranged from 400 to 6526 µg/l. Trichloroethene (TCE) and cis-1,2-dichloroethene (cis-DCE) were dominant chlorinated contaminants (TCE formed 45% up to 93% and cis-DCE formed 5% up to 53% of total chlorinated ethenes on a molar basis). At the pilot test site the aquifer lies in Quaternary sands and gravels with a saturated thickness of 4 m. nZVI was injected twice with a 4-month interval. 20 kg of pure nZVI in suspension was used for each injection using a direct push technology. Two months after the second nZVI injection, whey was added in order to achieve 60 mg TOC/l in groundwater.
During the pilot test, the applications of nZVI rapidly pretreated the aquifer with regards to toxic Cr(VI) and to some extend also to chlorinated ethenes without any negative impact on the composition or abundance of indigenous bacteria. Stimulation of biological reductive treatment using whey resulted in a further decrease in Cr(VI) concentrations in the groundwater below a detection limit (<0.05 mg/l) throughout the treated areas without any rebound of Cr(VI) concentrations after substrate depletion. Addition of whey resulted in a temporal increase of concentration of chlorinated ethenes as a consequence of the desorption/solubilisation effect of whey and its metabolites in the groundwater followed by intensive subsequent dechlorination of chlorinated ethenes up to ethene and ethane.
The chlorine number (average number of Cl atoms per ethane in the groundwater sample from down-gradient monitoring wells) decreased from initial 2.6 – 2.8 to 0.1 – 0.9 approximately 3.5 months after addition of whey. Within the same time the total concentration of chlorinated ethenes decreased to the range from 69 to 747 µg/l (the pilot test is on-going).
The results of PLFA analyses clearly indicated positive effect of nZVI injection on the abundance of indigenous microorganisms. The effect of whey application was rather complex and will be evaluated in a paper in detail. Dechlorinating bacteria belonging to genus Dehalobacter, Dehalococcoides and Sulfurospirillium were detected by polymerase chain reaction (PCR) or quantitative PCR (qPCR) in groundwater during the test. Cultivation tests showed positive effect of both nZVI and whey injection on psychrophilic bacteria.
No adverse effects to hydrochemical composition of groundwater were observed. Depletion of nitrate, temporary elevated concentrations of iron and manganese and a decrease in the content of sulphate are (together with a drop of EH) common indicators of the created thermodynamically favorable conditions for reduction of both contaminants.
In sum, the successive combination of the two in-situ methods – chemical reduction by nZVI and biological reductive treatment seems to be an efficient and sustainable remedial approach for treatment of the mixture of the rather frequent contaminants - Cr(VI) and chlorinated ethenes.
Abstract
Many shallow lakes suffer from accumulation of fine sediment. This sediment build-up is caused by different factors like shoreline erosion, peat degradation, internal organic production and external inflow or run-off. Fine sediment is kept in suspension, thereby inhibiting growth of higher order aquatic plants and natural water quality improvement. In a protected wetland area innovative and sustainable measures have been undertaken to reduce hydrodynamics, sediment resuspension and turbidity in order to remediate contaminated sediment, enhance biodiversity and improve water quality.
Two types of light weight geotextile constructions were built to steer fines and to store sediment: the Sediment Settler and Sediment Storer. Due to the Sediment Settler fines transport decreased by 20-40 %. One year after installing the Sediment Settler a few decimeters thick sediment layer had already been formed at its lee side. Also about 15.000 cubic meters of slightly contaminated sediment was dredged and transported to
Sediment Stores in order to alter hydrodynamics and induce nature development. By doing so, maintenance costs were minimized and sediment had been beneficially re-used. By the end of the first growing season the sediment top layer was covered by a pioneer vegetation of reedmace. Even species that have disappeared 30 years ago returned.
Figure: Schematisation of Sediment Settler
This pilot study has shown that it is possible to control sediment settling and transport and improving recreational and ecological quality of this wetland area. Nautical bottlenecks were reduced and in lee areas
vegetation develops. So, synergies were realized between remediation, nature restoration and (at some locations) shore line protection. Dredged
material can easily be kept and stored in submerged basins.
Figure: Photograph of Sediment
Storer Keywords: Geotextile construction, sediment storage, fine transport, water quality, shoreline protection
In recent years, Israel is undergoing vast national infrastructure development. Such projects generate significant volumes of excavated soils. Unfortunately, huge piles of excavated soil in the vicinity of infrastructure works have become a common sight.
Such development imposes significant stress on resources conservation and calls for an intelligent management of such primary raw materials. Governmental reports indicate that in the near future, Israel is expected to face a crisis in supplies of mined and quarried materials. The expected extraction mining capacity is scarce, and statutory approval for new quarries is practically impossible to achieve. This situation is expected to lead to higher construction costs – a stressful economic issue in the Israeli reality.
Although previous policy documents have been written on the matter, and there is clear recognition regarding the existence of a problem, too little is done when it comes to large scale infrastructure projects.
The free markets do not willingly absorb the residual excavated soils and although better priced, and sometimes even given away for free at the excavation site. At present only negligible amounts of excavated materials are consumed indicating the clear preference for primary raw materials. The problem becomes more acute when polluted soils and Brownfields are the origin of the excavated soils. A major ball game changer is the excavation project of the first underground light-rail in the Tel-Aviv metropolitan area. This project will generate during the next 4 years, unique circumstances which necessitated the establishment of a Transit Hub Site (THS) solution. It is not only that 3 million cubic meters of soil will be excavated in the project but an environmental survey that was conducted along the excavation route indicated the potential contamination of up to 30% of the total volume of soils in addition to ground water contamination.
Therefore, sampling and characterization of excavated soils prior to their transportation to the final destination was mandated all together with confirming analysis at the hub site. The suggested receiving hub site is a metropolitan park under construction that was used in the past for open landfilling of Tel-Aviv municipal garbage. The surplus excavated soils will be beneficially used for the stabilization of the closed landfill slopes and for the creation of landscape hills. This solution will also create an economic benefit since no further transportation will be required. Contaminated soils will be mostly depolluted on the Hub site.
The complex challenge for the team was to obtain regulatory acceptance for the move, since no regulative reference was available in the current Israeli environmental policy. No other THS was ever operative in Israel in a similar manner that implements the full process of handling and treatment of large amount of clean soils of various textures mixed and the recycling of contaminated soils.
The concept of THS in which soil is sampled, treated or recycled and may be re-used for beneficial purposes, is innovative to Israel. The only permit for beneficial use up till now is as a cover layer in landfills for soils that were sampled for the threshold-value of less than 5000 ppm of TPH.
The presentation will describe the developed process for the absorption of surplus excavated soils from the excavation in the dense urban area till its final destination as a fill material in the park.
Background
In major urban areas, construction activities often generate large quantities of soil which are disposed of in ways that are not always beneficial to the environment. In the Copenhagen area, construction projects generate some 10 million tons of excavated soil each year. This soil is often transported to distant locations where disposal is cheap, causing excess transport emissions and potentially endangering land use or water-resources. Unfortunately, Danish regulation and market conditions do not encourage sustainable reuse of soil. In order to address this problem, the Capital Region of Denmark launched an initiative in 2013 to in-crease sustainable reuse of excavated soil.
Aim
The aim of the initiative is to increase resource efficiency by transforming excavated soil from waste-status into a sustainable resource, preferably used locally for a wide range of purposes.
Important goals for the Capital Region are increased reuse of soil in construction projects, reducing the demand for sand and gravel and also reducing emissions from road-transport.
The initiative has a three year time-frame and a budget of €1.2 million. A total of 9 individual projects are currently in progress. Each project is based on a partnership between public and private stakeholders, including contractors, developers, producers of bricks, lime and gravel, local counties, and consulting companies. The projects focus on f. inst. tools for planning and development, stabilization of clayey glacial till, sustainable use of topsoil (from large railroad projects) on arable land, a website for soil exchange, mitigation of climate change (flood control etc.) and in construction of energy plants (hydro-power and thermal storage). A selection of preliminary results will be presented at the conference.
Conclusion
The initiative of the Capital Region of Denmark demonstrates that innovative ideas and solutions can be found, when private and public stakeholders team-up. The formation of public-private sector partnerships has proved to be time consuming. The partnership-model however has also proved very inspiring and valuable for seeking new (and profitable) uses for excavated soil.
At present, new ideas are being developed and evaluated and the mind-set of the stakeholders is gradually changing as they realize that sustainable reuse makes sense and can in fact be profitable.
Biochar produced from a wide range of organic materials by pyrolysis has been widely reported as a means to improve soil physico-chemical properties, fertility and crop productivity moreover to mitigate climate change. However, the effects of biochar on soil ecosystem and microbial activity have received much less attention than its effects on soil physico-chemical properties.
The key objective of this research was to determine the effect of biochar amendment on physico-chemical properties of sandy acidic soil as well as on activity of soil biota. Laboratory microcosm experiments were conducted to improve soil quality combining variations in biochar amounts and fertilizer application rates (N and P).
The biochars applied were produced in a PYREG® type pyrolyser at temperatures between 450 and 700 °C during 15-20 min residence time from different feedstocks such as grain husks, paper fiber sludge, wood screenings, vine, black cherry, natural biomass, straw, olive stones and meadow.
The main purpose of soil technological microcosms was to assess efficiency and applicability of different biochars as soil amendments prior to field trials and to choose the best biochars that are able to improve the fertility, biological activity and physical propoerties of degraded soils particularly acidic sandy soil furthermore to determine the optimum technological parameters in microcosms.
To assess and evaluate the potential benefits and feasibility moreover risks of biochars on soil an integrated approach was applied including physical, chemical, biological and ecotoxicological methods: water holding capacity, pH, EC, elemental concentrations, nutrient supply, nitrification, soil respiration, CO2 production and specific cell concentrations as well as toxicity for bacteria (Aliivibrio fischeri), plants (Sinapis alba and Triticum aestivum) and animals (Tetrahymena pyriformis, Folsomia candida) were determined in soil microcosms.
Acknowledgement:
The work was carried out in the frame of the „Terra Preta” project, registration number HU09-0029-A1-2013 supported by the EEA Grants and the Norway Grants within the „Green Industry Innovation Program” of the Norwegian Financial Mechanism 2009-2014.
Soil was one of the seven thematic strategies that were to be addressed in the 6th EU Environment Action Plan (EAP) as an essentially non-renewable source due the time period over which soil is formed. The value of soil as a resource is many faceted, performing a number of vital functions including but limited to production, filtration and carbon storage. Moreover it provides a platform for human activity and yet it is such activity which has led to loss of this valuable resource from the impact and pressures of human activity.
Soil in construction historically has not been valued with loss due to sealing and landfilling of surplus soils whether contaminated or not. Whilst sealing may be in circumstances unavoidable landfilling often is not. Over the years, we’ve all witnessed material going to landfill that could be reused on another site, so what are the barriers to such intuitively cost effective and sustainable solutions. In line with the EU 7th EAP whose second action area concerns the conditions that will help transform the EU into a resource-efficient, low-carbon
economy AECOM has been seeking to promote greater resource efficiency and has firsthand experience of the challenges to soil reuse even in an economy where landfill tax has increased the drive for more sustainable solutions.
The frustration of our clients at the costs involved with importing and exporting soils and a TV advertisement for online dating provided the inspiration for our new soils management service called Waste Harmony®. Changes in legislation and guidance mean that the concept of a soils dating agency is now a genuine reality. The name was how we initially, somewhat jokingly, referred to the idea, but it has really captured people’s imaginations and so we’ve decided to build on the analogy. Where someone has surplus soil arisings, this needn’t be a waste, but rather can be a valuable asset for someone who is looking for that material. Using our client networks, it was clear that we could set up an exchange that provided a truly cost-effective and sustainable alternative management solution.
With huge potential across the industry, this innovative idea has been developed with support from AECOM’s Creative and Technical Excellence Council. This presentation will look at the challenges posed by what in essence is a simple concept but is more often than not implemented for a range of reasons and the in-house tools that we have developed to overcome some of these challenges including the financial model for understanding the economic viability of matches and, in keeping with the dating agency theme, an online portal. It will include a couple of case studies showing the scheme in action.
Background/Objectives. Success of large-scale in-situ remedies is often limited by a conceptual site model (CSM) and hydrostratigraphic understanding that is too general and does not allow for location-specific remedy optimization. Without a comprehensive and local understanding of the hydrostratigraphy, delivery of reagent may be inadequate in areas, resulting in incomplete treatment and longer treatment duration. Conventional performance data, typically collected at monitoring wells within the treatment zone, may not detect this incomplete treatment or may not provide adequate information to adapt the remedy to improve performance.
However, “next-generation” characterization tools and three-dimensional modeling can be costeffectively used to refine the CSM, identify zones of high contaminant flux, and optimize
remedy performance. Since 2001, an enhanced reductive dechlorination (ERD) remedy has been implemented to treat a 2,000-foot long trichloroethene (TCE) plume. The original remedial design was based on a pre-existing CSM that relied on conventional investigation methods such as visual borehole logging and groundwater sampling from site monitoring wells. Twodimensional analysis of available data did not capture the lateral continuity of higher transmissivity hydrostratigraphic units responsible for the bulk of solute transport. After four years of full-scale remediation, conditions favorable for ERD had been established in most areas of the site. However, incomplete remediation was observed in some locations of the plume.
Approach/Activities. To further develop the CSM and understand why treatment was not
observed in some areas of the site, traditional performance monitoring data was supplemented with four targeted investigations using multiple “next generation” high resolution characterization techniques including cone penetrometer (CPT), hydraulic profiling tool (HPT), and membrane interface probe (MIP). Historical and the more recent high-resolution data were integrated into a three-dimensional model using Environmental Visualization System (EVS) software to gain an improved understanding of the hydrostratigraphy and contaminant migration pathways, and this new understand provided a basis for modifications to remedy design and implementation.
Results/Lessons Learned. Three-dimensional modeling and visualization of the indicated lateral continuity of hydrostratigraphic units previously thought to be disconnected providing a refined CSM that was used to significantly expand and optimize the current remedial system. Remedy changes included the installation of additional injection wells, abandonment of select injection wells deemed no longer necessary for operation and monitoring, and adjustment of reagent injection volumes. After adjusting remedial operations, improvements in performance were observed within months. This case study highlights how these new tools and approaches can be effectively used to address the challenges of full-scale plume treatment and maximize effectiveness of in situ approaches.
The public water management of Lower Saxony has to provide about 8 million people with fresh water. With a portion of 71% of the public water supply in Germany (BGR 2010), the fresh groundwater is the most important resource for urban, agricultural and industrial activities. Some of the aquifers used for groundwater extraction provide problems with intruding salt water from different sources (GRUBE et al. 2000). Especially the coastal aquifers may be vulnerable for sea water intrusion, which is the landward encroachment of sea water into fresh water aquifers (IVKOVIC et al. 2012). This process could be enhanced or initiated by anthropogenic activities. Because of the importance of the salt water intrusion problems, the State Authority for Mining, Energy and Geology (LBEG) planed, based on a pilot project in the area of Esens (DEUS 2012), to generate a statewide “salt water map” for Lower Saxony with a focus on the coastal aquifers influenced by sea water intrusion.
In Germany the use of fresh water as drinking water is limited through the thresholds for different parameters in the “Trinkwasserverordnung (German drinking water regulation)” (BMJ 2013). Those are 250 mg/l chloride, 250 mg/l sulfate and 200 mg/l sodium (BMJ 2013). The threshold for the electrical conductivity at 20°C is 2790 µS/cm (BMJ 2013) which correlates with an electric resistivity of 4 Ωm. These parameters were used to characterize the groundwater and divide it into salt-/fresh water areas.
For the coastal regions of Lower Saxony we use airborne electromagnetic measurements (HEM) operated by the “Federal Institute for Geosciences and Natural Resources (BGR)” to get the electric resistivity of the underground (sediments and pore fluids) and combined them with groundwater analyses to detect the intrusion of sea water into the aquifers. Therefore, referring to the experiences and results of DEUS (2012), we combined the resistivity distribution with geological 3D-model of the Pleistocene sediments, containing information from geological maps, profiles, wells and groundwater analyses to distinguish low resistivity’s caused by sea water intrusion, from those caused by clay materials which have the same resistivity. The resistivity data from the electromagnetic measurements were integrated in GOCAD® and the area affected by sea water intrusion was visualized as a 3D surface, which represents the salt-/freshwater interface.
BGR (2010): Grundwasseranteil an der öffentlichen Was¬serversorgung der Bundesländer in 2007. http://www. bgr.bund.de/nn_322854/DE/Themen/Wasser/grund¬wasser__gewin__tab.html, Abruf 01.12.2010.
DEUS, N. (2012): Kartierung der Küstenversalzung mit Hilfe geophysikalischer Daten und 3D-Modellierung im Raum Esens (Ostfriesland). Hannover (unveröff. Masterarbeit Univ. Hannover), 92pp.
GRUBE, A, WICHMANN, K., HAHN, L. & NACHTIGALL, K.H. (2000): Geogene Grundwasserversalzung in den Poren-Grundwasserleitern Norddeutschlands und ihre Bedeutung für die Wasserwirtschaft. TZW-Schrift¬enreihe, 9, Karlsruhe, 203 pp.
IVKOVIC, K.M., MARSHALL, S.K., MORGAN, L.K., WERNER, A.D., CAREY, H., COOK, S., SUNDARAM, B., NORMAN, R., WALLACE, L., CARUANA, L., DIXON-JAIN, P. & SIMON, D. (2012): National-scale vulnerability assessment of seawater intrusion: summary report. Waterlines Report Series No 85, Australia, 185 pp.
BMJ (BUNDESMINISTERIUM FÜR JUSTIZ) (2013): Trinkwasserverordnung in der Fassung der Bekanntmachung vom 2. August 2013 (BGBl. I S. 2977), die durch Artikel 4 Absatz 22 des Gesetzes vom 7. August 2013 (BGBl. I S. 3154) geändert worden ist. – Berlin.
Background and objective
The understanding of chlorinated solvents behavior in fractured limestone aquifers is a challenging task because of the preferential flow of contaminants in fractures and the exchange with the limestone matrix. Characterization of the contaminant distribution, particularly in the matrix, is challenged by difficulties in intact sample collection (coring) for sufficiently discretized data. The characterization is important for the development of a conceptual understanding, for risk assessment and for the choice and operation of an appropriate remediation strategy. The FACT (FLUTe activated carbon technique) is an innovative monitoring technique, which allows determining the distribution of a contaminant in the surrounding of a borehole with a higher resolution than conventional monitoring methods. The FACT technique proved to be a helpful tool for characterization of contaminant distribution in the limestone aquifer at Naverland, a contaminanted site in Denmark (Janniche et al. 2013, Broholm et al. 2013, Kerrn-Jespersen et al. 2013). While the sorbed concentration of contaminant in the carbon felt is obviously related to concentrations in the formation, there is no direct relation between measured sorbed concentration (mg/g AC) and the aqueous pore water concentration (mg/L). The objective of the research presented was to develop a tool for the interpretation of FACT measurements and apply it to the Naverland dataset for comparison with concentrations in groundwater samples sampled from the Water-FLUTe multilevels (Janniche et al. 2013 and 2013b) at the site.
Method and technique
The FLUTe Activated Carbon Technique was described e.g. in Janniche et al. (2013). The sorption of chlorinated ethenes on activated carbon was determined in laboratory experiments as described in Sørensen et al. (2014) to obtain equilibrium sorption coefficients (Kd) for individual and mixed chlorinated ethenes on activated carbon from aqueous solution. As the uptake on FACT in limestone aquifers will depend on transport (advection and/or diffusion and retardation by sorption) in the limestone matrix and fractures as well as on the sorption to activated carbon, a modeling tool was developed (Mosthaf et al. 2014) which allows for the interpretation of field data and the analysis of the influence of various aquifer parameters. The model provides a link between sorbed concentrations on the FACT and the prevailing aqueous pore water concentrations for a range of hydraulic parameters and conditions typical for limestone aquifers.
Results and outlook
The sorption experiments showed very strong sorption with reasonably linear sorption isotherms over a very large concentration range for individual chlorinated ethenes. At high PCE concentrations, competition for sorption sites resulted in non-linearity and much lower sorption of the less hydrophobic compounds TCE and particularly c-DCE. The model simulation results demonstrate the influence of common aquifer parameters on the observed sorbed concentrations on the FACT. The influence of the porosity and of the positioning of the FACT with respect to the flow is comparably small (factor 2-3), whereas the influence of sorption coefficients is increasing with the sorption coefficients and is particularly important for Kd-values above 10-3 L/kg. The hydraulic conductivity has only little influence for values below 10-5 m/s, but up to orders of magnitude influence above that until diffusion within the FACT is limiting the transport processes. For given hydraulic parameters, conditions and exposure time of the FACT, a linear relation between activated carbon concentration and aqueous concentration can be established. This allows the FACT-FLUTe technology to be employed for the characterization of contaminant distribution in limestone aquifers. A comparison between the aqueous (pore water) concentrations calculated with the model from the FACT-FLUTE data with groundwater concentrations from the Water-FLUTe multilevels at the Naverland site showed good correspondence. An advantage of the FACT technique is that it provides discretized data for the matrix and is less influenced by the preferential flow in high conductive zones than multilevel water sampling. It can also be applied in a matrix with strong variation in the hardness (e.g. softer limestone with interbedded chert layers). Furthermore, DNAPL presence in hydraulically active fractures can potentially be identified by high concentration peaks on the FACT.
Literature
Broholm, M.M. et al., 2013. Udvikling af konceptuel forståelse af DNAPL udbredelse i moræneler og kalk ved integreret anvendelse af direkte og indirekte karakteriseringsmetoder. ATV Vintermøde, Vingsted, 5-6. marts 2013.
Janniche, G.S., Fjordbøge, A.S., Broholm, M.M., 2013. ”DNAPL i moræneler og kalk. Vurdering af undersøgelsesmetoder og konceptuel modeludvikling. Naverland 26AB, Albertslund.” DTU Miljø og Region Hovedstaden. www.sara.env.dtu.dk.
Janniche, G.S. et al., 2013b. ”Anvendelse af Water FLUTe multi-level vandprøvetagning til DNAPL karakterisering.” Jordforurening.info 2-13, p. 4-8. Videncenter for Jordforurening. www.jordforurening.info
Kerrn-Jespersen et al., 2013. ”Undersøgelsesmetoder til karakterisering af DNAPL i kalk.” Jordforurening.info 1-13, p. 20-23. Videncenter for Jordforurening. www.jordforurening.info
Mosthaf, K., Broholm, M.M., Binning, P., 2014. ”The FACT-FLUTe technology. A modeling tool for interpreting field data.” DTU Environment and Region Hovedstaden. To appear on www.sara.env.dtu.dk
Sørensen, M.B., Broholm, M.M., 2014. ”Sorption af chlorerede opløsningsmidler på FACT.” DTU Miljø and Region Hovedstaden. www.sara.env.dtu.dk.
The old city centre of Delft is sensitive to both pluvial and fluvial flooding, especially specific areas in the eastern part of the city centre. This includes high groundwater levels, overflowing of canals, surcharging of sewers and flooding of streets and buildings due to storm events. In order to reduce flooding impacts, the canals in the city centre have been separated from the main water system around Delft by means of several weirs which can be closed when heavy rainfall is expected. The city centre also contains several soil contaminated sites, which are most probably influenced by the control of the other parts of the water system in the city (sewer, groundwater and surface water). From 2011 till 2015 a research project was carried out to implement smart monitoring. Goal of the project is to improve water and soil management by creating useful information out of the monitoring data, that can be used for decision making for organizations, policy makers and society.
To study the behaviour of the water system and the interactions between the separate parts of this system, including sewer, groundwater, surface water and soil contamination, a monitoring network was installed. The network consists of online sensors to monitor changes of parameters in, and related to, the water system, such as water level, rainfall conductivity, temperature, turbidity, oxygen and redox potential. A location within the city centre that is contaminated with Chlorinated Volatile Organic Compound (VOC) is investigated in more detail. For this site, the sensor network provides real time information on a number of proxies. Additional monitoring rounds were carried out with electrode measurements and groundwater samples were taken for analyses on VOC and additional parameters (nitrate, methane a.o).
However, just measurements do not provide a prediction of the behaviour of the water system including a soil contamination. Therefore, high quality monitoring data and model results were integrated to information covering the complete water system of the city centre. In order to ensure high data quality, automatic validation algorithms were used which account for missing data, outliers, (linear) trends, signal variance and spatial correlations. A site model was developed for the contaminated site with the monitoring data that describes the spatial distribution of the contaminants and the degradation and transportation over time. The information of the complete water system of the city centre, including the detailed model of the contaminated site, is used to improve soil- and water management for the city centre of Delft.
The proposed paper (and presentation) presents the background of the monitoring system, the design and installation, the data acquisition, the development of the site model, the project results and advise for improved soil and water management in city centres.
Ethyl tert-butyl ether (ETBE), used as a fuel additive in motor gasoline to raise the octane number, is a frequently detected contaminant in soil and groundwater. When ETBE is accidentally released into the subsurface, it rapidly disperses in the environment due to its high water solubility and low interaction with organic matter. The low odor and flavor thresholds in water of 1-2 µg ETBE L-1 makes drinking water resources easily unpalatable. Applying Monitored Natural Attenuation (MNA) as a viable strategy to manage ETBE-contaminated sites bases on a comprehensive understanding of the site-specific biodegradation processes. In general, biodegradation of ETBE has been demonstrated by few microorganisms. However, the role of biodegradation in in situ reduction of ETBE contaminant loads has only scarcely been investigated.
In the present study, we investigated the in situ biodegradation of ETBE in a fuel-contaminated aquifer using two stable isotope tools: i) compound-specific stable isotope analysis (CSIA) and ii) in situ microcosms in combination with total lipid fatty acid (TLFA)-stable isotope probing (SIP). CSIA is based on the principle that molecules with heavier isotopes in their reactive position(s) (e.g., 13C, 2H) are generally slower degraded than those with lighter isotopes (e.g., 12C, 1H). The result is a shift in the isotopic composition (e.g., 13C/12C, 2H/1H) as the remaining contaminant fractions becomes progressively enriched in heavier isotopes (e.g., 13C, 2H) in the course of biodegradation. CSIA provides an appropriate tool to assess in situ degradation of individual environmental contaminants both qualitatively and quantitatively in contaminated aquifers [1, 2]. At the field site investigated, CSIA revealed insignificant 13C-enrichment but low 2H-enrichments with isotopic shifts up to +14 ‰ for ETBE, suggesting biodegradation of ETBE along the prevailing anoxic contaminant plume.
Ten months later, oxygen injection was conducted to enhance the biodegradation of petroleum hydrocarbons (PH) at the field site. Within the framework of this remediation measure, in situ microcosms loaded with 13C-labelled ETBE (BACTRAP®s) were exposed for 119 days in selected groundwater wells to assess the biodegradation of ETBE by TLFA-SIP under the following conditions: (i) ETBE as main contaminant; (ii) ETBE as main contaminant subjected to oxygen injection; (iii) ETBE plus other petroleum hydrocarbons (PH); (iv) ETBE plus other PH subjected to oxygen injection. In situ microcosms in combination 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 [3]). Under all conditions investigated, transformation of the 13C-carbon, derived from the 13C-labelled ETBE, into fatty acids was found, providing clear evidence of ETBE biodegradation at the field site. Based on the hydrochemical analysis, aerobic and anaerobic degradation of ETBE could be expected at the field site.
References:
1. R.U. Meckenstock, B. Morasch, C. Griebler, H.H. Richnow, Stable isotope fractionation analysis as a tool to monitor biodegradation in contaminated aquifers, J. Contam. Hydrol., 75 (2004) 215-255.
2. M. Thullner, F. Centler, H.H. Richnow, A. Fischer, Quantification of organic pollutant degradation in contaminated aquifers using compound specific stable isotope analysis - review of recent developments, Org. Geochem., 42 (2012) 1440-1460.
3. P. Bombach, H.H. Richnow, M. Kästner, A. Fischer, Current approaches for the assessment of in situ biodegradation, Appl Microbiol Biotechnol, 86 (2010) 839-852.
This session focuses on how to make decisions regarding the remedial strategy for contaminated sites and associated information requirements above and beyond the assessment data required to implement a management or active remediation strategy. Australia has been developing national guidance on the remediation of contaminated sites; this involves consideration of how other countries approach the problem, and how concepts such as risk-based land management and sustainable remediation should be included.
The concepts presented in this session should be of interest to many countries, particularly those that are grappling with how to achieve the greatest return from the investment in remediation of contaminated sites.
The session includes speakers who are highly experienced in remediating contaminated sites and have a good understanding of international approaches being applied, and the thinking that underlies good decision making related to contaminated sites. Papers will be provided on:
• Keynote address Presenter to be advised: Setting the scene: commentary on the international approaches and new developments in remediation strategy.
• Dr Peter Nadebaum (CRC CARE, ALGA, GHD, SuRF ANZ): Identifying the most appropriate remediation strategy: An outline of a structured approach to assessing the problem and deciding what strategy should be adopted, including taking into account regulatory requirements and necessary endpoints, the risk perception of the various stakeholders, the town planning interface and development options, the concepts of risk-based land management, the role of institutional controls, how to facilitate development when multiple sites are involved and the role of an auditor, the concepts of sustainable remediation, and how to achieve closure and an end to the remediation process.
• Dr John Hunt and Mr Ian Brookman (ALGA, Thiess Services, SuRF ANZ): Designing a remediation system – your Solution is only as good as the Problem definition: defining the remediation problem and the necessary endpoints, a contractor’s perspective and data requirements, interpreting assessment data, evaluating remediation options, data requirements above and beyond data gathered in the contaminated site assessment phase, maximising the value of assessment using standard interpretation techniques and the potential of further field investigation and treatability studies to reduce outcome risk and uncertainty , the maturity and certainty of the technology, and how to evaluate the sustainability of various options and how this might affect the technology selection.
• Mr Ian Brookman and Dr John Hunt (ALGA, Thiess Services, SuRF ANZ): Managing risk and uncertainty when Implementing a remediation system: the contractor and land developer’s perspective and requirements, how to define risk and how risks and potential liabilities should be shared between the various stakeholders, how to understand and allow for uncertainty, and how to address the problem if the technology doesn’t work to the level expected and contracted.
• A further external presentation chosen from the submitted abstracts and / or a facilitated discussion.
abstract #4949 is the second for the proposed session
We have been in contact with Dominique Demendrial and Hans Slanders and understand that the special sessions may have been oversubscribed with several around the Sustainable Remediation theme. So we propose an alternative session on site assessment and remediation, titled CONTAMINATED SITE REMEDIATION – A REAL WORLD APPROACH. While it has some apparent similarities with other sessions which we understand are proposed and are being considered by the technical program committee, we believe the proposed session has important differences. It draws on a vigorous debate that is occurring in Australia – referring to the various approaches existing and being proposed internationally. In particular, the proposed session considers how one should move from site assessment to remediation, how decision making really occurs, and the gaps in information that exist in many cases (that are often not apparent to the specialists skilled in assessment, but which are important to the contractors who have to decide on and design the remediation system). While we encourage applying the concepts of Sustainable Remediation (which we understand may be the subject of another session), we believe it is only part of the picture and actual decision making is based on much more. This is the message of the proposed alternative session, and we would propose to outline the issues and provide a suggested approach:
• CONTAMINATED SITE REMEDIATION – A REAL WORLD APPROACH
• Keynote – Peter Nadebaum – on the need to improve the process of moving from assessment to remediation, remediation selection and design requires more than what assessment requires, review of international and Australian perspectives.
• Presentation 1 John Hunt – on defining the problem
• Presentation 2 Ian Brookman - on managing remediation risks
• Presentation 3 – Facilitated discussion
In the early days of soil remediation, the first reaction was to strive for full removal of contaminated soil. Since then much has changed, and soil policies all over the world have evolved. While this evolution has varied depending on the economic climate and political setting, in general the following stages of evolution can be recognised: Growing Awareness of the Problem – Complete Removal – Risk Based Land Management – Risk Informed and Sustainable Remediation (SURF-US/NICOLE/Common Forum). Some countries have since proceeded further, considering sustainable management and use of the subsurface, which is an extension to the concept of sustainable use of land at the earth’s surface. Within this broad process of evolution, approaches and decision making can differ, and making decisions at a project level can vary markedly from the national policy framework. This paper provides an overview of innovative remediation solutions that are being adopted, and how decisions can be made to determine what is the most practical and appropriate solution for a contaminated site.
“Risk Informed and Sustainable Remediation”
Since the CLARINET report of 2002 many countries are moving to “Sustainable Remediation” of soil, sediment and groundwater, seeking to maximise the overall benefit through a balanced, evidence-based and transparent decision-making process, taking into account environmental, social and economic benefits and impacts of remedial strategies and options. This implies widening the scope of decision making, recognising that stakeholder involvement is crucial in minimising project-specific uncertainties, and allowing stakeholders to provide their perspectives on the balance of benefits and impacts. As a general decision framework “sustainability” is of great importance, and the first part of this paper will provide a short overview around the globe as to what is developing.
Moving on to innovative approaches, there are two aspects: new technical strategies, concepts and methods for dealing with the contamination; and new ways of evaluating options and making decisions.
New concepts and strategies, including consideration of the use of the subsurface
In densely populated Netherlands (and increasingly in neighbouring countries), the scale and number of contaminated sites is well known and there is growing awareness that other solutions are needed to tackle areas where the contamination is common and widespread. The process of reaching an agreement with all stakeholders (site owners, municipalities, water boards etc.) is well documented and examples will be presented of strategies involving for example “biowashing machines in city centres”, and remedial plans for areas of 200 km2. Groundwater extraction or Aquifer Thermal Energy systems are no longer prohibited, and are now encouraged because they can have a beneficial effect on the contaminants. Green remediation strategies involving solar or wind power are also being adopted. The biggest gain, however, will often be achieved by agreeing on reasonable and flexible remediation targets and levels. But the question is: how do we do this?
Decision tools
There are many frameworks and guidelines for assessing and remediating contaminated sites. Nearly every country has its own methodology. Many tools are available for evaluating or comparing remediation options; these include for example sustainability tools, and CO2 calculators. Multi-criteria analyses are widely practised; these can seek to balance benefits and impacts, but making indicators measurable and comparable and giving due consideration to essential matters such as effectiveness of a technology and likely outcome is often a challenge. How does the global soil community perform? We present an example that illustrates the issues.
End Point strategies
More and more we come to realize that every remediation project and site must come to an end, and that there should be a focus on minimising after care and reducing the risk that additional remediation will be required at some time in the future. Realising this leads to other decisions, more robust solutions and perhaps initial higher investments, or further consideration of remedial targets, within the context of a sustainable approach. This strategy is illustrated with a real life case in Amersfoort. This involved renegotiation of the clean-up strategy and the replacing a bioscreen (that would need continuous operation) with a physical, vertical narrowing of a funnel.
Total cost of Ownership
Selecting the remediation strategy also involves balancing the investigation/preparation cost against the resulting remediation cost. Often investing more in the investigation phase can result in a reduced cost of remediation, and vice versa.
This presentation is part of a free session proposal titled: CONTAMINATED SITE REMEDIATION – PRACTICAL DECISION MAKING
Determining the most appropriate remediation strategy for a contaminated site is often the single most important issue that a site owner or regulator has to resolve. Regulatory agencies have particular objectives; these are generally framed in terms of reducing the concentration of contaminants to below certain threshold values, and in some jurisdictions the practicability of achieving this outcome is taken into account. There is also increasing consideration being given to the principles of sustainability, with the objective not only being fixed on protection of human health and the environment, but also considering the benefits and trade-offs with respect to environmental, social and economic factors.
Formulation of a National Remediation Framework is underway in Australia to guide the industry on how to determine the most appropriate remediation strategy. This work is being led by Australia’s peak ?assessment and remediation research centre CRC CARE. Formulating a Remediation Framework has prompted thinking about the decision process that should apply.
The author is involved in this work and is contributing to the preparation of various modules that will make up the Framework, and is working closely with various organisations including government, industry, the Australasian Land and Groundwater Association, SuRF ANZ, and CRC CARE. This paper presents a personal view on the issues that arise in developing guidance on determining the most appropriate remediation strategy, reflecting various of the views that are being canvassed. A structured approach to the problem is suggested, taking into account regulatory requirements and necessary endpoints, the risk perception of the various stakeholders, the town planning interface and development options, the concepts of risk-based land management, the role of institutional controls, how to facilitate development when multiple sites are involved, the role of independent review and certification, when and how to take into account the principles of sustainable remediation, and how to achieve closure and an end to the remediation process.
The approach outlined seeks to protect key environmental values, encourage a wise use of resources commensurate with the problem, consider the views of stakeholders, have a measure of what constitutes “serious” contamination and requires careful management, and how to facilitate the development of brownfields comprising many individual contaminated sites.
As remediation contractors we too often are presented with remediation tenders where the remediation problem is poorly defined, the remediation solution is poorly thought through and the associated level of technical and commercial risk and uncertainty is unacceptably high. This presentation will discuss how to get the most out of the assessment data when defining a remediation problem with reference to ex-situ and insitu solutions, selection of an appropriate remediation solution and additional information requirements minimise risk when implementing the solution.
Many clients are unaware that once a problem has been identified that requires active remediation; the assessment data are insufficient to define the problem and remediation solution with certainty to manage technical and commercial risks during remediation. The outcome is that many remediation projects run over time and over budget resulting in costly commercial litigation. The key to implementing a cost effective and timely remediation solution is to adequately define the remediation problem by interpreting the remediation data and collecting additional information required to support a remediation solution.
All remediation problems require information on the:
• The extent and composition of the contaminated matrix to be treated including principally soil and groundwater. For soil this should include maps showing the thickness and structure of the affected strata particularly fill and bedrock, and estimates of composition including waste, oversize, grainsize, moisture content and density
• The nature of the contaminants including the concentration and mass distributions of the contaminants of concern, other contaminants, species or properties relevant to the potential remediation methods such as total organic carbon, material with calorific value and alkalinity / acidity;;
• Solution specific treatability data such as oxidant demand for oxidation methods, biological activity, nutrient status and inhibitors for bioremediation methods, leachability and compressive strength for stabilisation / immobilisation methods and calorific value and sulphur, fluorine, chlorine and nitrogen balances for thermal methods.
The above points will be illustrated with examples from real life showing the importance of using common methods to interpret assessment data and the role of treatability data in assessing technical risk.
Session 1b: Risk assessment and management (sub theme: Indoor air pollution from soil and groundwater)
Since the mid 90's vapor intrusion has been a major issue in Denmark and today vapor intrusion is a significant part of the efforts to ensure against contaminated sites. Investigation techniques and approaches to locate and determine the amount of vapor intrusion has been developed over the last two decades. This has given us a knowledge and understanding of the mechanisms controlling the vapor intrusion, which are amongst the best in the world. Remediation techniques have been developed and refined to provide greater security against vapor intrusion due to this knowledge.
The aim of the session is to share our knowledge about vapor intrusion including investigation and remediation techniques. Consideration of vapor intrusion vary from country to country due to political and cultural differences. However, differences in the ways vapor intrusion is handled, is also caused by differences in building constructions and climate. Factors that have great importance for processes that controls vapor intrusion. Another aim of the session is therefore to debate this diversity, in order to give both participants and speakers a better understanding of the similarities and differences and the extent to which we can apply knowledge and methods from one country / region to another.
We therefore propose that the open session will consist of both presentations and discussions with the following content:
• Methods for detecting vapor intrusions points, and vapor migration pathways in houses, including different measurements techniques for VOC's, tracer gases, thermography.
• Knowledge of vapor intrusion part ways, including traditional part ways as cracks in the concrete slap, pipe and wire penetrations of the slap, but also sewers, cavity walls etc.
• Different remediation techniques:
o Remediation techniques using passive venting systems. A technique with high sustainability and low operation cost, but do they work?
o Remediation using Hybrid venting system based upon solar and wind power
o Remediation using Geo-membranes
• Monitoring is an important part of the remediation process, both to ensure that desired barrier is obtained but also to develop and refine the remediation techniques.
• Lessons learned.
o We will strive to ensure that all presentations, in addition to providing an academically description of the methods developed, also include also include the topic "lessons learned".
o A short presentation to initiate a discussion on the similarities and differences between countries / regions.
Names of presenters and titles of presentations
• DMR, Per Loll. State of the art studies of vapor intrusions and migration pathways. The presentation includes different measurements techniques, and how to combine the results in risk assessment.
• Orbicon, Thomas H. Larsen. Remediation techniques using passive venting systems.
Passive venting systems are the most frequently used remediation technique against vapor intrusion due to its sustainability, high reliability and low operation cost. There are a variety of passive venting systems, each with their advantages and disadvantages. We present a case study describing the different passive venting systems.
• COWI, Tage V. Bote. Monitoring strategy.
Monitoring sounds like a simple exercise, but to implement a useful monitoring requires careful planning. Monitoring strategy has to be involved already in the design phase of the remediation, and it must fit into the plans for the construction of the building. This is to ensure that any errors or defects in remediation can be rectified as soon as possible in the building process. We present a case study describing the implementation process of the monitoring strategy.
• Orbicon, Bjarke N. Hoffmark. Remediation using Hybrid venting system based upon solar and wind power. The presentation describes a case study where the traditional passive ventilating system is improved but has preserved sustainability, high reliability and low operation cost. One of the disadvantage of passive venting system is that the driven forces is limited by very little pressure differences. Using the hybrid venting system the driven forces is significantly improved.
• The capital region, Arne Rokkjaer. Remediation using Geo-membranes or other remediation techniques. The capital region of Copenhagen is the largest actor in Denmark with respect to initiate actions to reduce or prevent vapor intrusion. As a regional authority they provide guidelines and setting conditions for the building permissions on contaminated sites, but they also finance remediation actions of existing housing. The presentation describes state of the art remediation actions.
• DMR, Per Loll. Lessons learned.
A short presentation to initiate a discussion on the similarities and differences between countries / regions.
Moderators: Per Loll, DMR, Bjarke N. Hoffmar, Orbicon & Tage Vikjær Bote * COWI.
*contactperson: Parallelvej 2, 2800 Lyngby, tvb@cowi.dk.
In the last decades, in situ chemical oxidation (ISCO) has become one of the attractive remedial alternatives for treating many organic contaminants. This remediation technique involves injecting oxidants (such as hydrogen peroxide, potassium permanganate or sodium persulfate) into the subsurface to destroy the compounds of concern. Many studies so far have demonstrated the effectiveness of the ISCO processes in the contaminated site remediation. Among the available oxidation processes the Fenton’s one gained an increasing interest due to its ability of treating a wide range of contaminants. However, the persistence of hydrogen peroxide in the subsurface is a key factor to consider since it affects the contact time of the oxidant with the contaminant and ultimately the delivery of H2O2 in the subsurface. With respect to other oxidants, such as potassium permanganate or persulfate, hydrogen peroxide in fact persists in soil and aquifer for relatively short times (from minutes to hours) and hence the radius of influence of the treatment could be relatively limited. To overcome this limitation, various reagents that enhance the lifetime of H2O2 in the aquifer can be used. Namely, the most common H2O2 stabilizers involves various forms of phosphate which reduce the availability of inorganic reactants (e.g. Fe and Mn) via complexation or precipitation reactions. More recently, different studies analysed the performances achievable using also organic acids, such as phytate, citrate and malonate. In this study we evaluate the performance achievable applying a Fenton-like treatment combined with carbon dioxide sparging. The applied CO2 stream in fact could in principle exert a double effect. On the one hand fluxing CO2 in water leads to carbonic acid production with a consequent decrease of pH to acidic values that makes the Fenton’s process more effective. On the other hand the CO2 sparging can enhance the contaminant removal due to a stripping effect. Thus to evaluate the performance of this combined process different lab-scale tests on a soil-water system artificially contaminated by MtBE were performed. In particular a Fenton-like process based on the use of hydrogen peroxide catalyzed by naturally occurring iron and manganese minerals was used. The oxidation process was then applied using either CO2 or KH2PO4 as stabilizing agents and the results, in terms of hydrogen peroxide lifetime and MtBE oxidation, were compared with the ones obtained without the addition of any hydrogen peroxide stabiliser. Furthermore, control tests applying only a carbon dioxide sparging without H2O2 were performed in order to evaluate the stripping effect of CO2. The obtained results showed that the use of either CO2 or KH2PO4 allows to enhance the hydrogen peroxide lifetime. However the stabilizing effect on hydrogen peroxide exerted by carbon dioxide was lower than the one observed when KH2PO4 was used. On the contrary, the removal of MtBE observed at the end of the different tests revealed that the combination of the Fenton-like process with the CO2 sparging was the most effective leading to a reduction of MtBE up to 99%. The application of CO2 sparging alone, instead, led to a MtBE removal in the order of 50-60% whereas the traditional Fenton-like with KH2PO4 allowed to remove up to 80-90% of the initial contaminant concentration. These findings hence suggest that the combination of carbon dioxide sparging with a Fenton-like process could represent a promising remediation option for the treatment of many organic compounds in groundwater.
INTRODUCTION
Polycyclic aromatic hydrocarbons (PAH) are organic compounds consisting of three or more fused benzene rings. PAH have low vapor pressure and negligible solubility in water. Due to their known toxicity, carcinogenic and mutagenic potentials, and their persistence in the environment, it is considered an international priority to take immediate, low cost measures for the removal of this kind of pollutants.
PAHs usually come from the incomplete combustion of organic matter, therefore these pollutants are usually found in coal and oil, coal tar, creosote, industrial areas, even in some cases of burnt food.
Advanced Oxidation Processes (AOPs) have shown good effectiveness in the removal of these contaminants, among all AOPs used for the remediation of PAH contaminated soils, it has become of increasing interest the use of activated persulfate, with a high redox potential of 2.12 V. Furthermore, stability of persulfate in soil is high, which can show activeness for months, making this reagent able to oxidize a wide range of organic contaminants. Besides, unlike hydrogen peroxide, non-productive consumption of persulfate is not strongly influenced by pH. [2], [3].
In spite of these advantages, there is a drawback regarding persulfate activation, which is related to the consumption of activator, as for example, iron. Taking into account that Fe(II) is the specie that activates persulfate for the release of persulfate radicals, when all Fe(II) is oxidized to Fe(III) during activation the release of persulfate radicals is stopped. This can be solved by different ways, as for example by the use of zerovalent iron, which acts as a continuous dose of iron, or the addition of humic acids, which can reduce Fe(III) to Fe(II), increasing the extent of the remediation technique.
The scope of this work is to remediate a PAH contaminated soil by 4 PAHs (anthracene, phenanthrene, pyrene and benzo(a)pyrene) by different kinds of persulfate activation, such as the addition of zerovalent iron (ZVI), either granular or nanoparticle, the addition of ferric sulfate combined with humic acids and the addition of surfactant, in order to increase the pollutant’s solubility. The different species involved in the reaction have been monitored (contaminant, oxidant) and also pH.
EXPERIMENTAL
A sandy loam soil was spiked artificially with 100 mg•kg-1each of 4 PAH, Anthracene (3 rings), Phenanthrene (3 rings), Pyrene (4 rings) and Benzo(a)Pyrene (5 rings), all included in the list of 16 PAHs priority pollutants. Soils were aged for two months before oxidation treatment.
Reactions were conducted without pH adjustement, using PTFE 50 mL centrifuge tubes as reactors, stirred isothermally at 20 ºC in an orbital shaker. Ratio selected for aqueous phase to soil was 2 mL•g-1. It has been studied the removal efficiency of every pollutant (Anthracene, Phenanthrene, Pyrene and Benzo(a) pyrene) with persulfate activated by Fe (II), Fe (III) combined with humic acids, granular ZVI, nanoparticle ZVI. Besides, the evolution of the different species (oxidant, surfactant, total iron in solution and contaminant) as well as pH, was followed during the reaction time and the identification of oxidation products and intermediates was carried out.
RESULTS
Effect of humic acids
It were found, after 5 days, higher removal efficiencies for all PAH when Fe (III) + humic acids were added than Fe (II). However, in both cases phenanthrene was the PAH with showed lower removal efficiencies. Furthermore, given the best results, activation with Fe(III) + humic acids was selected to be compared with ZVI activation for longer, due to the fact that there was an important quantity of remaining persulfate in the media.
Effect of surfactant
The presence of surfactant (sodium dodecyl sulfate) offered better removal efficiencies for all PAH. In this sense, despite being a competitor for the oxidant, as well as the pollutants, the enhancement of the mass transfer to the aqueous phase improved the removal efficiency for each PAH.
Effect of particle size
Comparing the effect of granular ZVI and nanoparticle ZVI, no significant differences were observed regarding removal efficiencies for all PAH. Anyway, after 40 days of reaction, it was observed a complete conversion of the contaminants.
Effect of nanovalent ZVI concentration
In this case, although almost complete removal efficiencies were achieved, when nanoparticle ZVI was used, less time was needed for the achievement of these conversions.
Oxidation intermediates
In some reactions, at intermediate times, it was observed the presence of anthraquinone, typical toxic compound found during oxidation processes of PAH [3].
REFERENCES
[1] Environmental Protection Agency, Polycyclic Aromatic Hydrocarbons (PAHs).
[2] ZHAO et al. Effect and mechanism of persulfate activated by different methods for PAHs removal in soil. Journal of Hazardous Materials. 254– 255 (2013) 228– 235.
[3] Liao et al. Identification of persulfate oxidation products of polycyclic aromatic hydrocarbon during remediation of contaminated soil. Journal of Hazardous Materials 276 (2014) 26–34.
ACKNOWLEDGEMENTS
The authors acknowledge financial support from the Comunidad Autonoma de Madrid provided throughout projects CARESOIL (S2013-MAE-2739) and from Spanish Ministry of Science and Innovation, projects CTM2010-16693 and CTM2013-43794-R.
KEYWORDS: Innovative Tender Procedure, Laboratory Tests, Activated Klozur® Persulfate,
Fully Automated ISCO, Hydrocarbon Fuels
ABSTRACT:
Overview
A marshalling yard for trains has been contaminated as a result of leaks, spills and filling losses of hydrocarbon fuels. An in situ remediation by Biosparging, Bioventing and Nutrient dosing has been carried out in the period from 2004 to 2010. After remediation for an amount of half a million Euro, a large residual TPH contamination remained in the soil.
Innovative Tender Procedure
An additional remediation effort was contracted in an innovative tender procedure under conditions of fixed price, time, removed mass and payment.
There were two selection criteria. For a fixed budget of a quarter of a million Euro, the contractor should indicate how much mass he demonstrably will remove (70% score). The plan of approach has been tested the feasibility (30% score). A number of contractors have put forward a smart solution. But there were also contractors who have decided not to make an offer.
Considerations and choice-based approach to remediation of a sub area
The main part of the pollutant load was located in the range from 14.5 to 18.5 m below ground level and comprises 47.9% of the overall load. This mass was situated in the top of the saturated zone and is more readily available to biological and chemical in-situ remediation techniques then contamination in the unsaturated zone.
Laboratory tests
By linking the results of an aliphatic aromatic TPH split group with substance group properties, a mathematical insight is obtained into possible remediation techniques. It was found that 43% of the oil is soluble in water and that more than 84% of the contamination is moderately aerobically biological or chemically degradable.
A desk study indicated that chemical oxidation would give the best results with activated sodium persulfate. On a laboratory scale, tests were carried out with alkaline activated persulfate and hydrogen peroxide activated persulfate. The hydrogen peroxide activated persulfate showed a decrease of 38-54% in the ground. However, the TPH was almost completely mobilized to the aqeous phase. Treatment with alkaline activated persulfate showed a destruction of 49-54% of TPH in the ground, with 10 times less mobilization of TPH to the water phase.
Full-Scale Application
The Full-scale remediation was carried out using a fully automated remotely controlled ISCO unit. The unit ensures complete telemetric monitoring, operating 24 / 7. Essential parameters, such as the injection pressure, the amount and flow rate of injection as well as the soil temperature were monitored continuously.
During the first injection period, an amount of 6.260 kg alkaline activated Klozur® persulfate, was injected over 15 ISCO injection wells in the most polluted areas.
Application of chemical oxidation with activated Klozur® persulfate leads to an increase in the pH, the redox potential and dissolved oxygen levels.
Comparison of the pollutant load after completion of the chemical oxidation with the load prior to the chemical oxidation, is showing a decrease of 49% of TPH in the ground.
A strong mobilization of product into the aqueous phase was not observed.
A second activation of the remaining Klozur® persulfate will be performed later this year, followed by a phase of enhanced aerobic bioremediation.
Conclusions
The innovative tender procedure has led to a smart solution, according on a ISCO approach with activated Klozur® persulfate based on the results of a bench scale treatability study.
It has been shown that bench scale testing is an indispensable tool in designing ISCO projects.
The bench scale treatability test and full scale field results correspond to each other.
After the first injection period of ISCO treatment was applied the TPH-concentration levels were successfully reduced with 49%.
Barium ferrates for in-situ chemical oxidation of BTEX contaminants
Christine Herrmann, Karin Hauff, Norbert Klaas
University of Stuttgart, VEGAS, Pfaffenwaldring 61, 70569 Stuttgart, Germany
Ferrate(VI) has a high oxidizing capacity - under acidic conditions, its redox potential is even higher than the one of ozone - making ferrate(VI) a very promising agent for water and wastewater treatment processes. It has been shown that various types of organic compounds like for example phenol or thiourea can be oxidised by ferrate(VI) [1].
The work presented here is especially focusing on the potential applicability of barium ferrate for in-situ groundwater remediation. To the best of our knowledge currently no material, except for oxygen-releasing compounds being applied for in-situ bioremediation, is tested for passive oxidative remediation. Since barium ferrate offers slow-release properties it could be utilized to form zones of strong oxidation potential with the possibility of producing a depot-effect in the aquifer. BTEX contaminants (benzene, toluene, ethyl benzene, and xylenes) represent one major category of contaminants affecting groundwater [2] and hence have been chosen as target pollutants to study the use of barium ferrates for in-situ chemical oxidation.
Ferrates(VI) can either be prepared by dry oxidation, wet oxidation or electrochemically. Here, the electrochemical preparation is used because it offers several advantages like for example a shorter synthesis time and reduced costs [3]. The electrochemical synthesis of ferrate(VI) is based on the oxidation of an iron metal anode in alkaline media [4]. Barium ferrate is obtained by subsequent precipitation and characterised by titrimetric chromite analysis [5] and X-ray diffraction. In order to investigate the reactivity of barium ferrate towards BTEX contaminants batch tests have been conducted using toluene as a model contaminant. The results will be presented along with considerations towards the potential applicability of the material for field application, including aspects of a later remediation technology.
“The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n°309517."
[1] M. Alsheyab, J.-Q. Jiang, C. Stanford, Journal of Environmental Management 2009, 90, 1350.
[2] P. Panagos, M. V. Liedekerke, Y. Yigini, L. Montanarella, Journal of Environmental and Public Health 2013, 2013, Article ID 158764.
[3] X. Yu, S. Licht, Journal of Applied Electrochemistry 2008, 38, 731.
[4] S. Licht, R. Tel-Vered, L. Halperin, Journal of the Electrochemical Society 2004, 151, A31.
[5] S. Licht, V. Naschitz, L. Halperin, N. Halperin, L. Lin, J. Chen, S. Ghosh, B. Liu, Journal of Power Sources 2001, 167.
Background/Objectives
Sodium persulfate is a widely used and accepted remedial strategy, however, the geochemical and physical conditions present in soil and groundwater are often overlooked when selecting an appropriate activator. The persulfate anion alone has the thermodynamic strength to react with organic target compounds but activation either alkaline, iron, hydrogen peroxide, or heat is required to generate the sulfate radical, which is preferred for efficient and kinetically meaningful reactions. Ambient activation methods have been employed at petroleum sites, with the understanding that ferrous iron naturally present in a reduced aquifer is contributing to activation, however, the influence of temperature is often overlooked. At a site in Arizona, sodium persulfate was injected in a groundwater aquifer with very low concentrations of iron (2-3 mg/L), relying on elevated injection fluid and groundwater temperatures (greater than 20 degrees Celsius) as the most prevalent activation method for activation using sodium persulfate.
The impacts at the site are petroleum-related hydrocarbons, with benzene as the primary remedial driver, observed at concentrations up to 2,800 µg/L in the study area. Two injection events were completed at the site to: (1) confirm lateral and vertical reagent distribution and related hydraulic properties, (2) obtain sodium persulfate persistence and consumption rates, and (3) assess the effectiveness of ambient activated in situ chemical oxidation (ISCO) at the site.
Approach/Activities
Two injections of 8,950 and 14,500 gallons of sodium persulfate solution were completed during the summers of 2011 and 2012. Groundwater within the injection area was monitored during and after each injection for approximately eight months.
To assess the transport, persistence, and consumption rates of the sodium persulfate in-situ during the first injection, a groundwater tracer (deuterated water) was used to distinguish between reagent consumption and washout as well as to determine sodium persulfate half-lives. Deuterated water was selected as a tracer for this application as it is very conservative and non-reactive with either sodium persulfate or the aquifer materials and non-toxic at the applied concentrations.
Results/Lessons Learned
The injection solution showed relatively consistent vertical and lateral distribution around the injection well. The kinetic reaction rate was relatively rapid, and as a result of the injections benzene concentrations declined by an average 80% from baseline concentrations. The data shows that at sites where groundwater temperatures are elevated naturally, ambient activation of sodium persulfate is a viable method for oxidation of benzene, and may play a more significant role than activation by background iron in either soil or groundwater.
Program:
• Who’s poo is this? Making the most of instant bacteria confirmations | James Taylor (ALS, UK)
• Pollution source tracing using isotope ratios | Douglas Baxter (ALS Scandinavia)
• Turnkey solutions with Trap & Treat® in situ remediation technologies´ | Palle Ejlskov ( Ejlskov A/S, DK)
• Water supply in urban areas with many well-known pollution sites – two cases in the Copenhagen area | Kristian Bitsch (Ramboll, DK)
• Questions and discussion
In order to establish sustainable post-mining vegetation during the re-development of mining areas, an understanding of the fraction of potentially toxic trace metals in the soil substrate that are available to plants is crucial. Mine soils in climates with high rainfall will be depleted in the easily available/soluble fraction by washout. Meanwhile, the metal fraction associated with the reducible fraction is unlikely to be released in the oxidising conditions of the surface environment. However, the oxidisable fraction of metals present in mine soils provides a potential reservoir that may be released into the environment when sulphide minerals with which the metals are associated weather in the oxidising surficial environment. This paper presents a relatively simple test that can be used to rapidly assess the oxidisable plant bioaccessible fraction of metals in a soil, along with results obtained from the test on soils sampled from a case study site contaminated with historic mine waste.
Phytomining technology (recently called agromining) is based on the ability of hyperaccumulator plants to extract and accumulate metals from soils. Especially, nickel hyperaccumulators are able to store ca 10 g Ni per kg of dry biomass. These plants are grown on ultramafic soils, which have a high Ni content and a low fertility. With suitable agronomic conditions, it is possible to obtain yields of 110 kg Ni per ha. Biomass is harvested, dried and incinerated to provide ashes, which is a high-grade bio-ore since they contain 15 -20 wt % Ni.
A process to generate high value Ni salts from the ashes has been developed (Barbaroux et al., 2012; Zhang, 2014). In particular, a salt called ANSH (ammonium nickel sulfate hexahydrate) is prepared from the ashes of the hyperaccumulator Alyssum murale grown in Albania. This salt can be used in metal surface treatment. As the major elements in the biomass are nickel, potassium, calcium, magnesium and iron, the subsequent operations are performed: ash washing to remove potassium, acid leaching, magnesium and iron separation, ANSH crystallization, dissolution and recrystallization. The final product has a purity higher than 99%.
This process has been up-scaled to the pilot scale. The designed pilot includes several jacketed glass reactors (from 2 to 12 L), a heating / cooling bath, filtration devices and pumps. This set-up enables us to produce ca 1 kg of ANSH from 1 kg of raw ash. The experimental details as well as the mass balances on the major elements will be presented, as well as the water and energy balance on the process. The fluxes of by-products will be given as well as propositions to re-use them.
A life cycle assessment is currently done, from the scenario of the overall chain (from the plant to the final product). The process will be compared to the production process of the ANSH salt by Ni-ore mining and hydrometallurgical process. The environmental impacts of both processes will be compared.
Acknowledgements: This work was funded by Institut Carnot Environnement Energie Lorraine (ICEEL), by China Scholarship Council (CSC) and Bpi France.
References:
Barbaroux, R.; Plasari, E.; Mercier, G.; Simonnot, M. O.; Morel, J. L.; Blais, J. F. A new process for nickel ammonium disulfate production from ash of the hyperaccumulating plant Alyssum murale. Sci. Total Environ. 2012, 423, 111–119.
Zhang X, Houzelot V, Bani A, Morel JL, Echevarria G, Simonnot M-O. Selection and combustion of Ni-hyperaccumulators for the phytomining process. Int J Phytoremediat 2014; 16: 1058-1072.
Brownfields threaten soil and (ground)water resources, and cause environmental & health risks as well as economic and social charges. In this context, “megasites”, large and complex contaminated brownfield sites, are a challenge for the development of effective strategies of investigation, clean-up and decision making. Regarding characterization studies, analytical chemistry generally focus on compounds with regulatory limits in order to measure how much contaminant is present, and not to provide information regarding the source of the contamination. On the contrary, environmental forensics investigations are devoted not only to describe pollution importance and distribution, but to identify former industrial practices and ulterior weathering processes linked to the current pollution in the site. In this sense, a possible strategy is the search for compounds, elements, isotopic signatures and/or molecular-markers that are diagnostic to be useful as tracers.
The LIFE+ I+DARTS project (Innovative and Demonstrative Arsenic Remediation Technologies for Soils, 2012-2016, www.lifeidarts.eu) is aimed at the recovery of soils contaminated with arsenic and heavy metals in former mining and industrial sites included in the Spanish inventory of polluted soils. One of the brownfields studied is known as Nitrastur (located in Langreo, Asturias, northern Spain). It was one of the main fertilizers plant in Spain for more than fifty years until its abandonment in 1997. The total surface of the affected site is 20 ha, and at least another 20 ha should be considered outside the main parcel, given that the surroundings have been affected by the historical activity of other heavy industries (ferrous metallurgy, coal thermal power station, chemical industry, etc.). In this site, we have carried out a detailed environmental forensics study to obtain a conceptual model for risk assessment and for the selection of clean-up strategies. The main tools used and a summary of the foremost results obtained, are the following:
• Five different types of pure waste (three inorganic: pyrite ashes and two types of slags, and two organic: spilled fuel and coal waste) were identified as the main pollution sources. Thus, a comprehensive chemical and mineralogical characterization of these products was carried out. As a result, and given their wide distribution and chemical contents, pyrite ashes, comprising mainly oxides and hydroxides of iron and other metal(loid)s, were considered the most problematic one. This waste was produced as a by-product of toasting sulphur ores, that were used in the former industrial activities to produce sulphuric acid subsequently used to manufacture ammonium sulphate fertilizer.
• As a consequence of pyrite ashes dumping, soil pollution is mainly composed of As and Pb, while Zn and Cu are considered secondary contaminants, all of them showing with levels higher than 1.000 ppm in many samples, and above 5.000 ppm in hot spots. Although inadequate waste disposal was also detected concerning other materials (slag, coal waste, etc.), only pyrite ashes had significant As and heavy metal contents capable to affect dramatically soil quality. In this context, the origin of the contamination has been verified by determination of Pb isotopic signature, and by the geochemical association of As with Sb and other trace elements determined by means of multivariate statistics methods.
• Distinctive forensics tools such as fingerprinting of weathered hydrocarbons spilled, and PAHs diagnostic ratios have revealed the co-occurrence of organic contaminants in some areas within the site.
• The soil affection is high in about 25% of the total surface of the site; this means that many areas could be considered initially free of pollution. Conversely, the subsoil of several buildings (classified as industrial heritage) was filled in the past with pyrite ashes.
• Groundwater is also affected especially wherever a thick layer of pyrite ashes (sometimes more than 2 m) is found. The amount of water in the alluvial aquifer, together with the low permeability of the buried waste, promotes only punctual affections as it was revealed by means of a high-resolution groundwater study. All things together, the potential mobility of the contaminants was determined to be quite low (chemical speciation and sequential extraction analyses were also made).
On the whole, the forensic study demonstrated the presence in high concentrations of a variety of contaminants affecting soil and groundwater quality. However, the low mobility of the main contaminants, the limited extension of polluted groundwater, and the high background levels in the surroundings suggest that sustainable clean-up technologies such as phytoremediation and bioremediation could be applied, at least partially; therefore supporting remediation costs optimisation strategies for the megasite.
Region Zealand works with remediation of contaminated sites in the Zealand area, Denmark. This includes construction of facilities that protect nearby residential areas against leaking gas from abandoned and closed landfills. Collection and utilization of methane gas from landfills for electricity production changes a pollution problem and a potent greenhouse gas to a sustainable energy source.
In Region Zealand there are a large number of closed landfills with varying kinds of waste. The majority of these sites contain organic waste in the form of household waste, garden waste o.a. with organic content. The production of methane gas normally will be at the highest shortly after the landfill is closed and the supply of waste is stopped - but the production of gas will continue for decades.
Methane gas is a potent greenhouse gas. The effect on the atmosphere is app. 20 times the effect of an equivalent amount of CO2. Collection and destruction of even small amounts of methane gas from landfills therefore may be of importance to the overall CO2 accounts. If the content of methane is high enough the gas could be used as an energy source to generate electric power directly to the grid.
Remediation of methane gas from closed landfills allows the following advantages:
• protection of all buildings located on or near the closed landfill
• reduction of growth retardation for plants and crops
• capture of methane gas that otherwise escapes to the atmosphere
• reduction of the greenhouse effect by changing methane to CO2
• combustion of methane as an energy source to generate electricity
• displacement of "black electricity" in the grid by "green electricity" from the remediation plant
In 2014 Region Zealand set a plant in operation to protect a nearby residential area against leaking methane gas from Stengaardens Landfill app. 50 km west of Copenhagen. In addition the plant was constructed to show to which extent it is possible to utilize methane gas for electricity production from landfills with limited methane production.
Stengaarden Landfill is placed in a former gravel pit and was active in the period 1972 to 1984. Extensive investegations of the site have shown large amounts of organic waste from households to a depth of 10 to 18 m. The methane gas was measured in concentrations up to 40 - 60% at the site. Studies have also shown that the methane gas has spread to a neighboring residential area.
To secure the residential area there has been established a total of 15 remediation wells in this part of the site from where the gas is collected in a manifold and fed through a vacuum line to the remediation facility. A dual-fuel diesel engine is burning the methane gas and uses the energy in production of electricity.
After 0.5 years of operation the content of methane in the gas to the remediation plant shows to vary from 20% to 25% vol. The dual-fuel engine generator system may be fed by an average of 35.9 Nm3/h of this gas mixture. The average power produced with the dual-fuel system in this first period of running is just about 26 kW/h. Of these totals, 81% of the energy comes from the methane gas and 19% comes from the support fuel of diesel.
Calculations of the efficiency for the dual-fuel motor-generator system shows that methane content as low as 9-12% in the gas would be the break even point for using the diesel more efficiently as an energy source for standard power production rather than as a support fuel in the remediation plant.
The experience from Stengaarden Landfill shows that use of only a minor part of the methane gas from this location can produce electricity equivalent to the power supply for a small village of about 30 houses.
Phytoremediation is a low-cost land remediation technology suitable for the clean-up of metal(loid) contaminants. The disposal of large volumes of biomass derived from phytoremediation is recognised as a technical and financial barrier that limits the wider application of this technology. Previous studies suggest using thermo-chemical biomass to energy technologies, e.g. gasification to address the waste disposal problem in addition to energy production.
Research is need to understand the solid-to-gaseous phase transformation of elemental contaminants during the thermo-chemical process, in order to recover elements from the process ash and prevent toxic emissions.
In this study, proximate and ultimate analyses were performed on six plant species collected from a contaminated site. Concentrations of 17 elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se and Zn) were determined in plant biomass using ICP-MS. Using thermodynamic and phase equilibrium software (MTDATA), the analytical data allows modelling of the solid/gas transformation of metal(loid)s during gasification.
The modelling results indicate the fate of metal(loid) elements during typical gasification conditions and how these are influenced by metal(loid) composition in the biomass and operational conditions.
As, Cd, Zn and Pb tend to transform to their gaseous forms at relatively low temperatures (<1000 oC). Ni, Cu and Co converts to gaseous forms within the typical gasification temperature range at >1000-1200 oC. Whereas Cr, Al, Ca, Fe and Mg remain in solid phase at higher temperatures (>1200 oC). Simulation of pressurised gasification conditions shows that higher pressure increases the solid-to-gaseous phase transformation temperature.
A clear theme arising from EPA’s optimization studies is the need for more accurate characterization of site conditions to ensure remedy efficiency and success. The goal of the session is to share our lessons learned, discuss opportunities and challenges with professionals in the audience and to gain insights from the experiences of others.
This session will present an overview of efforts to “optimize” site characterization, including leveraging the use of existing site data, the importance and application of a “life-cycle” Conceptual Site Model (CSM), the use of high resolution site characterization techniques to improve the design and implementation of groundwater remedies, the use of incremental sampling methodologies to improve the representativeness of characterization of soils, and the use of newer visualization tools to better plan and monitor site cleanup.
1. Background
Many countries have developed contaminated land management policies to reduce risks to humans and ecosystems originating from soil pollution. One of the major pathways of exposure for humans is inhalation of indoor air as a result of sub-surface contamination with volatile chemicals, called vapour intrusion (VI). Predicting the soil air and indoor air concentration as a result of soil pollution, and the related human exposure, is complex and is affected by numerous factors. Most of the present algorithms for VI calculate point estimates based on a set of default parameter values and therefore give no indication of the variation and conservatism of the predicted air concentrations.
2. Aim
A probabilistic assessment with sensitivity analysis is presented for 6 commonly used VI algorithms. In addition the deterministic default parameter set of each of the algorithms is evaluated against observed air concentrations (benzene, ethylbenzene, trichloroethylene) for accuracy, and against the probabilistic predicted range for the level of conservatism. The screening-level algorithms are ranked according to accuracy and conservatism in predicting observed soil air and indoor air concentrations to determine their suitability for regulatory purposes. To determine the periodization for further actions such as additional measurements or remediation, dominant parameters that drive the predictions, are grouped by physic-chemical, soil or building parameters, and by parameters that are either uncertain or variable.
3. Conclusion
According to this study, the screening-level algorithms that have a higher degree of conservatism for their default parameter set are the Johnson and Ettinger model (JEM), Dilution Factor algorithm from Sweden (DF SE), Vlier-Humaan and VolaSoil. From these 4 algorithms the JEM and VolaSoil have a relative high accuracy (discriminative power). For the latter two algorithms different parameters, that are variable and uncertain, contribute to the variation in indoor air concentration. Differences between parameters that drive the variation were observed between the aromatic and chlorinated hydrocarbons. For trichloroethylene, the default parameter set of Vlier-Humaan, CSoil and DF SE should be adapted to arrive at a higher deterministically predicted indoor air concentration when a more conservative approach is required. The deterministically predicted air concentrations for benzene and ethylbenzene seem to be sufficiently conservative. It is shown that the probabilistic approach allows for an improved insight into the relative importance of parameters in the risk estimates.
4. Reference
Provoost J, Reijnders L, Bronders J, Van Keer I, Govaerts S (2014). Probabilistic Risk Assessment for Six Vapour Intrusion Algorithms, Journal of Environment and Pollution, vol. 3, No. 2, 2014, ISSN 1927-0909 (print), ISSN 1927-0917 (online), Canadian Center of Science and Education, Toronto, Canada, http://dx.doi.org/10.5539/ep.v3n2p1
Assessing whether hydrocarbons in indoor air on an oil polluted site originate from the soil pollution or from effects or materials in the building is often challenging. Danish threshold values for indoor air are applicable for oil-hydrocarbons emanating from the soil pollution. The common analytical methods for indoor air samples usually give results for TVOC and BTEX. Household effects, building materials, smoking etc. do however also contribute to hydrocarbons in indoor air. The risk related to intrusion of volatile organic compounds from oil contaminated soil or groundwater will therefore on the basis of indoor air samples most often be overestimated.
The presentation will propose a sampling and analytical method that assists in determining the origin of hydrocarbons in indoor air, so that we can choose the appropriate mitigating measures.
Results from 6 indoor air investigations will be presented. 5 of the cases deal with oil polluted soil under houses/buildings that may pose a health risk to the people living in the house. In some of the cases indoor air quality has been monitored over a longer period. One of the cases investigates a bad smell that is suspected to originate either from an old soil pollution with oil and petrol or from a damage caused by a water leak.
Indoor air sampling is carried out on ATD-tubes over a period of 14 days. Analysis is performed by traditional GC-MS resulting in quantification of TVOC and BTEX.
Moreover an extended GC-screening is carried out to identify and quantify the specific hydrocarbons in the samples.
Petrogenous hydrocarbons have been detected in all the indoor samples, but substantial concentrations of hydrocarbons that are not of petrogenous origin have also been detected.
First part of the assessment is to distinguish petrogenous hydrocarbons from non-petrogenous hydrocarbons. Non-petrogenous hydrocarbons are then grouped according to their possible origin i.e. it is determined whether they come from smoking, painted surfaces, household goods etc. Lastly it is assessed if the products containing non-petrogenous hydrocarbons also contain petrogenous hydrocarbons, and in this case whether data exist that confirm the quantity of hydrocarbons that volatilize from the products to indoor air.
The results of the analysis and assessment are then compared with historical knowledge about the soil pollution and with the results from the soil and groundwater investigation. On this basis it is assessed whether or not the soil and groundwater oil pollution contributes significantly to hydrocarbons in the indoor air in concentrations above the threshold values.
In some of the cases it has furthermore been assessed whether the non-petrogenous hydrocarbons are present in concentrations that may pose a health risk.
The extended analyses of the indoor air samples has proven to be a good and relatively cheap way of assessing the origins of hydrocarbons in indoor air, and assist in making better decisions regarding potential remedial actions towards indoor air quality.
The purpose of this study was to provide a content analysis of 348 vapour intrusion (VI) articles published between 1966 and 2014. The research design utilizes computerized text mining content analysis to determine the major themes and concepts in the VI corpus and allows for an analysis of concepts over time, as well as emerging areas and needs for further research.
The results demonstrate that the major themes and concepts are in descending order [1] soil (air concentration), [2] model (parameters), [3] diffusion (coefficient), [4] site, [5] (volatile) compounds, [6] (ground) water, [7] risk (assessment), [8] house (construction), [9] uncertainty, [10] monitoring and [11] (hazardous) waste. Emerging areas of research are probabilistic risk assessment of software model parameters with Monte Carlo analysis (uncertainty), how hazardous waste is related to the site and sampling, monitoring and the remediation of ground water, (ad)sorption and equilibrium phase distribution in the water phase and the need to clarify the mass transfer and transport of contaminants, including the diffusion through the boundary flux layer. Several publications are questioning generally accepted ways in which VI is modelled, like for example the use of the Henry concept for calculating the soil air concentration.
This study contributes to the insight in the direction of VI by examining the changes in the literature. The results from this study suggest that changes on VI research are continually changing and will continue to evolve. It is thus possible to track the evolution of science by looking at semantic relationships and clusters of words.
Introduction:
In the last few years it has been observed, that the sewer system often is the primary intrusion pathway for volatile organic compounds (VOC) from contaminated groundwater or soil gas to indoor air. The sewer-system is a major intrusion pathway in more than 20% of the contaminated drycleaner sites in Central Denmark Region.
The indication parameter for intrusion of VOC by the sewer system is higher concentrations of VOC on the upper floors than on the ground floor or substantial higher VOC concentration in indoor air than estimated from concentration in sub slab soil gas.
Issue:
Intrusion pathways from VOC source to indoor air:
• Contaminated groundwater penetrates the sewer system and VOC evaporates to the air-phase in the sewer. The VOC can be transported by the sewer, driven by the pressure differential or the water flow
• Contaminated soil gas penetrates the sewer system, and the VOC can be transported by the sewer, driven by the pressure differential
• Sewer shafts acts like a chimney (causes depressurization), and draws contaminated sewer-air into homes
• Contaminated air from the sewer intrudes to indoor air through leaks in the sewer-system or through water traps (such as U-bends and S-traps)
• Sewers no longer in use are often a VOC spreading highway. Often they are in a poor condition, they are out of sight, and occasionally their existence is simply unrecorded.
The intrusion of VOC from sewer systems to indoor air is detected by air measurements in sewer wells, sewer-pipes and –shafts, over the water traps, and by measurements of pressure differential form the sewer to indoor air.
Remediation:
In many cases a very simple remediation method is useful to prevent intrusion of VOC from the sewer to indoor air.
Remediation methods could be:
• Depressurization of the sewer system to ensure that the pressure difference is from the indoor air toward the sewer.
• Sealing the sewer to prevent intrusion of contamination
The Central Denmark Region has remediated several indoor air problems by depressurization of the sewer system, and decreased the indoor air concentration up to a factor 200.
Presentation: At the conference, the intrusion pathways by the sewer system will be explained theoretically, and illustrated by case-studies, both for characterization and remediation. Strategies for measurements and measurement methods will be included.
Introduction: It is a well known fact that Volatile Organic Compounds (VOC) contamination in indoor air can be caused by evaporation from e.g. furniture, carpet, paint and wall paper. Often BTEX are the dominant substances.
With oil-contaminations under a house, it is often difficult to determine if the sub-slab contamination contributes significant to the VOC-concentration that has been found in indoor air, or if the indoor air concentration is caused by internal sources. It is important to know the source to an indoor contamination with VOC, to decide whether or not remediation of the sub-slab contamination is relevant.
With a blower door test, it is quite easily examined whether or not a VOC-content in indoor air is caused by sub-slab contamination, or by internal sources.
Methodology: A blower door test is a well known test in the building industry, to determine the tightness of a house. With a blower door test the pressure differential across the blower can be controlled, and thereby also the pressure differential across the slab.
When the pressure inside the house is lowered, there will be an upward pressure gradient across the slab, and both sub-slab contamination and internal sources will contribute to the VOC concentration in indoor air.
When the pressure inside the house is set higher, there will be a downward pressure gradient across the slab, and only internal sources will contribute to the VOC concentration in indoor air. The sub-slab contamination will not contribute significantly, due to the downward pressure gradient.
By doing indoor air measurements of VOC, under lower pressure (upward gradient over the slab) and under higher pressure (downward gradient over the slab), it can be determined if the sub-slab contamination contributes significant to the VOC concentration in indoor air. It is as simple as that!
Results: The method has been tested on a site in Central Denmark Region. On the site, there is a perchlorethylen (PCE)-contamination in soil and in soil vapor sub-slab, which causes a significant PCE-concentration in indoor air. There is no BTEX or TVOC contamination in the sub-slab soil.
In the test, indoor air concentration was determined by active sampling on carbon-tubes for both upward and downward gradient over the slab, and both with and without a gasoline can in the house. Sampling was conducted in 4 different places in the house with a pressure differential indoor/outdoor of +20, +5, -5, and -10 Pa.
The Blower door results were:
High Low High Low
Pressure Pressure Pressure Pressure
Benzene Benzene PCE PCE
With gasoline can 12 9 3 18
Without gasoline can 1 2 5 15
All numbers are listed in µg/m3, and each number is the mean value of 8 measurements.
The results show clearly, that the benzene-concentration is approximately the same with high and low pressure, but there is a substantial difference with or without gasoline in the house.
Correspondingly the PCE-concentration is high under low pressure (upward gradient) and low under high pressure (downward gradient).
Conclusion: The test shows that this method can be used to examine if VOC contamination in indoor air is caused by internal source or sub-slab source.
In the test there were only about 15 minutes between each sampling-cycle, and the sink contribution could have influenced the results. With longer time between the sampling-cycle, the results will probably be more significant. This issue will be tested further at another site before the conference.
The soil and groundwater at a textile manufacturing site in Flanders is polluted with chlorinated solvents. Trichloroethylene is found in the groundwater in very high concentrations (426 mg/l). Much less 1,2-dichloroethylene and vinyl chloride has been detected in the groundwater. The pollution in the soil is only trichloroethylene. A pure product layer has been detected at a depth between 7,2 and 7,6 m bgl. The soil consists of sandy clay and the permeability is very low. Practice has shown that the source zone can’t be removed by traditional techniques such as pump and treat. Excavation would be complicated because the pollution is situated near a building and at a great depth. To excavate the pure product layer expensive measurements are required. Because of this, excavation is not BATNEEC. In situ chemical reduction of the DNAPL by injection of ZVI (zero valent iron) may be a solution.
The chemical destruction of the chlorinated solvents by addition of ZVI was examined by VITO in lab tests. These tests proved a degradation of more than 95% at the dose that was selected for field application. After a period of 8 weeks, a carbon source to stimulate biodegradation was added. With the C-source, a further decomposition of the chlorinated solvents was achieved.
On large scale, it is often a problem to keep the iron in suspension during injection and to distribute the iron equally over the polluted zone because of the great density of iron and permeability limitations of the soil. To counter this problem, the iron was suspended in a guar gum slurry which was distributed in the subsurface by soilmixing. During drilling, the ZVI-slurry is injected under high pressure and mixed with the soil at the same time, creating a soil mix pile. At this particular case, a total of 14 soil mix piles were executed successfully until 8,4 m bgl, whereby 3500 kg of fine sized micro scale ZVI was applied. The guar gum will be biodegraded in time with release of simple sugars. This is expected to stimulate the anaerobic biodegradation of the chlorinated solvents, which would complement the chemical reduction by the ZVI.
The soil in the soilmix columns was sampled 12 months after soilmixing. The concentration decreased from 43700 mg/kg dm to 81,5 mg/kg dm. The concentration of iron in the soil is still high.
The groundwater concentrations measured until 12 months after soilmixing prove that trichloroethene is converted to the degradation products cis+trans 1,2-dichloroethene and vinyl chloride by the ZVI. Relatively high concentrations of ethene are measured. The groundwater and soil concentrations will be further monitored.
This pilot has already shown that soilmixing may be a promising alternative to injection of ZVI by direct push or by injection in wells. The soilmixing can be a solution for the treatment of chlorinated solvents in high concentrations in dense soils and at great depth without removing a lot of soil.
BACKGROUND
In Hagfors, located in central Sweden, a former by the state operated dry cleaning facility has led to a significant PCE contamination of soil and groundwater. A thermal treatment was performed about ten years ago, collecting around 5 000 kg of PCE from the unsaturated zone. However, later investigations have showed that both residual and mobile PCE DNAPL remains at larger depths and outside the thermally treated area. Today, the contaminants pose a threat to indoor air quality, as well as a nearby creek where some 100 kg of mainly PCE is being discharged per annum.
The facility is located upon esker material, explaining why the site geology consists of diversified layers of clay, silt, sands and gravel upon bedrock. PCE DNAPL occurs in both low conductivity soils in the unsaturated zone and all the way down to the saturated gravel upon bedrock at some 20 m below ground. Given the large depths and alternating high and low soil hydraulic conductivities, several in situ techniques are expected to perform poorly at the location. However, in situ soil mixing has been identified as a possible method to overcome reagent-contaminant contact issues associated with the subsurface heterogeneity in Hagfors.
In early 2014, a laboratory study has been performed in North America, where contaminated material from the Hagfors location has been mixed with bentonite clay and zero valent iron. The lab results indicate that a complete mineralization of PCE occurs in between 80 – 200 days, depending on iron type. In early December 2014 a pilot study is being performed at the Hagfors location, where it will be evaluated if soil mixing can be performed in situ down to a depth of 20 m using standard large format drilling rigs. The pilot test will involve 8 drillings, where different methods and tools for drilling, iron dosage, etcetera will be evaluated. Thereby, the pilot test has the potential to both refine and quicken the current standard operation protocol of the ZVI-Clay method.
AIM AND CONTENT
The aim is to present a case study and thereby to spread knowledge about a refined standard operation for the ZVI-Clay method to the audience. The presentation will include a project background, a description of the conceptual site model, a general introduction to the ZVI-Clay method and data from lab- and pilot tests.
RELEVANCE
The presentation may be relevant to administrative personnel (national regions etc.), consultants, entrepreneurs and others involved in the remediation of chlorinated solvents, but also other contaminants where different types of soil mixing is an option for enabling contact between contaminants and reagents.
In 2012 and 2013 Geo has been doing field scale remediation with stimulated reductive dechlorination on several sites in Denmark contaminated with chlorinated solvents. We have been using molasses as substrate and we have added the bacteria culture KB1® in order to increase the number of specific degraders on the sites. We have been observing degradation of the mother compounds PCE and TCE but we have also observed accumulation of the degradation products cis-DCE and VC.
To achieve full degradation of the chlorinated solvents there have been good experience with adding zero valent iron to the groundwater after SRD as a part of a treatment train. The method has been used following SRD with lactate as a substrate but as far as we know, the method has not been applied after SRD using molasses as a substrate as we have done.
The purpose with this lecture is to share experience with the method and show results from the field scale implementation of remediation by direct injection of nZVI slurry on three locations in Denmark.
Geo has been running batch tests in the laboratory where we have added nanoscale zero valent iron to PCE and TCE contaminated groundwater from 5 different locations where we have been conducting SRD with molasses as substrate. The batch tests showed positive results, and based on the results, we have been doing field scale remediation with direct injection of nanoscale zero valent iron slurry into the groundwater on three locations in Denmark.
The results from the batch tests showed in general increased degree of dechlorination (DOD%) when adding nZVI to the groundwater. In 11 out of 13 tests, the degradation rate increased more in the batches with nZVI than in the blind batches and there was measured a sustainably amount of ethen and ethane.
Based on the results from the batch tests we have injected nZVI on three locations in Denmark. The injections has been carried out as direct injections with a jetprobe by Geo, Arkil A/S and NANO IRON, s.r.o. The nZVI was delivered from NANO IRON, s.r.o.
The first results from one of the locations show increasing concentrations of VC, ethen and ethane and increasing DOD%, indicating that the chlorinated solvents are fully degrading. An example from one of the locations shows a DOD% on 10%-50% before remediation. After SRD with molasses as substrate the DOD% increased to between 40%-70% and after adding nZVI to the groundwater the DOD% increases to 60%-80% in the majority of the groundwater samples.
At another location we have injected nZVI in two areas. The plume close to the source area where we have been injecting molasses and bacteria 2 years before treating with nZVI and the plume area more downstream where we only have been injecting nZVI. In the hotspot area we measured a maximum concentration of sum of chlorinated solvent and their degradation products on 130 µg/l mainly composed of VC. In the plume we measured a maximum concentration of sum of chlorinated solvents and their degradation products on 180 µg/l mainly composed of TCE and DCE. The first results show that the chlorinated solvents has been degraded in the hot spot area after injection of nZVI but in the plume area we still measure concentrations of sum chlorinated solvents and degradation products up to around 90 µg/l mainly TCE and DCE. The results indicates that the pre-treatment with molasses increases the degradation rate.
We will show some illustrative results from the cases, and discuss advantages and also hurdles to overcome with this kind of treatment train in sandy aquifers.
Nanotechnology has special relevance to the in situ soil and groundwater remediation, due to the combination of nanoparticles properties with fluid characteristics and thus the potential for injecting nano-sized (reactive or adsorptive) particles into contaminated porous media (e.g. soils, sediments, and aquifers). Among the various nano-materials explored for remediation (e.g. zeolites, metal oxides, carbon nanotubes, etc) nanoscale zero-valent iron (nZVI) is currently the most widely used for the in situ remediation of soils from a variety of toxic pollutants (e.g. chlorinated hydrocarbons, nitro-aromatics, CrVI, etc). The nanoparticles are typically injected as slurries (nanofluids) directly into the subsurface to remediate contaminated groundwater plumes or contaminant source zones. A variety of coatings (e.g. polyelectrolytes, surfactants, polymers) and supports (e.g. carbon, silica) may be used to stabilize the nanofluids by increasing their resistance to particle aggregation and facilitating their delivery to target pollutants. There is a need to understand the interacting factors controlling the stability, mobility, and reactivity of nanoparticles when injected in saturated porous media. In this respect, the current study is breaking new boundaries as no systematic study has previously been made to specify the most suitable agents that ensure the stabilization of reactive nanomaterials and their successful delivery to the target pollutants within contaminated groundwater.
Aqueous suspensions of nZVI (nanofluids) are prepared by adding NaBH4 solution under anoxic conditions in an aqueous solution of FeSO4 7H2O pre-grafted with the following polymers acting as coatings: PAA-Na (sodium polyacrylic acid), CMC-Na (sodium carboxymethyl cellulose), CMC-g-PDMAM (carboxymethyl cellulose-g-polydimethylacryl amide), and PAA-g-PDMAM. The size distribution of nanoparticles (NP) is measured with dynamic light scattering (DLS) and transmission electron microscopy (TEM), whereas their stability is evaluated with sedimentation tests and measuring the ζ-potential. Per-chloro-ethylene (PCE) is used as model non-aqueous phase liquid (NAPL). To assess the nZVI reactivity with respect to dissolved and bulk NAPL, tests are performed in batch reactors, and mechanistic multi-step reaction models are developed to estimate all pertinent kinetic parameters.
Visualization studies in glass-etched pore networks enable us to identify the nanoparticle flow and reaction mechanisms at pore-scale. The transient NP sticking coefficient associated with the attachment/detachment of NPs is determined as a function of the pore blockage reflected in the “effective” water permeability. The accumulation of NPs in the water/free NAPL/solid contact line may change the interfacial tension and/or wettability by stimulating the NAPL detachment from the solid surface and leading to ganglia mobilization. Hence, it is of high importance to clarify if the free NAPL mobilization is not favored relative to NAPL reaction processes. The capacity of nanoparticles to dechlorinate the bulk and dissolved PCE under realistic conditions is tested with continuous flow tests in soil columns. To evaluate the capacity of NPs to remediate trapped ganglia of NAPL (source zone), the residual NAPL is created with successive drainage-imbibition displacement cycles at adjustable flow rates. The effluents from the tests are collected in fraction collectors, treated adequately (e.g. filtration, centrifuging, solvent extraction), and analyzed to measure the concentration of PCE or any other intermediate reaction product (e.g. TCE) with GC-ECD (Gas Chromatography-Electron Capture Detector) and the concentration of nZVI with atomic absorption spectroscopy (AAS).
A macroscopic numerical model is developed by coupling the reactive with multiphase transport and colloid filtration processes in homogeneous porous media. The model is used to estimate all pertinent parameters with inverse modeling of flow-through tests in soil columns. Finally, quantitative data concerning the nanoparticles mobility, longevity, and reactivity are used in a feedback mode to classify the nanofluids and suggest the most efficient ones for eventual pilot-scale studies.
DNAPL source zone treatment with ZVI soil mixing
Introduction: Dense Non Aquious Phase Liquid (DNAPL) source zone remediation remains a challenge. The known heterogeneous distribution of chlorinated hydrocarbons (CHC) and the formation of difficult to locate DNAPL pools and/or residual DNAPL makes the successful remediation of CHC source zones even more challenging.
Challenge: In the historic city center of a small town near Rotterdam (The Netherlands) the activities of a former dry cleaner led to contamination of soil and groundwater. The soil stratigraphy consists of mainly clay with heterogeneous distributed layers of peat and sand. The soil is contaminated down to 10 meters below surface with CHC (PCE, TCE, DCE, VC) which feeds a plume in the first aquifer. In order to make the site suitable for redevelopment the client was looking for a remedial solution that is capable of reducing the contaminant mass in the source zone in a short period of time and stops the distribution of the contaminants towards the plume.
Several remedial options for the source zone were evaluated such as biological treatment, chemical oxidation and excavation. All these remedial approaches were judged not feasible, because of the very sensitive historical buildings in close vicinity to the source zone, the soil stratigraphy and the probable presence of DNAPL as well as the wish of the client for rapid redevelopment of the site.
Approach: ARCADIS proposed soil mixing with zero valent iron (ZVI) as best option for the site and was granted the contract. This innovative technology combines the benefits of a chemical treatment with optimal reagent distribution. The application is vibration-free and fast. Since the reagent slurry comprised of a combination of ZVI and bentonite the introduced clay also assists in additional reduction of the permeability which subsequently leads to further reduction of leaching of residual contamination to the plume.
Result: Prior to the field application ARCADIS executed a feasibility study in order to develop an optimum reagent mixture. For the full-scale remediation, a double auger system best suited to the location specific constraints was developed. In a five weeks timeframe, 600 overlapping columns were drilled to treat the 1.200 m3 source zone. With the implementation of a thorough quality control protocol, issues such as ZVI quality and mixing performance could immediately be identified and corrected. Six months after application the contaminant mass in the treated soil volume was already reduced by more than 90% while further reduction is expected.
Presentation: We will present details of the applied ZVI soil mixing technology in general and for this specific urban site in particular. Also several issues that have to be taken into account during application will be further discussed..
Composting is a process known from ancient times which is widely used nowadays for the stabilization of biodegradable municipal/agro-industrial wastes and the preparation of organic fertilizers. A number of different organic materials can be utilized as compost substrates. The microbial consortia that develop in the composting pile during the process are responsible for the breakdown of organic matter as well as for the degradation of more amenable environmental contaminants (petroleum-derived products, monoaromatics, organic solvents etc.). In recent years the degradation of more persistent organic pollutants (PAHs, PCBs and chlorinated pesticides) during composting treatments has been proved.
In bioremediation practices, composting consists of mixing of polluted soils with typical compost substrates in order to achieve the decontamination/detoxification of such contaminated matrices. Although co-composting approaches have been already used for remediation at full scale (e.g. by the US Army for the treatment of TNT contaminated soils) in case of pollution with POPs there are still some limitations that needs to be overcome to make this an established technology.
This presentation will focus mainly on the tests performed to optimize the composting of PAHs contaminated soils so that it could be used in practice.
A first set of experiments was aimed at evaluating the suitability of various waste materials and mixtures for the co-composting of PAHs contaminated soils. Two different soils (1st ΣPAHs 370 mg kg-1, the highest concentration of pyrene and fluoranthene; 2nd ΣPAHs 6000 mg kg-1, the highest concentration of phenanthrene and anthracene) and 5 different organic waste mixtures were tested. The volume of each compost pile was approx. 0.75 m3 and the ratio of soil to organic waste was 1:1 (w/w dry basis). Compost piles were aerated by re-digging the whole content of composters 4 times a year.
Since the beginning of the experiment, temperature in the piles’ core, air quality and respiratory gases, were monitored continuously, while concentration of PAHs and microbial parameters (PLFA) were assessed during the thermophilic, cooling and maturation phase throughout a period of 2 years. When the concentrations of PAHs dropped significantly and composts were mature a battery of ecotoxicological and leachate tests was performed. These analyses proved that PAHs were degraded effectively during the composting process as their degradation in both soils varied from 95 to 98 % after 2 years (with more than 90 % of the initial PAHs content was degraded within the first year). Ecotoxicological tests suggested that no toxic metabolites were produced as there was no toxicity associated to the mature composts. According to our results, the composition of the organic waste does not play a substantial role on the extent of PAHs degradation if suitable humidity and carbon to nitrogen ratio are provided, although some differences in the rate of contaminants degradation were observed.
A second set of experiments was aimed at assessing the optimal organic waste to soil ratio. According to the literature, optimal volumetric ratio of soil to compost mixture in order to reach thermophilic conditions is around 30 %, but this is known to highly depend on the quality of both organic waste and soil. In addition, it is not clear yet whether it is necessary to reach the termophilic conditions in order to trigger PAHs degradation. Therefore, experiments were carried out in smaller volumes (150 l), in thermally insulated rotary composter. The organic waste that proved to be the most conducive to PAHs degradation in the previous test was selected along with a soil similar to 1st soil described above (with a slightly higher PAHs concentration, i.e. ΣPAHs 540 mg kg-1). The soil to compost substrate ratios tested were in the range of 10 to 50 vol.%. After 113 days of incubation, the residual concentration of PAHs ranged from 4 to 6% of the original concentration regardless of compost composition, while in the control microcosm (pure contaminated soil) it accounted to 80%. These results show that an efficient PAHs removal is achieved during composting even with a high soil to compost volumetric ratio (up to 50 vol. %). However, these tests were conducted in thermally-insulated composters, under ideal conditions and larger scale tests (0.75 m3 as described previously) are currently in progress. Preliminary results from these latest set up show that the degradation of PAHs is speeded up significantly, even in the presence of 65 vol.% of soil in the compost mixture compared to the control microcosm.
The project was supported by the Technology agency of the Czech Republic (project No. TE01020218).
The touristic magnet of the Valdemarsvik fjord lies on Sweden’s southeast coast in a geotechnically unstable area with high risk of landslides. For many years Valdemarsvik was the largest single source of chromium for the Baltic Sea area, producing about 250kg/year. That, and the now-closed Lundsberg Läder chromium tannery, created contamination that is being addressed today at this area of high importance for marine tourism, boating, fishing and bathing.
The Municipality of Valdemarsvik and the Swedish Environmental Protection Agency are financing the remediation of the fjord and awarded a €25M ($31.7M) contract to DEME Environmental Contractors (DEC) in January 2012.The project requires dredging the contaminated seabed in the inner part of the fjord, then re-using the dredged sediment at Grännäsviken, an onshore fill area.
The actual dredging went on in the course of 2013. From an area of about 350,000m2 with water depths ranging from 1-14m, DEC has removed all sediment with a chromium concentration above 500 mg/kg. About 200,000m3 of sediment has been removed. This will reduce future chromium discharge into the Baltic Sea by as much as 90%.
Given the unstable nature of the site DEC first installed 400,000 m of lime-cement pillars to a maximum depth of 22m near the shores in order to minimize the risk of settlement and landslides during dredging and landfill construction.
To meet stringent environmental demands dredging took place within silt screens to prevent turbidity outside the dredging area. Furthermore environmental dredging tools were applied to minimize the spill and the spill’s chromium content to below 20g/m².
Dredged sediment was transported by barges to the site Grännäsviken, where it was screened and stabilized with cement to obtain a shear strength of minimal 25kPa. The stabilized material was then used as backfill on the site.
Any water released from the sediments was treated for suspended solids and chromium VI by means of a mobile water treatment plant.
Excavation followed by landfilling is the most common method for treating soils contaminated by metals. Except from that landfilling is not sustainable in a longer perspective, potential valuable metals present in the landfilled masses are not utilized and returned into the societal cycle but left in the landfill with risks of future leaching. Thus, alternative treatment methods are needed. One interesting method is soil washing with metal recovery. By removing the metals not only valuable substances can be recovered but in addition the soil residues become cleaner. Earlier studies by our group on similar soil samples show that leaching using acidic waste process water efficiently release Cu from the samples and that the Cu can be recovered. In this project the method is further developed and evaluated. In addition a special focus has been on the soil residues in order to investigate how the proposed remediation method influences on the soil properties.
Soil samples strongly polluted with copper (Cu) were collected from two sites (A and B) in Sweden. The soil samples were washed with a strongly acidic process water. The leaching efficiency for Cu was optimized for the parameters liquid-to-solid-ratio (L/S) and dilution of the acidic process water. It was also indicated that in one of the sites sieving of the soil before leaching could reduce the amounts of soil needed to be treated, while in the other soil sample the Cu was more or less evenly distributed between different soil particles sizes. The final leaching parameters that were used in a scaled up batch experiment were; 30 minutes leaching time for the soil washing, L/S of 8, acidic process water diluted with milliQ water to 75/25. In order to release weakly sorbed metal ions the residues were thereafter washed with milliQ water.
The original soil from site A is classified as clayish fine sand/coarse silt, while the soil from site B is classified as slightly clayish sand and coarse silt. After leaching, the distribution between different particle types was slightly changed, but in general the soil residues were similar to the original ones. This was also confirmed by the scanning electron microscope SEM images. The pH values in the final soils were acidic and around 4. However, already in the original soils the pH values were <5. Based on these results the soil function “soil as filter and buffer for heavy metals” were evaluated using the TUSEC (technique for soil evaluation and categorization for natural and anthropogenic soils) manual. Originally the soil from site A was of class 5 i.e. “very low capacity of binding and buffering heavy metals”, while site B was of class 4 i.e. “low capacity”. After the soil washing remediation process both soils belongs to class 5. Consequently, the acidic leaching did not influence on the soil properties to a large extent.
After acidic leaching and water washing the Cu contents in the soil samples are reduced five times or more. However, the Cu contents in both soils still exceed the Swedish regulation for “less sensitive land use” (MKM) and cannot directly be put back to the former contaminated site. Instead they might be landfilled. The original soils cannot even be deposited in landfills for hazardous waste, while after treating the soils according to the proposed method the Cu leaching is decreased 6 times and the solid residues can be treated in landfills for non-hazardous waste.
To summarize, the proposed method clearly shows a potential not only to remediate Cu polluted soils but also to recover and reuse the Cu from the generated leachates. Even though the previously highly polluted soils cannot be directly put back at site the solid residues can be deposited in landfills for non-hazardous waste, which is an improvement compared to the original soils that cannot even be deposited in a landfill for hazardous waste.
Teresa Castelo-Grande1, Paulo A. Augusto2 and Domingos Barbosa1
1Laboratório de Engenharia de Processos, Ambiente e Energia (LEPAE), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
2Departamento de Ingenieria Química y Textil, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
Summary
An innovative environmental friendly technique, which combines supercritical extraction with carbon dioxide (CO2) and ultrasounds, is studied by applying it to the removal of atrazine from soil matrices. The obtained recovery for atrazine is higher than the corresponding values for supercritical extraction with CO2, and similar to the recoveries obtained when organic cosolvents are used. Besides high values of recovery, this new technique does not significantly affect the structure of the soil and does not leave any type of residue.
Introduction
Supercritical extraction (SCE) with carbon dioxide (CO2) has been suggested for the removal of hazardous substances from solid matrices and liquids [1-3], however, to increase the selectivity and the recovery of some types of contaminants, mainly polar substances, this technique is used with organic cosolvent (e.g., methanol and acetone). As SCE with CO2 is considered a environmentally friendly remediation technique, the use of organic cosolvents is a major drawback.
Ultrasounds have been used, mainly in analytical techniques, to enhance the extraction from natural products and other solid matrices [4-6]. These studies have been mainly focused in convencional solid-liquid extraction.The increase in the recovery by using ultrasounds is mainly due to the phenomena of cavitation, which consists in the formation, growth and collapse of gas/vapour bubbles in a liquid medium. This generates micro-turbulence and very high temperatures and pressures (close to 1000 atm and 5000 K) in the vicinity of these bubbles. Because supercritical fluids have densities close to that of liquids, we would expect a similar phenomena to occur in supercritical extraction.
To analyse this possibility, the supercritical extraction of atrazine from soil samples, with and without ultrasounds, was studied and the results compared.
Materials and Methods
This study was carried out in a semi-continuous supercritical extraction unit consisting of an extractor (with a capacity of 80 cm3), to which supercritical carbon dioxide was continuously fed at the specified pressure. The extractor is inside a thermostated air bath, to mantain the temperature constant, and has an ultrasonic transducer connected to its walls (this transducer is connected to an ultrasound generator). Each extraction essay lasts for 7-8 hours, and the range of temperatures and pressures studied were 303 – 333 K and 10 – 25 MPa.
The experiments were done with soil samples (30 – 35 g) impregnated with known amounts of atrazine, and the recovery of atrazine was quantified by HPLC.
Results and Discussion
The results obtained for the extraction of atrazine, with and without ultrasounds, are summarized in Figure 1 for an operating pressure of 24.5 MPa. This figure clearly shows that the use of ultrasounds enhances the extraction of atrazine leading to an increase of 60 – 80% in its recovery
Conclusion and References
A new environmentally friendly remediation technique for soils, which joins ultrasounds and supercritical extraction with carbon dioxide, is studied for the extraction of atrazine. This preliminary results show that this is a promising remediation technique for soils contaminated with pesticides and other hazardous substances, which does not affect the soil structure and does not leave any type of residues.
[1] J. Sunarso and S. Ismadji, Journal of Hazardous Materials 161, 1 (2009).
[2] G. Anitescu and L.L. Tavlarides, Journal of Supercritical Fluids 38, 167 (2006).
[3] M.N. Baig, G.A. Leeke, P.J. Hammond and R.C.D. Santos, Environmental Pollution 159, 1802 (2011).
[4] S.R. Shirsath, S.H. Sonawane and P.R. Gogate, Chemical Engineering and Processing 53, 10 (2012).
[5] E. Riera, Y. Golás, A. Blanco, J.A. Gallego, M. Blasco and A. Mulet, Ultrasonics Sonochemistry 11, 241 (2004).
[6] H. Bagherian, F.Z. Ashtiani, A. Fouladijatar and M. Mohtashamy, Chemical Engineering and Processing 50, 1237 (2011).
Acknowledgments
The authors would like to acknowledge the Centro de Biotecnologia e Química Fina (CBQF), of the Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Portugal, for the use of the supercritical extraction equipment.
The success of in-situ remediation strongly depends on the level of knowledge and a quality description of the geological structure of the contaminated site. Most failed applications of in-situ remediation technologies were based on successful laboratory and field pilot tests. The failure of the remediation methods is usually not a failure of the technology itself, but it is a failure of the insufficient description of the geological and hydrogeological conditions at the site. The basic conditions for successful remediation include a detailed description of contaminant distribution, proper understanding of the groundwater flow, a detailed geological description, a description of stratification and fracturation, a description of aquifer inhomogeneities, and an understanding of the directions and velocities of groundwater flow. In recent years, high resolution methods have been used for a very detailed description of the contamination as well as the geological and hydrogeological conditions. A complex of methods related to well-logging technology is a very effective system for high resolution diagnosis.
Some data obtained from well-logging cannot be obtained by other methods. Well-logging is irreplaceable from this perspective. One such group of data is used to clarify the groundwater flow in the borehole and clarify its relation with the geological and tectonic structure and the construction of the well. Using an appropriate set of well-logging methods we can determine depths of permeable layers and of open fractures in which there is a flow, it is also possible to measure the intensity of flow. The measurement can determine whether there is a flow across the borehole or whether there is water “short circuit” between two permeable layers. Well-logging can also be used to determine the groundwater flow direction. The advantage of well-logging is its ability to detect fast but also very slow flow: centimeters per day, and slower. If there is a group of wells at a location, it is possible to measure this group of wells to draw conclusions about groundwater flow not only in the wells themselves but also in the whole rock body. This method is widely applied to sites with contaminated groundwater. Based on the results it is possible not only to describe the current state of migration of the contaminated water (in favorable cases it is possible to also record the form of pollution i.e. water insoluble) but a fairly accurate estimate can be made of the further spread of the contamination plume. Well-logging thus provides important information that can be used in planning the optimal remedial method as well as during the actual remediation: in the risk analysis stage, during the remedial work and also in the course of monitoring after completion of the remediation.
This paper describes examples of measured data from sites and demonstrates the significance of well-logging measurements for a detailed understanding, enhancement and optimization of in-situ remedial systems. Detailed measurement and interpretation of natural conditions together with a detailed description of the contaminant distribution provide essential information for the design and dimensioning of the in-situ application of reactive agents and monitoring of in-situ remedial technologies. The presented data are from the interstitial soil environment as well as from a fractured bedrock site.
Acknowledgements: We would like to thank the TA ČR for their financial support (project No. TE01020218, research centre “NANOBIOWAT” and project FP7 No. 309517 “NANOREM”)
Introduction and Background
Groundwater in Denmark is an important resource, as more than 98% of the drinking water in Denmark is abstracted from groundwater. In addition Groundwater is used for irrigation, industry and livestock. Further groundwater plays an important role for groundwater-dependent nature areas, such as lakes, streams and wetlands in general.
The Regional Council of Central Denmark Region has launched the process of a Growth and Development Strategy for the period 2015-2030. The policy-based approach to ensure the development of society and business while ensuring consistency between, among others growth partnerships, government growth plans and municipal strategies. Four main areas has been selected, Competitiveness, Welfare, Demographics and Climate and Resources.
In connection with the climate and resource area in regional Growth and Development Strategy there is a need to examine the challenges and issues that are most important in connection to the exploitation of groundwater resources. The purpose of this analysis is to clarify the challenges, but also to describe the process to be implemented to achieve an appropriate long term management of groundwater resources. An important factor for being successful is to involve the key stakeholders and resource persons in the sector.
Central Denmark Region believes that clean groundwater is a fundamental prerequisite for growth in the region.
In Denmark there is a long tradition of understanding the groundwater recharge processes, aquifer flow, and resource deployment. This is a prerequisite for protecting groundwater, where it makes the most benefit and ensure that the resource is clean future. The work has traditionally involved a variety of actors, including research institutions, authorities, consulting engineers and water companies. During the last decade the mapping of the Danish groundwater resource has led to development of highly sophisticated methods for the identification, investigation and modeling of groundwater and water cycles in Denmark.
Approach
In order to explore the players' short-term and long-term challenges in the groundwater sector the survey seeks to make a survey partly to uncover main challenges and also the main and most promising opportunities for the development of the groundwater area for the benefit of the resource and its use.
The study is based on a series of themed half-open person interviews with selected people in and around the groundwater sector. Additionally conducted focus group interviews based on the statements in the interview round will be carried out.
Abstraction of groundwater for drinking purposes takes place in large and small waterworks. These are either embedded in a local environment or a portion of a larger unit which supplies a substantial area of water. The treatment of the water is based on simple techniques like sand filtering for iron and manganese removal. The Danish groundwater abstraction is built upon a political agreement that the water should be clean at the source.
Additional water treatment has been avoided by regulations on land use, remediation and moving the abstraction wells.
The individual consumer use water as it is delivered also for drinking water purposes. In industry, there may be special production processes which require special quality. For these purposes dedicated facilities which can be targeted individual needs is setup.
The exploitation and protection of groundwater involves a wide range of stakeholders. The survey of the main challenges and possibilities are analysed by interviewing relevant persons representing organisations in different part of the value chain.
Danish association of waterworks, Agriculture, water dependent businesses (Arla and Danish Crown) NGOs, Engineering consultants, Confederation of Danish industry, Municipalities, Regions, Danish Ministry of Environment, DG environment, Universities and research institutions.
Phase 1: Phase 2: Phase 3:
Data collection/interviews -> Analyse of interviews -> Qualification/group interviewing
Output and time line:
The survey will point out main areas to support for future growth of the groundwater sector in Denmark. It will give direction focus points for future development and enable the politicians to support this in future programmes and policies.
The data collection phase has been initiated and is expected to be finalised by the end of January 2015. The focus group interviewing will be carried out in February and the reporting made available in the middle of March.
The preliminary results from the interviews all ready carried out are related to water quality: 1. Emergent contaminents like PFC’s and pesticides; 2. Conflicts between groundwater protection, agriculture and city development and 3. Climate adaptation and risk of contamination of groundwater resource.
Ecosystem services of the groundwater and the subsurface; filling the knowledge gap
J. Lijzen, S. Vermooten, H.P. Broers, S. van der Meulen, M. Rutgers
In densely populated areas, the use of groundwater and the subsurface for functions such as groundwater extraction, aquifer thermal energy storage and infrastructure is increasing. This results in a need for subsurface spatial planning and careful consideration of the use of groundwater for several (economic) activities. When planning activities influencing the groundwater system, the relation between activities and Ecosystem Services (ESS) is useful to assess the sustainable use and impact and for weighing activities. Therefore, a) information of relevant ESS and related anthropogenic activities was generated, and b) a technical decision support framework was developed for the sustainable use of the groundwater system. The purpose of the information is to support the National and local authorities with knowledge and data in order to make informed decisions on the use of the subsurface and groundwater. For the definition of the ESS, the structure of CICES (2013) and MAES (2014) was used.
The consistent technical framework explains:
1. How anthropogenic activities depend on the ecosystem services;
2. The impact of these activities on ecosystem services;
3. Which activities could be combined or have an adverse impact on each other.
A set of factsheets summarizes all available knowledge about these relations and preliminary guidance for local and regional authorities for decision making. Nine activities (out of a list of 26) were selected and described: Drinking water abstraction from groundwater; Irrigation with groundwater; Aquifer thermal energy storage (ATES); Abstraction of salt groundwater combined with injection of brine; Subsurface storage of radioactive waste; Application of manure and pesticides; Nature conservation measures; Groundwater level management in polders; Remediation of historical groundwater contamination.
The knowledge gap of ESS for the subsurface and groundwater was filled, as until now little has been published on that matter in comparison to the ‘above-ground’ ESS. Eleven ecosystem services are defined for the groundwater compartment:
Provisioning services
1. Availability of sufficient water with specific quality
2. Energetic content
Regulating services
3. Attenuation capacity of the subsurface
4. Soil bearing capacity
5. Storage capacity
6. Bio-geochemical cycles (material and water cycles)
7. Temperature regulation
8. Providing surface water base flow and surface water quality
9. Upward seepage to groundwater dependent nature reserves
Cultural services
10. Cultural–historical and experience values
11. Biodiversity and habitat
These 11 ESS were described extensively. The processes that determine the performance of the service were described for each ESS, together with possible measures to optimize the ESS and the availability of data and indicators describing the performance of the ESS in the Dutch situation.
Currently a Structure vision on the subsurface is made by the National Government in close cooperation with local and regional authorities (MinIenM, 2014). Some of the generated data was already used in this process. On the basis of sustainable resource-driven management, priority can be given for example to scarce services. Similar priorities can also be drawn up using an assessment framework in which various forms of potential use are ranked according to what currently the government deems to be in the public interest.
Another important policy development is the National Ecosystem Assessment that has to be carried out within the context of the EU Biodiversity Strategy. Geographical data and maps on all ESS including the ESS related to the groundwater and subsurface are developed. The data in this project also contribute to that purpose.
References
- Broers and Lijzen. Afwegingskader grondwater Deltares-no. 1207762-016, RIVM-no 607710003/2014
- Lijzen en Vermooten, 2014 in preparation
- CICES (2013) Common International Classification of Ecosystem Services (CICES): Consultation on Version 4, August-December 2012 (Haines-Young R, Potschin M, eds.), EEA Framework Contract No EEA/IEA/09/003 (Download at www.cices.eu or www.nottingham.ac.uk/cem)
- Maes J, et al. (2013) Mapping and assessment of ecosystems and their services. An analytical framework for ecosystem assessments under action 5 of the EU biodiversity strategy to 2020. Publications of the European Union, Luxembourg.
- Min IenM, 2014. ‘Opgaven voor de ondergrond; Probleemstelling van het Programma STRONG, juni 2014 (Min IenM, 2014).
- EU Biodiversity Strategy (http://ec.europa.eu/environment/nature/biodiversity/comm2006/2020.htm
Soil and groundwater related ecosystem services in the Atlas Natural Capital
Suzanne van der Meulen (Deltares), Kees Hendriks (Alterra), Michiel Rutgers (RIVM)
The upcoming Atlas Natural Capital will provide a first large dataset about ecosystem services and natural capital in the Netherlands. Construction of the maps comes with many interesting challenges since translating soil and groundwater data into ecosystem services is not straightforward and has not been done before at such a large scale. While soil and groundwater is in many cases neglected in ecosystem services assessment, the atlas includes many maps that demonstrate services from the subsurface such as drinking water from groundwater, water regulation, groundwater purification, carrying capacity and temperature buffering.
Ecosystem services for soil and groundwater management
In the Netherlands, the ecosystem services concept has been taken up by policy makers as basis for sustainable use of subsurface resources. The ambition for groundwater is to exploit multiple ecosystem services without unacceptable impact on other ecosystem services and to sustain groundwater quality and quantity to ensure the provision of ecosystem services in the long term. Besides, a new policy will be developed for spatial planning of the subsurface, that addresses (current and potential) conflicts in the subsurface, e.g. related to aquifer thermal energy storage, shale gas extraction, storage of substances, groundwater extraction for different purposes, etc.
The mapping of ecosystem services in the context of the National Ecosystem Assessments and the European Biodiversity Strategy can support these new policy developments and decision making by providing comprehensive (spatial and temporal) information about ecosystem services related to subsurface ecosystems.
The role of the subsurface in ecosystem services maps
The subsurface system is an important part of our natural capital that provides many ecosystem services to society. The first edition of the Netherlands Atlas of Natural Capital therefore will include about 40 maps with spatial explicit information on:
• the potential of ecosystems to deliver soil and groundwater related services;
• trends, opportunities and threats to these ecosystem services
• the use of these services.
An example of an ecosystem service map is given below.
We will demonstrate maps of soil and groundwater related ecosystem services, share lessons learned from the development of these maps, and we will discuss the importance of the subsurface environment for ecosystem services and possible future directions to include environmental data in National Ecosystem Assessments at different spatial and temporal scales.
The main purpose of the study is to evaluate wider environmental impacts, i.e. impacts other than those directly related to land use (both on- and off-site), of brownfield (BF) development by applying and then evaluating and applying the Life Cycle Thinking (LCT) approach to three real-world case studies. LCT seeks to identify possible improvements to goods and services in the form of lower environmental impacts including reduced use of resources across all life cycle stages. In the case of Brownfield development this includes the remediation, construction, future use and decommissioning stages.
In many cities there are abandoned or under-used industrial areas, which were developed previously and can have residual in-situ contamination from earlier activities. These areas can be remodelled in order to satisfy the increasing demand for new urbanized areas with different purposes, including residential use, infrastructure or green areas.
Urban planning activities have associated environmental impacts over a long time period, as the result of planning conditions the behaviour of cities over several years. From a sustainability point of view, considering all life cycle stages, including early project stages, is desirable. Holistic approaches supported by comprehensive tools are needed to guarantee this view.
Existing literature suggests that the environmental impacts of brownfields development projects are not considered in a holistic manner. Usually only specific aspects, such as selected impacts from remediation activities or construction activities, are assessed. Therefore, applying the Life Cycle Assessment (LCA) approach to brownfield developments is seen as a good opportunity to assess the overall environmental ‘profile’ of such developments and identify possible improvements in their management.
Recently EEA has led a study to explore the feasibility of applying the LCA approach to reusing brownfields as part of urban planning. Three case studies were analysed including two different brownfields and a greenfield (non-urbanised area). The study includes all life cycle stages and the associated impacts: i) primary impacts, associated with the site status, including soil and groundwater contamination; ii) secondary impacts, related to the development stage (soil investigation, soil remediation, demolition of existing buildings, levelling works, infrastrucutres construction and construction of new buildings); and iii) tertiary impacts, associated with the use of the site after development.
Outcomes from the study show potential to succesfully apply life cycle thinking approaches to brownfields and urban (re)development projects. The selection of a representative funcional unit (depending on the planned use of the remodelled area, the surface, the built surface, or the number of residents/users) proved to be a key parameter affecting the results. The findings showthat, for the three cases, the most relevant life stages in terms of environmental impacts are the use stage (with a selected duration up to 20 years), as well as the development stage with important contributions from the construction of new buildings and construction works.
Management of the subsurface by spatial planning
It is a worldwide development that in intensively used areas, a growing number of solutions for the densely used surface is found in the subsurface. In the Netherlands it is growing accustomed to build parking lots in city centres in the subsurface, build railway’s and highways underneath nature reserves and make use of the possibility for ATES or geothermal energy. In addition to these rather new developments, we also have mining activities and drinking water supplies in the subsurface.
With the increasing use of the subsurface, conflicts can occur that cannot be solved by local governments alone.
The Dutch Cabinet assigned an integrating role to the subsurface in policymaking. Their ambition is a broad policy document for a sustainable and efficient use of the subsurface, including a spatial plan for the subsurface. The spatial plan should cover all the central government aims to secure energy supply and drinking water supply.
The Netherlands is in the process of making an Environmental Impact Assessment (EIA) as a preparation for a spatial plan for subsurface use of national importance. In fact two EIA’s are made. One especially for shale gas and another one for several activities in the deep subsurface like large groundwater extraction for drinking water supply or industrial use, gas extraction, salt extraction, geothermal energy, and storing gas or other products in the subsurface.
In the process of making the EIA, a broad policy document is written in which a system is developed for weighing different interest in the subsurface. Central government wants to come up with a democratic accounted decision making system that will give clarity in how decisions are made.
Important questions that will be answered in the presentation are:
What scenario's are accounted for in the EIA, which alternatives are described and how specific will this national plan for the subsurface become. In addition I will explain the balancing of different interests and how are local governments involved in this decision making process?
The innovative MIP-IN device combines (1) detection of pollutants by for instance a membrane interface probe (MIP) and (2) a simultaneous correlated injection (IN) during direct push of the device using a Geoprobe®. The MIP-IN device is the basis for a new detection-injection technology with the main advantage of the nearly simultaneous coupling of detection of pollutants at a certain depth and injection of a suitable amount of reactive agent at that precise spot. In this way, the injected reagent is more targeted towards the real location of the pollution with reduced remediation time and cost.
The MIP-IN concept was developed within the FP7 UPSOIL project (EU GA 226956). A first prototype version of the device was used for injection of guar gum stabilized zerovalent iron in a contaminated subsurface as part of the FP7 AQUAREHAB project (EU GA 226565). MIP-logs showed that chlorinated pollutants were present in the subsurface at distinct depths between 2 and 12 meter below ground surface, but the exact depths altered from spot to spot. The MIP-IN injection approach was used to inject guar gum stabilised micro-scale zerovalent iron slurry in a challenging sandy subsurface using high injection pressures, high flow and relatively low injection volumes. After the injection, undisturbed soil samples were taken to verify the distribution of the injected material. It was shown that the MIP-IN device was able to inject guar gum stabililized zerovalent iron at depths where CAHs were detected, and that the MIP-IN approach has potential. To deliver the reagent at the injection depth, the targeted radius of influence of 0.5 m was found suitable. Automatic logging of injection parameters (volumes, times, depths, ..), not yet available for the used prototype MIP-IN version, was identified as a crucial aspect for further improvement of the device and the injection.
Since end 2013, the MIP-IN device is being further developed and tested within the MIP-IN EUROSTAR-project (E!8246) where VITO (Belgium), Ejlskov (Denmark), Ecorem/ABO (Belgium) and Dekonta (Czech Republic) joined forces. The main goals of the MIP-IN EUROSTARS project are to (1) improve the MIP-IN device, (2) validate the MIP-IN device in relevant environments and define boundary conditions, and (3) develop an innovative MIP-IN based remediation strategy closely linked with site investigation, based on 3-D modelling of MIP data.
A set of different MIP-IN-probes has been developed and are being tested in the field in different geologies and for different reagent types. At a Danish site (clay) BOS200 has been injected at an oil contaminated site, while nanoscale ZVI was injected at a Czech site where chlorinated compounds were present. Early 2015, a field test in Belgium is scheduled, where EHC-L and guar gum stabilized micro-scale iron will be injected in a sandy soil using the MIP-IN device. An overview of the results of these field tests will be presented, with focus on the functioning of the MIP-IN device and its added value. Further, the potential of the MIP-IN based remediation strategy will be explained and illustrated with an example.
Since the 1980s, several subsurface investigations conducted to evaluate impacts at an industrial facility in California have identified volatile organic compounds (VOCs) in shallow soil and soil gas underlying the site. VOCs have also been identified in groundwater encountered at approximately 180 feet (ft) below ground surface (bgs). However, the assemblage of detected VOCs in the shallow horizons (soil/soil gas) is significantly different than that observed in the deeper groundwater. Shallow VOC impacts (i.e., <~55 ft) are predominantly tetrachloroethene (PCE) with minor amounts of benzene, toluene, ethylbenzene, and xylenes (BTEX), carbon tetrachloride, other substituted benzenes, and a notable near absence of trichloroethene (TCE). The deeper groundwater is characterized by a predominantly TCE signature, with very low PCE concentrations. Collectively, the site data suggest that PCE impacts from historic site uses were limited to shallow depths, and the observed TCE in groundwater beneath the site had likely migrated from an upgradient location off-site. However, additional lines of evidence were needed to confirm this conceptual model, support traditional site assessment data, and to direct the path of future investigation and/or remediation efforts.
ENVIRON conducted an investigation to evaluate the vertical distribution of VOCs in soil gas beneath areas of the site where elevated PCE concentrations had been identified in previous testing. Borings were advanced to approximately 100 ft bgs, and nested soil vapor probes were installed. Soil vapor samples were collected and analyzed for VOCs including PCE, TCE, cis-1,2-dichloroethene, trans-1,2-dichloroethene, and vinyl chloride. Based on the bulk compositional analyses, select soil vapor samples were collected for compound specific isotope analysis (CSIA) of carbon and chlorine. In addition, groundwater samples from monitoring wells at the site were submitted for CSIA (carbon, chlorine).
ENVIRON used the CSIA and bulk composition results in soil gas and groundwater, coupled with fate and transport modeling for the site to evaluate and ultimately confirm the original conceptual model – that groundwater impacts beneath the site originates from an upgradient source. Moreover, the data suggest that the shallow VOCs (predominantly PCE) in soil gas have not undergone reductive dechlorination during transport, further evidence that a putative source for the TCE in groundwater does not exist on-site. The isotopic data from soil vapor and groundwater, combined with traditional site characterization data helped to validate and refine the conceptual site model. New CSIA results from additional vapor probes installed in early 2015 will be included that provide further resolution of the isotopic conditions at the site.
Groundwater discharge can be an important contaminant source to surface water bodies and must be addressed when responding to legislation like the EU Water Framework Directive, which aims to protect and restore surface water bodies. Since contaminated sites are a major source of contaminants in groundwater resources it is important to evaluate the risks posed by them to streams. Such risk assessments are the basis the selection of appropriate and cost-effective remediation actions. This is a challenge because little is known about how contaminant discharge to stream varies because of stream meandering and changes in the water levels in streams and in aquifers.
This study aimed to develop a model of groundwater discharge to streams that incorporates the stream morphology and the time varying water levels in streams and in aquifers. The model was applied in order to determine the likely location of groundwater discharge in streams, and determine the origin of that groundwater. The models also showed that time-varying stream water level and groundwater head affect the discharge. The model was developed for a field site at Grindsted stream, a study site located in Denmark. The study aimed to use the model to analyze groundwater discharge measurements obtained at the field site. The work provided new insight on groundwater/surface water interaction and the interpretation of field data.
The project successfully developed a three-dimensional COMSOL Multiphysics model for groundwater discharging into Grindsted stream. The model accounts for the geometry of the stream and the geological heterogeneity of the aquifer. In addition, it includes the time variability in stream and aquifer water levels.
The study site was characterized by an extensive field campaign. The model was used to design the field monitoring and then, once data was collected, was compared with Point Velocity Probe and stream temperature measurements which provided data on the location, magnitude and direction of groundwater discharge to the stream. The results were also compared with time series of head data at monitoring wells located next to the stream. The model was shown to reproduce field data very well, leading to confidence in results.
It was observed that the discharge into the stream is highly dependent on the gradient between the stream and the aquifer. Thus, temporal variability in the discharge is correlated to changes over time of the gradient. In addition, the geological heterogeneity of the aquifer underneath the stream was shown to affect the groundwater flow, the discharge into the stream and the provenience of the discharged water.
This study showed that the presence of meanders had high impacts on the discharge and on the groundwater flow in proximity of the stream. The results indicated that the upper part of the aquifer mostly discharges in the outward pointing meanders, while groundwater from the lower part enters the stream from the opposite side. Furthermore, the groundwater discharge velocity is higher in the outer part of the meander bends. The observation was supported by contaminant concentration measurements in the groundwater collected nearby the stream. This suggested that groundwater discharge through a stream bank does not necessarily originate from the same side of the stream. Stream monitoring data should therefore be carefully interpreted in order to avoid misunderstandings based on the assumption that groundwater originates from an area on the same side as a given stream bank.
The results of this study showed that groundwater discharge to streams varied greatly with location, depth and time. Furthermore, the stream morphology and the geological heterogeneity has a great impact on stream-aquifer interaction. This study also indicated that mathematical models are very useful for interpreting field data and for designing monitoring campaigns. The joint application of field investigations and modelling tools can be used for better understanding the contaminant mass discharge into streams. This may improve the risk assessment and reduce the costs for remediation and monitoring, in order to fulfill the requirements in the EU Water Framework Directive.
Introduction: Water quality in rivers typically depends on the degree of urbanization or the population density in a catchment. Transport of many pollutants in rivers is coupled to transport of suspended particles, potentially dominated by storm water overflows and mobilization of legacy contamination of sediments. Concentration of these pollutants strongly sorbed to suspended particles cannot be diluted by water directly, but depends on the mixture of “polluted” urban and “clean” background particles (Schwientek et al. 2013). In the current study, the total concentration of polycyclic aromatic hydrocarbons (PAHs), the amount of total suspended solids (TSS) and turbidity were measured on a monthly basis in water samples from 5 neighbouring catchments with contrasting land use in Southwest Germany and in 3 sub-catchments of the Bode River in Eastern Germany over up to 1.5 years. In addition, single flood events with large changes in turbidity were sampled at high temporal resolution. Suspended particles representing different time periods of pronounced events were also characterized towards type and geochemistry (total organic carbon and carbonate content, grain size distributions). Using on-line monitoring of turbidity (by optical backscattering sensors) mass flow rates of PAH over time were calculated.
Results and discussion: Linear correlations of turbidity and TSS where obtained over all catchments investigated and over an extended turbidity range (up to 2000 NTU for the flood samples). Linear correlations were also obtained for the total amount of PAH and suspended sediment concentrations even for very high turbidity or TSS values (> 2000 NTU or mg l-1, respectively). From the linear regressions concentrations of PAHs on suspended particles were obtained – which varied by catchment. The values comprise a robust measure of the average sediment quality in a river network or catchment and may be correlated to the degree of urbanization represented by the number of inhabitants per total flux of suspended particles. PAH concentrations on suspended particles were stable over a large turbidity range (up to 2000 NTU) confirmed by samples taken during flood events. No pronounced effects due to changing particle size or origin have been observed for the catchments investigated (< 150 squared km; Rügner et al., 2014). Results of on-line turbidity monitoring showed that high turbidity/discharge events account for major proportion of pollutant fluxes (this study: 90% PAH flux > 90 NTU; events representing only 2.5 % of the observed time period).
Conclusions: Turbidity may be used as proxy for the total concentration of suspended solids (TSS) and particle-bound pollutants in river water. From regressions of total PAH vs. TSS (or turbidity) concentrations on suspended sediments (Csus) may be calculated. For calculation in principle a single event is sufficient. Contamination of suspended particles depends on urban pressure per total suspended particle flux. The findings are promising for other particle-bound contaminant fluxes (PCBs, phosphorus, and several heavy metals, etc.).
References:
Schwientek M, Rügner H, Beckingham B, Kuch B, Grathwohl P. 2013. Integrated monitoring of transport of persistent organic pollutants in contrasting catchments. Environ Poll 172:155-162.
Rügner H, Schwientek M, Egner M, Grathwohl P. 2014. Monitoring of event-based mobilization of hydrophobic pollutants in rivers: Calibration of turbidity as a proxy for particle facilitated transport in field and laboratory. Sci Tot Environ 490: 191-198.
Acknowledgement:
The authors thank the Ministry of Science, Research and Arts of Baden-Württemberg (AZ Zu 33-721.3-2) and the Helmholtz Centre for Environmental Research - UFZ, Leipzig. The study was also supported by the European Communities 7th Framework Programme under Grant Agreement no 603629-ENV-2013-6.2.1-GLOBAQUA.
Plumes of dissolved contaminants may be widely distributed in the saturated zone, i.e. to great depths and over large areas. Also the concentration levels of contaminants in the plume generally are much lower than the concentrations found in the hotspot area. Characterization and delineation of contaminant plumes therefore typically require many investigation points at great depths. Often the delineation of a contaminant plume is conducted using traditional drilling techniques and installation of screened wells. However, this method is both time-consuming and resource-intensive and only a limited number of discrete depths can be screened in each well. Furhermore, screen depths are often chosen based on expected flow and contaminant distribution patterns in the saturated zone, rather than on detailed hydrogeological data and vertical contaminant distribution.
On behalf of The Capital Region of Denmark, Department of Regional Development, and in cooperation with experts from Geoprobe Systems (US), NIRAS A/S (DK) has tested a novel tool, Low-Level MIHPT (LL-MIHPT), for delineation and characterization of contaminant plumes in groundwater. LL-MIHPT is based on the existing high resolution direct push investigation tools MIP and HPT developed by Geoprobe Systems. The HPT probe (Hydraulic Profiling Tool) is used to continuously map the hydrogeological conditions (permeability), while the MIP probe is used to continuously map VOC contamination in soil and groundwater. The MIHPT system is a combination of the MIP and HPT systems and has proved to be very efficient for field investigations in hotspots and areas with high contaminant levels. However, the detection limits of the standard MIHPT system are too high for delineation of contaminant plumes where the concentration levels are significantly lower than in the source zones. The Low-Level MIHPT system is developed with the objective to detect contamination at low concentrations and thus provides a means for conducting more time efficient and cost-effective delineation of contaminant plumes in unconsolidated saturated formations.
The LL-MIHPT systems has been tested at two sites located in the towns of Farum and Slangerup in Denmark as part of ongoing field investigations at the two sites.
The purpose of this project was to test the LL-MIHPT technique for delineation of contaminant plumes in groundwater at two sites with different geological formations; sandy and clayey, respectively. The objectives have thus been to determine at which concentration level the LL-MIHPT system could detect the site specific contaminants and to investigate the correlation between observed LL-MIHPT responses and results from analysed water samples from targeted depths.
9 LL-MIHPT logs to 20-25 meters below surface have been carried out. At each log water samples were collected at specific depths with the GeoProbe for verification of the observed responses from the LL-MIHPT and for correlation of contamination levels. For further correlation of the LL-MIHPT data core samples were collected at three locations.
The results from the field tests show that it is possible with the LL-MIHPT to track relatively low concentrations of chlorinated solvents and BTEX’s in the saturated zone. Hence, for chlorinated solvents a detection limit in the order of 10 ug/L can be expected. For comparison the detection limit for chlorinated solvents with the standard MIP system is in the order of 1-10 mg/L.
Based on the results and experiences obtained from the field tests the new LL-MIHPT system shows good promise for delineation of contaminant plumes in the saturated zone with simultaneous retrieval of hydrostratigraphic data from the saturated zone. Thus, LL-MIHPT logs followed by depth specific groundwater sampling with the GeoProbe system is considered to be an optimal set-up for delineation and characterization of contaminant plumes in saturated zones in unconsolidated geological formations.
The field tests were conducted and evaluated in the fall of 2013 and spring of 2014. Since then NIRAS A/S has used the LL-MIHPT system at field investigations at several other sites. Thus, the presentation will include results from the field tests in Farum and Slangerup complemented with the most recent data.
The list of priority substances for which environmental quality standards were set in 2008 has been recently modified, increasing the number of substances or groups of substances from 33 to 45 (DIRECTIVE 2013/39/EU). New monitoring methods as passive sampling and other instruments have a promising future application for detection and quantification of micropollutants not yet regulated. Scientific community and water operators go one step forward finding innovative solutions for the elimination of these undesirable substances in water depuration and purification processes.
In this context, the 7th Framework Programme European co-funded DEMEAU project means a unique opportunity to demonstrate how conventional and alternative water treatment processes can deal with the emerging pollutants elimination in drinking water processes and anthropogenic-impacted environments. Managed Aquifer Recharge (MAR) is one of the four promising technologies evaluated in DEMEAU. First output available include a complete European MAR catalogue with the characterisation of more than 300 MAR sites. The catalogue shows how MAR is widely spread in 23 European countries.
The demonstrative phase of the project includes the analysis of selected emerging pollutants in a simulated MAR system fed with reclaimed water. The selection of the target compounds has been made according to the following criteria: (i) presence in wastewater and drinking water supplies, (ii) environmental relevance; (iii) chemical and physical properties and (iv) existence of analytical method/s for their quantification.
The objective of this work is to present the results of the demonstration phase of DEMEAU project concerning the simulation of a MAR system using reclaimed water in aerobic and anaerobic conditions. Therefore, the evaluation of the elimination potential of emerging compounds by Soil Aquifer Treatment (SAT) is presented. Aerobic and anaerobic conditions have been selected because they are known be significant for emerging pollutants abatement in MAR facilities (Heberer et al. 2008).
The Waste Water Treatment Plant (WWTP) of El Prat del Llobregat has been selected for the operation of two experimental columns simulating the process of aquifer recharge with (i) direct water from the secondary treatment of the plant (anaerobic conditions) and (ii) water after 10-15 days aeration (aerobic conditions). Water injected from the secondary effluent has a high concentration in ammonia and a low dissolved oxygen content.
Columns are made of stainless steel (1.50 meters high and 0.50 meters of inner diameter) and have been operated at a residence time of about 2 months. The filling material is constituted by homogeneous sand grains enriched with 1% of organic matter, simulating the natural conditions of an alluvial aquifer (Barbieri et al. 2011). Emerging pollutants are naturally present in the effluent of the secondary treatment of the WWTP selected at different concentrations in the range of micrograms/L and nanograms/L (see Table 1, Teijon et al., 2010). pH, redox potential, dissolved oxygen, total organic carbon, turbidity and major ions (NO3-, NO2-, NH4+, SO42-) have been analysed regularly in recharge water and output water to monitor MAR process response. The analysis of the behaviour of 11 selected emerging compounds along the experiment has been also carried out.
The results shown geochemical changes occurring along the recharge period and their relation with emerging micropollutants removal. Results obtained in the experimental phase have been used to feed a toolbox to help new MAR facilities implement and operate successfully under different field conditions. Specifically in Spain, results are useful for the start-up of the deep injection system located in the area of the Vall d’Uxó (Castellon), in the Mediterranean coast.
References
Barbieri, M., Carrera, J., Sanchez-Vila, X., Ayora, C., Cama J., Köck-Schulmeyer, M., López de Alda, M., Barceló, D., Tobella Brunet, J., Hernández García, M (2011). Microcosm experiments to control anaerobic redox conditions when studying the fate of organic micropollutants in aquifer material. Journal of Contaminant Hydrology 126 (2011) 330–345.
DIRECTIVE 2013/39/EU of the European Parliament and of the Council of 12 August 2013 amending Directives 2000/60/EC and 2008/105/EC as regards priority substances in the field of water policy. Official Journal of the European Union. 24.8.2013.
Heberer, T.; Massmann, G.; Franck, B.; Taute, T. and Dünnbier, U. (2008). Behaviour and redox sensitivity of antimicrobial residues during bank filtration. Chemosphere 73, 451–460.
Teijon, G., Candela, L., Tamoh, K., Molina-Díaz, A., Fernández-Alba, A. R. (2010). Occurrence of emerging contaminants, priority substances (2008/105/CE) and heavy metals in treated wastewater and Groundwater at Depurbaix facility (Barcelona, Spain). Science of the Total Environment 408 (2010) 3584-3595.
1. Introduction
Contamination of drinking water resources is becoming a threat that is particularly widespread. Nowadays even in European countries clean drinking water is at risk. Pharmaceuticals, pesticides and other micropollutants are emerging substances in surface and groundwater causing contamination of drinking water resources and ultimately to closing down groundwater abstraction wells.
2. Background
Pesticides and other micropollutants in groundwater and surface water are more and more present in very low concentrations, in the nanogram to microgram per litre range. Concentrations already exceed the EU limit value for pesticides (or other micropollutants) in drinking water recourses. Closure of the groundwater abstraction wells or the entailing treatment is costly. It is important to find a sustainable and cost-effective remediation technique since it remains unknown if there are long term cumulative dose-additive or synergistic effects of low concentrations of substances occurring as a mixture. Knowledge of degradation processes at such low concentrations is limited and novel approaches are needed to develop biological treatment technologies that are efficient at these low concentrations.
BIOTREAT is a European project in which urgently needed sustainable biotechnologies are developed for remediation of drinking water resources contaminated with micropollutants such as pesticides and pharmaceuticals and their metabolites.
The basis of the technologies is bioaugmentation, which in this case is the introduction of specific degrading microorganisms or microbial consortia into existing sand filters at waterworks or mobile filters placed close to the (groundwater) abstraction well.
The compound BAM (2,6 Dichlorobenzamide) has been chosen as model compound for metabolic biological degradation. BAM is a metabolite of the broadly used herbicide dichlorobenzonitrile or dichlobenil. The bacterium Aminobacter sp. MSH1 is found to be capable to mineralize BAM.
A strategy using metabolic degradation pathways was used to target water-pollution cases where metabolically degrading bacteria are available. In order to simulate drinking water production at waterworks we have up scaled the lab-scale batch experiments to a sand filter column experiment in our lab and finally to a medium scale sand filter column that is used as experimental column at a drinking water well. The BAM mineralizing bacterium was found capable to degrade the metabolite in batch culture and sandfilter column experiments at low concentrations. Pilot scale sand columns have been designed based on these results. A Life Cycle Analyses (LCA) and a cost benefit analyses (CBA) have been performed in order to gain insight in the sustainability and cost effectiveness of the developed technologies. Based on the technical results, the LCA and the CBA actions plans for implementation of the developed technologies could be made.
3. Biotreat partners
GEUS, DTU, University Leuven, EAWAG, University Gent, Bundesanstalt für Gewässerkunde, Avecom, LCA 2.0, Bioclear
After more than 20 years´ work and an expenditure of some 160 million euros the remediation project regarding the site of a former explosives production plant is nearing completion. During the remediation, thanks to a close cooperation with all relevant stakeholders during planning and implementation, the drinking water production was able to be continued without any interruption. The remediation will ensure a long-term future utilization of the site for housing and industrial and commercial purposes, as well as drinking water production.
The production of explosives from 1939 to 1945 and the subsequent improper closedown of the plant after the end of the war caused that considerable amounts of contaminants (in particular nitroaromatic compounds e.g. TNT) were released into the environment. Despite this pollution, the location has evolved into a place to live and work, which is important for the region. Today some 8,000 people live and work on the former site. The domestic drinking water and industrial water supply has been covered by the Stadtallendorf waterworks with an annual resource of approx. 10 million m³. All activities made use of the existing infrastructure of the former explosives production plant (buildings, roads, pipes, wells and treatment facilities).
In the 1980s investigations carried out at the site made it clear that the soil and groundwater pollution was a serious threat, as far as the further utilization and the environment in general was concerned. This caused a major uncertainty among the local population, going as far as debates as to whether the location should be completely abandoned.
In view of the intensive utilization of the site a risk management concept for the remediation was developed in consultation with all stakeholders. This was devised to safeguard the various types of land use of the site on a long-term and sustainable basis, both during and after the remediation, and ensure a relevant reduction of contaminants. The safety of the supply of drinking water was a key target of the remediation work which, once the contamination of soil and groundwater had been established, became the main priority.
Apart from the utilization-based soil remediation, which in the hot spots (as a general rule up to a depth of 3 metres) involved the removal of approx. 150 tonnes of nitroaromatic compounds, the concept also provided for hydraulic measures. Since 1995 this has prevented contaminated groundwater from flowing into the drinking water wells. The water extracted (approx. 450,000 m³/a) is processed in a two-line water treatment system (activated carbon). The output volume of the extraction and the pumping rates of the drinking water production are synchronized.
The hydraulic measures undergo meticulous monitoring measures. All stakeholders have access to the data collected via an internet-based information system. Within a project of the German KORA research network a model has been developed to assess the impact of interventions in the hydraulic system.
The remediation of the site will not be finalized with the completion of the soil remediation. The remaining contaminants in the soil make it necessary for the hydraulic measures to continue in operation and that there is a controlled approach dealing with the soil in the course of any building projects.
Therefore, the remediation phase will be followed by an indefinite period after-care phase which will involve follow-up work regarding the soil, hydraulic measures, contract and project management plus data and knowledge management.
Alongside the technical measures, hydro-geological and geological bases and natural attenuation processes, as well as operational experience, the paper addresses in particular the cooperative process of developing targets and measures with the various stakeholders involved, which of course includes the necessary communication throughout the entire process. The requirements for long-term data and knowledge management will also be illustrated, and the tools used outlined.
Perfluorinated compounds (PFCs) are a large class of synthetic fluorine-containing chemicals that is receiving increased attention by government agencies and land owners in the United States (U.S.). The structure of PFCs consists of a fluorinated carbon chain, with a varying number of carbon atoms, and a charged functional group such as a sulfonic or carboxylic acid. PFCs historically have been used in a variety of industrial and consumer applications and products, including coatings, aviation hydraulic fluids, fire-fighting foams; household care products (including paints, adhesives, waxes and polishes); water, stain, and grease repellant coatings on textiles, leather, and carpet. The two PFCs with the largest historical production and use in the U.S. are perfluoroctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). Production of PFOS by its largest U.S. manufacturer in the ended in 2002, and worldwide production of PFOA and analogous PFCs currently is being phased out.
PFCs have extremely high structural high stability due to the strength of their carbon-fluorine bonds. This attribute causes PFCs to be chemically inert, maintain stability at high temperature, resist degradation in the environment, have low volatility, and bioaccumulate in animals. In addition, PFCs tend to have a much higher aqueous solubility and low sorption affinity compared to highly chlorinated pollutants of concern, such as polychlorinated biphenyls and dioxins. The U.S. Environmental Protection Agency (EPA) Science Advisory Board has characterized PFOA as a likely human carcinogen; however, the U.S. EPA has not yet issued regulatory criteria for PFCs in drinking water. Instead, U.S. EPA has issued Provisional Health Advisory (PHA levels), which are drinking water concentrations that are not known to cause adverse health effects from short-term consumption. The U.S. EPA PHA levels for PFOA and PFOS are 0.4 ug/L, and 0.2 ug/L, respectively. Certain State government agencies in the U.S. have specified drinking water criteria that are different than the U.S EPA PHA levels; Minnesota, for example, has set health risk limit levels for PFOA and PFOS of 0.3 ug/L each, and New Jersey has established a preliminary drinking water guidance value for PFOA of 0.04 ug/L.
Understanding of the environmental occurrence and distribution of PFCs in the U.S. is still in its infancy, similar to understanding of the occurrence of perchlorate and 1,4-dioxane in the U.S. 15 years ago. Because the analytical methods for quantifying PFCs in groundwater and drinking water samples, which typically involve high pressure liquid chromatography in combination with mass spectrometry (HPLC/MS), are not routinely used in the analysis of aqueous samples, PFCs in environmental media have gone undetected in a majority of cases. However, a growing body of data suggest that, the more that proper HPLC/MS methods are used to screen environmental samples for PFCs, the more that they are detected at U.S. sites. For example, detection of PFCs in soil and groundwater at fire-fighting training areas in the U.S. has increased significantly. The U.S. Department of Defense (DoD) has estimated that up to 600 DoD sites have been used for fire-fighting or crash training and therefore are potential candidates for PFC contamination.
Due to the stability of their carbon-fluorine bonds, PFCs resist many conventional in situ treatment technologies. Ex situ treatment options including reverse osmosis and filtration through granular activated carbon have been shown to treat PFOS and PFOA successfully. Results of recent research suggest that less expensive treatment alternatives for treatment of PFOS and PFOA in groundwater are on the horizon, including ultrasonic irradiation (sonochemical degradation), and in situ chemical oxidation using heat-activated persulfate and permanganate. Clearly, there is need for private and public sector stakeholders around the world to develop and commercialize more cost-effective methods for treating PFOA and PFOS.
This presentation will provide a state-of-the-science overview of historical usage, toxicity, environmental occurrence, environmental fate and transport, and treatment methods for PFCs, as well as current U.S. EPA and State government regulations regarding PFCs.
Bottom-up regional initiatives to tighten up the generic pesticides rules and regulations in the Netherlands
Cors van den Brink@ (RHDHV), Carolien Steinweg (RHDHV) and Anton Dries (Province of Drenthe)
@corresponding author: cors.van.den.brink@rhdhv.com
Abstract
The presence of pesticides in groundwater and surface water in the Northern part of the Netherlands provides a threat for the sustainable drinking water supply. In addition the objectives of the Water Framework Directive may not be met in time. During the last decades various projects have been defined by several stakeholders to study this problem. And also to reduce the risk of pesticides by informing land-users and citizens by (financially) supporting land use management aiming a reduction of the risks by the use of pesticides. However, a comprehensive overview of the presence of pesticides in groundwater and surface water carried out in 2011 showed that WFD-limits were exceeded in approximately 28% of the monitoring wells. To be able to identify and implement effective measures with the appropriate stakeholders, the use and risks of the pesticides were established in the Northern part of the Netherlands.
The analysis of the use and risks of pesticides consists of i) analysis of the actual concentrations of pesticides in groundwater and surface water measured with the regular monitoring networks of the provinces and water boards ii) analysis of the spatial distribution of pesticides in groundwater and surface water, and iii) evaluation of the success factors of initiatives in and outside the region.
The evaluation of the monitoring sites of groundwater and surface water showed that pesticides provide a risk for the groundwater quality in the sandy areas. In areas with more heavy soil types such as clay and peat, the risks of the use of pesticides shift from groundwater towards surface water.
The spatial distributions were calculated based on agricultural and non-agricultural pesticide application reported by regional experts in 1997 and 2010, combined with the land use, soil type, and pesticide characteristics. The measured and calculated risks were corresponding for 70% of the monitoring sites. From the distributions of 1997 and 2010 it was concluded that the risk has been reduced with 80 – 90% for both agricultural and non-agricultural use of pesticides. Nonetheless, the risks are still too high in specific areas and for specific crops. The stakeholders accepted the pesticide-application figures because these figures were provided by regional experts. They also concluded that the instrument could be used to define and evaluate scenario’s aiming at a reduction of the risk of pesticides in the second step of the study.
The second step consisted of i) the selection of top-10 pesticides in groundwater and surface water, ii) the set-up of an analysis framework to define the major focus on reducing risks for each top-10 pesticide, and iii) identification of effective measures together with the stakeholders.
This study shows that combining various points of view, data sources, and stakeholders together with administrations made it possible to make a comprehensive overview of the use and risk of pesticides in the Northern part of the Netherlands. The role and knowledge of regional experts was important for the acceptance of the results calculated with these data. Tools used to structure, quantify and visualise the relevant data and collective understanding were necessary to provide an informed basis for the dialogue, exploration and decision-making in both phases of the study. However, this analysis also showed that even the use of approved pesticides in an approved way and moment of application will result in exceedance of the WFD-limits.
In addition, a detailed analysis of the top-10 pesticides showed, that the risk of the pesticides measured in groundwater and surface water could not be explained and the risks of environmental friendly alternatives were in the same order as the top-10 pesticides. The main results of the study showed that:
- A comprehensive overview of the use and risks of pesticides is carried out and accepted by all stakeholders involved;
- Regional measures will not be effective within the generic rules and regulation because:
o Actual risks result from approved pesticides applied in an appropriate way;
o Adequate instruments to identify and stimulate environmental friendly alternatives are lacking
The tightening up of the generic rules and regulations is therefore the only feasible way to reduce the risks of pesticides. Two tracks have been developed i) based on the results of the analysis, a position paper signed by the authorities of the Northern part of the Netherlands has been sent to the Dutch ministry of Infrastructure and Environment and ii) the monitoring data are used to evaluate the official national approval procedure by the Dutch Board for the Authorisation of Plant Protection Products and Biocides.
As result of the position paper, the issue is ‘on the agenda’ and is discussed in the appropriate fora. In addition, the evaluation of the national approval procedure has resulted in an ongoing and constructive discussion with the Board for the Authorisation of Plant Protection Products and Biocides which might result in changes in the authorisation of riskful pesticides.