1C.1 - Bio-remediation
1C.2 - Chemical oxidation
1C.3 - Hydrocarbons
1C.4 - Heavy metals
Laboratory and field data are presented underpinning a new technology development for achieving very fast risk reduction in the groundwater pathway (days) and for securing contaminant destruction to stringent targets (low part per billion range) using a passive, low-energy approach. The technology is particularly suited to the management of large, diffuse spreading plumes, and for deep, low concentration plumes in complex geologies. The technology requires no energy or intervention post application, and is expected to remain functional for decades.
The technical innovation allows for wide dispersion of a sorptive medium in the aqueous subsurface. The medium has a dual function; it sorbs contaminants, quickly removing them from the mobile phase, and provides a high surface area matrix favorable for microbial colonization and growth. Contaminant availability within a risk pathway is therefore reduced while at the same time contaminant destruction is accelerated.
Upon reagent injection, target contaminants partition out of the aqueous phase and into the reagent matrix, thereby removing mobile contaminants from the immediate risk pathway. Concentration of the contaminants in this manner, in a matrix conducive to degrader colonization and activity, results in a direct increase in the overall instantaneous rate of contaminant destruction, given the quasi first-order biodegradation kinetics characteristic of environmental systems. This phenomenon can be especially important at low contaminant concentrations, which may otherwise prove insufficient to support appreciable growth and activity of a degrading microflora. When necessary, the medium can be applied in combination with compatible electron donors / acceptors.
The technology can be employed to inhibit spreading of contaminant plumes, to protect sensitive receptors, or to prevent contaminant migration across property boundaries. The technology is also postulated an effective tool for control and treatment of groundwater contamination associated with low-permeability porous formations and matrix back-diffusion, promoting diffusion out of the immobile porosity while preventing groundwater impact.
Field studies confirm wide-area dispersion, with order of magnitude (>90%) dissolved-phase concentration reductions secured at the test sites post-application sampling, increasing to two orders of magnitude (>99%) within two months for both chlorinated solvent and hydrocarbon species alike. Laboratory and microbial quantitative array field data provide confirmation of post-sorption degradation enhancement, with laboratory studies describing a significant increase in the rate of contaminant destruction in biotic matrix systems compared to abiotic matrix and biotic non-matrix controls.
Biofuels, such as biodiesel, are increasingly being used as fossil fuel replacers in transportation due to issues associated with climate change and energy security. Fossil diesel is a complex mixture of hydrocarbons, and includes aromatics such as toluene. As it is with any other fuel, inadvertent releases and transportation accidents have lead to soil and groundwater contamination.
Although biodiesel is increasingly being used, little is known about its fate under different redox conditions, such as nitrate-reducing conditions, and the impact on microbial diversity. In addition, the presence of biodiesel may negatively impact toluene biodegradation; however, limited information is available concerning nitrate-reducing conditions. Therefore, the aim of this study was to examine the fate of biodiesel under nitrate reducing conditions and its impact on both microbial diversity and toluene biodegradation.
Microcosms were setup using approximately 5 g of sediment collected from two contaminated sites with 100 mL of anaerobic media in 125-mL serum bottles. The initial amount of nitrate present was 2 g/L. Microcosms were purged for 15 minutes with nitrogen gas and sealed with Teflon-lined septa and aluminum crimp caps. Afterwards, the batch reactors were incubated statically, upside down, in the dark, at 25 °C. Tests included: biodiesel alone, biodiesel + toluene, and ‘as is’ and autoclaved controls.
Headspace samples were periodically removed and analyzed for toluene biodegradation. Aqueous samples were collected for the determination of biodegradation products and electron acceptors (volatile fatty acids, nitrate, and nitrite). Additional nitrate was added as needed to maintain nitrate reducing conditions. Finally, microbial community shifts between the biodiesel in the presence and absence of toluene were monitored by extracting total DNA in time series aqueous subsamples. Bacteria and Archaeal community shifts were evaluated using the fingerprint denaturing gradient gel electrophoresis (DGGE) technique.
Acknowledgements: This work was supported by FEDER funds through the Operational Program for Competitiveness Factors - COMPETE and National Funds through FCT – (Portuguese Science and Technology Foundation) under project numbers PTDC/AAG-TEC/4403/2012 and PTDC/AAC-AMB/113973/2009.
Leakage of chlorinated solvents into limestone aquifers from contamination in overlying deposits and long-lasting back diffusion from the limestone matrix pose an increasing threat to drinking water supplies, e.g. in Denmark. Often dechlorination of PCE and TCE contamination in limestone accumulates cis-DCE due to inadequacy of advection-based remediation technologies to deliver bioremediation additives. Therefore, there is a need for a remediation scheme capable of establishing contact between the contaminant, bacteria capable of degrading cis-DCE, and donor within the low permeable limestone matrix. EK offers some unique transport processes, which potentially overcome the diffusion limitations of ERD. A novel technology combines ERD and EK for enhanced delivery. The combined technology (EK-BIO) has shown promising results in the low permeable media clay. However, until now no studies have been performed with limestone.
A bench scale study of transport during EK-BIO in limestone was performed. Focus was on the transport abilities of EK for enhanced delivery of the donor lactate and a bacteria culture containing the dehalorespiring bacteria Dehalococcoides (Dhc) in limestone cores contaminated with cis-DCE. For the experiment, methods were developed for sampling of intact bryozoan limestone cores, saturation and contamination of the limestone cores using vacuum properties, and for monitoring throughout the limestone cores. In addition, an experimental set-up was designed to comply with the challenges of EK-BIO in limestone, e.g. the strict anaerobic bacteria, volatile contaminants and extreme pH developments prompted by electrode processes. The latter can be severe for the degrading bacteria if not managed.
An experimental set-up was successfully designed. However, issues with the recirculation pumping for neutralization of pH were experienced. Therefore, suggestions for improvements of the experimental design were made. The performed preliminary test and assessment of EK-BIO in limestone revealed a critical pH development in the electrode compartments. Nevertheless, the buffering capacity of the limestone maintained a pH range within the limestone appropriate for the Dhc. Observations on transport processes included faster diffusion in the control reactor without EK, than predicted. However, the delivery of the donor lactate was uneven, whereas migration of bacteria was not observed. For the reactor exposed to EK, lactate was delivered more evenly by electromigration causing an increase in electric conductivity. Furthermore, fermentation of lactate with an increase in pH indicated migration of bacteria by electrophoresis. Whereas, an initial test on EOF in limestone as well as the assessment of EK-BIO indicated that the properties of limestone hindered the establishment of EOF as opposing to clay.
During the experimental work on EK-BIO in limestone, EK was demonstrated to be promising in establishing enhanced contact between the donor lactate, bacteria and the chlorinated compound cis-DCE within the limestone matrix. Therefore, degradation is expected to occur. Thus, back diffusion limitations in the limestone matrix potentially are overcome, which is essential for the overall time perspective of a remediation.
Microbial populations and functions associated with the degradation of the aliphatic and PAHs fractions of crude oil in microcosms inoculated with an industrial polluted soil
Andrés Izquierdo1,2, Joaquim Vila1, Corinne Petit3, Pierre Peyret3, Alma Koch2 and Magdalena Grifoll1
1Department of Microbiology, University of Barcelona, Barcelona, Spain
2Laboratorio de Microbiología-Biotecnología, Universidad de las Fuerzas Armadas – ESPE, Sangolqui, Ecuador
3Laboratoire Microorganismes : Génome et Environnement - UMR 6023, Universite Blaise Pascal, Clermont Ferrand, France
The metabolic pathways for bacterial degradation of alkanes and PAHs are well established. However, there is still little information on the microbial processes dealing with alkylated derivatives of PAHs, which are the most abundant polyaromatic compounds in petroleum products. Despite several evidences exist pointing to their oxidation through two alternative pathways, the cometabolic monoxygenation of methyl groups or their accommodation through traditional PAH degradation routes, the actual environmental relevance of both processes is still unclear. In addition, there is limited information on the effect that the aliphatic fraction, predominant in oil derivatives, may have on the degradation of the aromatic fraction. Here, applying a combined phylogenetic and functional analysis of the microbial communities, we aim to decipher how the presence of aliphatics may influence a shift in the microbial processes determining the fate of PAHs, and especially alkyl-PAHs.
To gain insight into these processes, an industrial soil polluted with a mixture of oil derivatives, and previously remediated in biostimulated aerobic biopiles, was used as inoculum for lab-scale microcosms spiked with the aliphatic and/or aromatic fractions of a weathered crude oil. The microcosms were incubated for 30 days, and the fate of the different components of the aliphatic and aromatic fractions were monitored throughout the treatment by GC-MS. Shifts in microbial community structure and functions were monitored by high throughput sequencing (tag-encoded 454-pyrosequencing) and functional screens using PCR-amplification of monooxygenase genes (AlmA, AlkB and CYP153A) and functional microarrays including a number of dioxygenase gene probes.
The bulk of alkanes were completely removed from the media after 15 days of incubation and, interestingly, their presence had a synergic effect on the removal of PAHs, increasing their rates and extent of degradation (73 and 59%, with and without alkanes, respectively). The populations linked to the utilization of alkanes (Actinobacteria), PAHs (Alphaproteobacteria closely related to Sphingobium) and to the mixture of both fractions (a succession of Actinobacteria and Alphaproteobacteria) were identified. Their functional analysis revealed that, in accordance with the phylogenetic analysis, the biodegradation of alkanes was mainly catalyzed by alkane hydroxylases related to AlkB and CYP153A from Gordonia and Nocardia, while PAH biodegradation was mainly linked to biphenyl dioxygenases related to members of Sphingobium. In the presence of both fractions, the combined action of AlkB and CYP153A monooxygenases together with biphenyl-dioxygenases could explain the synergic effect of alkanes on PAH biodegradation.
Biomass from wetlands is a natural material able to decrease nitrate present in groundwater before the discharge to rivers or lakes. The desired predominant mechanism of nitrate removal is heterotrophic denitrification by supplying organic carbon that, additionally, enhances anoxic conditions in subsurface environment. Nevertheless, an excess of organic matter could activate other mechanisms as Dissimilatory Nitrate Reduction to Ammonia (DNRA). The leaching of these organic matter rich soils (e.g. peat) could be a mechanism to promote denitrification in deeper subsurface layers and, thus, avoiding high concentrations of organic matter and DNRA pathways.
In the present work, the assessment at laboratory scale of the denitrification capacity of leachates of wetland soils in which Phragmites sp and Arundo donax reeds have been growing for years has been studied. As a first step, samples of soils and degraded reed biomass were collected in two wetland zones in the Llobregat river basin (Barcelona) in February 2014.
Four leaching procedures (Soxhlet cycles, percolation in a column filled with material, shaking with water and lixiviation by using a normalized leaching test) were tested to extract the maximum of Dissolved Organic Carbon (DOC) at room temperature from the biomass samples. Values of DOC in the materials ranged from 10 to 31 mg•dm-3, obtaining the best results for normalized leaching test. The UV signal at 254 nm was also used to assess quantitatively the presence of aromatic compounds in the leachates. The ratio of this signal to DOC reported values from 0.03 to 0.06 A.U•l/mg, that are in the range of fulvic acid (0.05 A.U.dm3/mg). Nitrate in the leachates from all the biomass showed values above 20 mg•dm-3, with the exception of degraded Arundo donax in soil very close to the river that exhibit values below 2 mg•dm-3.
All these characterized leachates were filtered and used as matrix in two batch experiments, where nitrate and inoculum obtained from soil of the wetlands were mixed. The reaction was performed for a period of 5 to 12 days, showing complete denitrification when DOC was replaced by glucose 100 mg•dm-3.
A third leaching experiment was prepared by shredding green Arundo donax leaves sampled in May 2014. DOC of these leachates reached 523 mg•dm-3 and total nitrogen 49.8 mg•dm-3.In this case the leachate was not filtered.
Results showed a very low denitrification (< 10% nitrate elimination) for the three experiments for most of the materials, with the exception of the soil with degraded leaves of Phragmites sp and the green Arundo donax leaves that showed more than 50% and complete elimination of nitrate respectively.
As a conclusion, the leachates of biomass materials sampled in February were not able to leach important amounts of DOC and could not denitrify, with the exception of degraded Phragmite leaves sp. Soils showed the presence of UV-absorbing compounds that could be associated to complex organic matter as fulvic acids. Green Arundo donax leaves sampled in May allowed to obtain a leachate able to perform complete denitrification, mainly due to high DOC. In these vegetal materials nitrogen is important, as could contribute initially to the nitrate load of contaminant or release ammonium.
The present research work has been funded by the Spanish Ministry of Economy and Competitivity through project ATTENUATION (CGL2011-29975-C04-03, Natural and Induced Attenuation of groundwater pollution from agricultural and industrial sources).
Our objective was i) to assess the ability of microorganism from a plume to degrade chlorinated solvents to which they are exposed in situ and ii) to determine optimal substrate conditions to stimulate their ability to degrade these products. We monitored chloro-ethene and chloro-ethane, but also chloro-propane for which one little is known on its fate in the environment.
Three springs were selected at different distances from the Dense Nonaqueous Phase Liquid source in order to have one monophase water sample (W1) (15 m downstream the DNAPL) with perchloroethene (PCE), trichloroethene (TCE), dichloroethene (DCEcis and DCEtrans) are at the ppm level, a second water sample (W2) (250 m downstream) with these chloro-ethenes at the ppb level and a final diluted site (W3) (1.5 km downstream) with no PCE detected, TCE and DCEtrans at the limit of quantification level (2 ppb), and therefore with DCEcis (30 ppb) as main quantified contaminant. Vinyl chloride (VC) ranged from 0.3 to 0.008 ppm in these waters. Chloro-propanes were also found at the ppm level in the first water, especially the 1,2-dichloropropane (DCPa) (2.5 ppm).
Abundance of the total microbial community in these 3 water samples was assessed by qPCR (16S rRNA) and microscopic counting, and abundance of the bacterial community degrading chloro-ethene solvent was assessed by qPCR of reductive dehalogenase genes (pceA, tceA, pdrA, bvcA, vcrA). Water was placed in sacrificial batch units in triplicates with no substrate addition or with lactate (3 mM), acetate (3 mM), soya oil (15 g/L), molasses (0.7 g/L) as carbon substrate to stimulate reductive dechlorination. Degradation of the chlorinated solvent was monitored by GC/FID conditions every 2 weeks for lactate-spiked unit and every month for 4 additional conditions, during 5 months.
Preliminary results showed that after one-month incubation, concentrations in PCE, TCE, DCEtrans and VC, significantly decreased to a similar level in presence of lactate or molasses (p < 0.05) in water W1. However in W1, DCEcis and DCPa concentrations did not decreased after one-month incubation. In water W2, PCE, TCE, DCEtrans, VC and DCEcis significantly decreased after one-month incubation with lactate. In the water W3, DCEcis decreased after one-month incubation with lactate. Degradation analyses in the additional substrate conditions are under-going, also additional sampling dates to be performed are meant to generate biodegradation rate.
In conclusion, preliminary results suggest that i) bacteria able to degrade chlorinated solvent were present in the three tested water samples, ii) in the water W1, molasses and lactate would have similar potential to stimulate their activity, and iii) DCEcis degradation was not detected within one-month incubation in a sample with high level of PCE and TCE, such as W1, possibly because it is also the product of their degradation; when concentration in PCE and TCE were lower (W2) or not detected (W3), DCEcis degradation was initiated within a month.
The present study will provide valuable information for in situ bioremediation, and more specifically regarding choropropanes degradation. The present work will enable to select optimal conditions for further optimization in column units, then in a pilot-scale plant on site.
Anthropogenic organic chemicals like pesticides (2,4-Dichlorophenoxyacetic acid and Glyphosate) are deliberately released in major amounts to nearly all compartments of the environment. Soil as a complex matrix provide a wide variety of binding sites and are the major sinks for these compounds. Xenobiotics entering these complex systems may undergo various turnover processes. They can be degraded chemically (e.g. photolysis), biologically by microorganisms, volatilised leached to the groundwater, taken up by living organisms or immobilised.
The biological degradation of organic contaminants in soil generally results in the formation of metabolites, microbial biomass, CO2 and “bound” residues (non-available form). The extraction of these metabolites from soil allows the estimation of microbial activity; however, this activity could be modified thought the variation of physical, chemical or biological factors. Many studies have shown that parameters like the temperature, the organic matter content and the acidity of the soil are key factors to determinate the degradation rate of some organic contaminants and the way in which they are released into the environment.
Nowadays, enhanced transformation of contaminants into “bound” residues (non-extractable form) has been proposed as an alternative remediation method for polluted soils. Nevertheless, this kind of residues may pose a potential risk for environment due to their chemical structure and possible remobilization under different conditions. Some part of these residues may be “biogenic” because microorganisms use the carbon and nitrogen from the pollutant to form their biomass components (fatty acids, amino acids) what can result in the overestimation of the risk of “bound” residues in soil
MTBE has been added to gasoline since 1970's in order to improve engine performance and enhance air quality. Worldwide, It has been one of the highest production volume organic chemicals. In 1999, the annual world consumption of MTBE was more than 21 billion tons. However after only a few years of intense use, MTBE has become one of the major environmental concerns due to its chemical properties and widespread contamination of groundwater.
In situ aerobic bioremediation of MTBE is a cost effective technique which is used in many contaminated gasoline sites, but becomes increasingly more difficult as the concentrations of MTBE rise.
Due to the very high solubility of MTBE, many sites exhibit contamination by MTBE in the range of hundreds mg/L which are difficult to bioremediate. Moreover, the rates of degradation of MTBE and TBA are generally lower in comparison to the degrading rates of similar volatile organic compounds as Benzene, Toluene and Xylene. In many cases, the presence of those volatiles can even inhabit the degradation of MTBE.
The ability to biodegrade MTBE under aerobic conditions is possible by a limited number of microbial species, hence their presence in the contaminated site may become a limited factor for the successful remediation.
The remediation of high concentrations of MTBE in groundwater proved successful only when microflora resistant to high concentrations of MTBE was present and oxygen could be supplied in sufficient amounts.
Lab experiments proved relatively easy to provide these conditions relatively to actual field scale tests.
In this presentation we discuss the degradation of MTBE under high concentrations in laboratory and field scales. The laboratory experiments showed reduction of 40%-52% of the concentration of MTBE in relatively short time 12 days, when the initial MTBE concentration was up to 550 mg/L.
We will describe the enrichment of groundwater with an appropriate natural culture into highly contaminated groundwater, lacking the natural ability to biodegrade MTBE. This study provides insights into the conditions necessary for the degradation to occour.
Hydrophobic compounds such as polycyclic aromatic hydrocarbons (PAH) exhibit a strong tendency for adsorption on subsurface material. Due to the low solubility of such substances the determination of degradation kinetics is difficult. Reliable data for kinetic parameters such as growth rates and half-saturation constants are thus rare for PAH-degrading strains.
We performed degradation experiments with phenanthrene and pyrene and three Gram negative PAH-degrading strains (Novosphingobium pentaromativorans, Sphingomonas sp EPA505 and Sphingobium yanoikuyae) (Adam et al. 2014) as well as with two strains of mycobacteria (Mycobacterium rutilum and Mycobacterium pallens). Phenanthrene or pyrene were present as microcrystals in suspension concentrations from 10 to 400 mg/l, providing initially non-limiting conditions for growth. Chemical concentration and protein concentration or optical density (for the mycobacteria) were measured over 6 to 12 days. We developed and applied a numerical model for simultaneously calculating (i) dissolution kinetics of the substrate (dissolution from microcrystals into solution), (ii) substrate metabolism (Michaelis-Menten kinetics) and (iii) microbial growth (Monod kinetics with decay).
New and improved experimental kinetic data will be provided for PAH-degrading strains which are well-known from the literature and were isolated from various contaminated sites. The new dynamic model for desorption and metabolism describes mass-transfer of the substrate, taking simultaneously into consideration chemical activity, sorption and dissolution processes, metabolism and growth as well as cell maintenance and decay processes in non-steady-state. By inverse modeling we successfully determined kinetic parameters for the rates of dissolution, metabolism and grow from the experimental observations.
As a surprising outcome of the simulations, variations of the initial amount and of kinetic data of the degrader bacteria do not strongly affect the overall substrate turnover. As long as the dissolved concentration is sufficiently high, the degrader strains will grow, until a balance between dissolution of substrate and bacterial metabolism is reached. This balance was reached within a day or less in all experimental set-ups. For longer time periods, the amount of PAH that is ultimately degraded rather depended on the ad/desorption rates, and hereby on the substrate flux to the microbes, than on the Monod and Michaelis-Menten parameters of the strains. The model was subsequently used to simulate bioremediation options of aged PAH contamination in soils, for the optimization of treatment processes and for the assessment of residual, non-degradable concentrations remaining after various treatment options (see presentation of Rein et al., at AquaConsoil 2015).
Rein A, Trapp S, Adam IKU, Miltner A, Smith K, Marchal G, Karlson UG, Mayer P, Kästner M. 2015. Simulation of bioremediation options by microbial degradation of aged PAH contamination in soils. Presentation at AquaConsoil 2015.
Adam IKU, Rein A, Miltner A, Fulgêncio ACD, Trapp S, Kästner M. 2014. Experimental results and integrated modelling of bacterial growth on insoluble hydrophobic substrate (phenanthrene). Environ. Sci. Technol. 48 (15), 8717-8726.
Organic contaminants in the soil is a widespread problem that not only may cause damage to local biota, but also poses an ecological and health threat if the contaminants spread to groundwater aquifers and water ways. Therefore sites known to be contaminated should always be assessed preferable by performing both an ecological risk assessment and a health risk assessment. Monitored natural attenuation (MNA) is in some cases a reasonable approach, but risk assessment often calls for active remediation measures. For more than 20 years we have tested various approaches for enhancement of bioremediation of sites polluted by organic contaminants. Through collaboration between research facilities, contractors, and site owners, more than 30 actual sites presenting typical problems have been targets for testing and optimization, first by laboratory modeling, and then by applying lab experiences in pilot scale and application full scale. Samples from the sites were used in controlled laboratory conditions to build micro- and mesocosm- setups in which biological, physical, and chemical treatments were tested and combined, with the main goal of achieving optimal biostimulation and contaminant degradation. As soon as lab results were available, these were utilized for in situ field purposes. Lab and field tests were run in parallel, so that each new challenge in the field treatment generated modifications in the laboratory testing, and each new full scale treatment method was preceded by laboratory modeling. Successful bioremediation was achieved in most of the target cases. Lab testing also created the knowledge of when not to use bioremediation, and this can be regarded as one important utility of our results. While old contaminated sites often can rely on an adapted indigenous microbial community, new spill sites may be less responsive to mere biostimulation, and therefore more active treatment measures may be required. One bottleneck for a more widespread use of in situ methods is the great variability in the usefulness of each type of treatment. Vital for success is a thorough knowledge of the site and a variety of methods to choose from and, when necessary, to combine. Two successfull full sale treatments will be presented in detail. Both treatments were done in inhabited urban areas – biostimulation in the city-center of Mikkeli and “bioflushing” in Lintuvaara in Espoo. We have tested and optimized various combinations of biostimulation with nutrients and biosurfactans, bioaugmentation, extraction, electro-kinetic methods for liquid circulation and temperature elevation, and the use of previously contaminated soil as a seed for degraders. No single method to be used in situ can be named universal and useful in all cases. There always needs to be an array of methods to choose from, and it may be important to apply different methods at different stages of the process. Furthermore, every case should be evaluated separately, taking into account local conditions, type of contaminant, available time, etc. Only with these notions in mind is it possible to make in situ treatment a viable alternative to excavation of contaminated soil.
The purpose of the field-scale study was to evaluate the effectiveness of biostimulation and bioaugmentation for in situ biodegradation of chlorinated solvents in groundwater. Elevated levels of tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene, were detected in groundwater. The natural attenuation evaluation showed that reductive dechlorination was occurring in several of the on-site monitor wells where the dissolved oxygen (DO) concentrations were less than 1 mg/L. However, the oxidation reduction potential (ORP) significantly varied in on-site and off-site wells.
The results of bench-scale testing indicated that a variety of carbon substrates were effective at reducing the DO to levels that were favorable for reductive dechlorination. The lactate amended bioaugmented microcosms showed the highest level of reductive dechlorination, followed by EOS® amended. However, the indigenous microbial population was not able to successfully degrade PCE to ethene. When a microbial consortium including Dehalococcoides was added to the microcosms, complete reductive dechlorination was observed.
A pair of recirculation wells was installed to inject the carbon source and microbial population into the groundwater. After a push-pull test was performed to evaluate the mobility of the microbial amendment, lactate was injected to promote highly reduced conditions in the groundwater. Once the ORP was less -150 mV, the Dehalococcoides consortium was injected into the groundwater and recirculated using the paired recirculation wells.
Within 3 months after carbon substrate injection, more than a 70% reduction in PCE and TCE was observed in the downgradient monitor well. Likewise, there was a significant decrease in ORP in the impacted wells. This presentation will discuss how the amendments impacted the chlorinated solvent concentrations, microbial community and chemistry of the groundwater in the area around the recirculation wells compared to non-impacted wells.
ENHANCED REDUCTIVE DEHALOGENATION OF CHLOROETENES BY APPLICATION OF CHEESE WHEY IN SITU: A CASE STUDY WITH FIELD, CHEMICAL AND MOLECULAR BIOLOGY ANALYSIS
Monika Stavělová
Iva Dolinová 2), Maria Brennerová 3)
1) AECOM CZ s.r.o., Trojska 92, 171 00, Prague, CZ
2) Technical University of Liberec, Studentska 1402/2, 46117,Liberec, CZ
3) Institute of Microbiology, AS ČR, v.v.i., Videnska 1083, 142 20 Prague, CR
Dehalogenation of the chlorinated ethenes (CE) to the non-toxic end-products ethane and ethene is the most efficient remediation technique - enhanced reductive dehalogenation (ERD). Remedial companies have over 50 year’s practical experience in the CE remediation. The competition among the remedial companies is enormous. The main efforts are focused to cost efficient monitoring, and reducing of time of remediation and remedial price. Nowadays, the requirements for final remediation are much more stringent, since the remedial limits are comparable with the criteria for lowest pollutant concentration several years ago. We still need to understand the transformation of CE depending on the geological environment, changes in oxidative-reductive conditions and microbial activity. Since the ERD is frequently halted to 1,2-dichloroethene (1,2-DCE) or to the carcinogenic vinyl chloride (VC), the interpretation of analytical data together with molecular biological analysis for present dechlorinating bacteria and reductive dehalogenase genes can be used for controlling of the remediation procedure. A model site is characterized using optimized methodology elaborated by the Institute of Microbiology (IM), Technical University of Liberec (TUL) and the technical part of the project team - AECOM CZ (AE). Groundwater (GW) samples were collected in dynamic state using Micro purging methodology up to the hydrochemical parameters stabilization point (pH, redox-potential, conductivity). The collected samples were analyzed by accredited laboratory for: CE content including VC, organic substrate content using COD, CH4, ethane, ethylene, H2S+S2-, SO42-, PO43-, NO3-, NO2-, NH4+, Fe2+, Mn2+, Sr and K+. Attention was paid to minimization of exposure of all samples to oxygen. In situ anaerobic reactor management – AE: In advance, a baseline of the contaminated site was determined for the complete range of field measurements, laboratory and molecular genetic tests. Cheese whey was then repeatedly injected into the wells containing chloroetenes at intervals of several months. The amount of cheese whey applied to each well was depended on the progress of contaminant transformation. The primary contaminants PCE and TCE were nearly completely transformed to 1,2-cis DCE, and VC started to accumulate, thus, indicating transformation to the nontoxic final products. Molecular-genetic analyses - IM: A main result of the cooperation includes optimization of the DNA extraction from the GW and soil samples using an advanced automated laboratory tool - MaxwellTM 16 System: filtration of 3-5 liters of GW through 0,2 µm nylon membrane, preextraction of DNA, and isolation of DNA in the automated device. Detection of key bacterial species involved in the respiration of CE, and genes (vcrA a bvcA) coding reductive dehalogenases, enzymes crucial for the dehalorespiration pathways (transforming PCE →TCE→ DCE→VC→ ethylene) was carried out using polymerase chain reaction (PCR) method. Primer sets targeting Dehalobacter sp., Dehalococcoides sp., Geobacter sp., Sulfurospirillum sp., Desulfitobacterium sp. Additionally, the presence of sulphate-reducing bacteria was monitored, thus, indicating any changes of the in-situ oxidation-reductive conditions during remediation. Nanosamplers – TUL: An alternative approach for acquiring DNA from groundwater is tested using stationary samplers containing nanofiber components. An optimal way of DNA/RNA stabilization during transport from site to laboratory had been examined. Detection of ERD key bacterial species and vcrA a bvcA was made and compared with the results from continual monitoring of the groundwater during the remediation activities.
This research is co-financed by Technology Agency of the Czech Republic, project Techtool (TA0202534).
The increasing presence of organic micropollutants in different segments of the water cycle poses a serious threat to future water resources. These micropollutants are currently being detected at low concentrations in groundwater and surface water used for drinking water. Current monitoring (chemical analyses) gives an indication of the presence of these micropollutants. However, little is known about natural attenuation, that is processes that contribute to removal of micropollutants under in situ conditions. This information is required to assess and predict the long term risks of contamination of drinking water intakes.
Natural attenuation of pesticides in the subsurface is an important process that protects groundwater resources from these organic micropollutants. However, in order to properly rely on natural attenuation, information on biodegradation rates and tools for assessing degradation capacity are required. While biodegradation of many of the pesticides currently found in monitoring wells has been researched, often these studies have been performed under optimized laboratory conditions. The results from such experiments, including degradation rates, pathways, and molecular markers for assessing biodegradation, can thus not be easily translated to describe degradation under in situ conditions.
The work presented here is a step towards developing an understanding of natural attenuation under in situ conditions in the subsurface. A multi-disciplinary approach is taken, whereby information on contaminant degradation, subsurface geochemistry, and microbial community structure are integrated into a thorough understanding of the environmental conditions associated with natural attenuation. To this end, laboratory degradation experiments as well as field measurements are performed. In addition to determining degradation rates under various environmental conditions, molecular tools are also applied in order to characterize the microbial populations required for biodegradation. This work is thus a step towards understanding degradation under in situ environmental conditions and developing molecular based tools for monitoring degradation capacity. Together, these results provide valuable information on the natural attenuation of pesticides in subsurface systems.
In-situ bioremediation is a commonly used remediation technology to clean up the subsurface of an organic-contaminated site. The process of in-situ bioremediation involves complex and uncertain relationships among biomass, contaminant, nutrients, and appropriate control actions. This study discusses the development of a simulation model-based, dynamic, and multi-objective to support the control action for a bioremediation site, which involves substantial complex and uncertain data.
To investigate remediation performances, a subsurface model was employed to simulate contaminant reactive transport. In a complex geochemistry which involves different organics compounds the interactions among the system components are difficult to understand, and it is practically impossible to accurately predict potential subsurface reactions. In the first step, a reactive transport model was formulated to evaluate and decrease the uncertainties about the sources terms. In the second step, the knowledge provide by the model can be acquired and incorporated in a predictive model to optimize the control action of the remediation process. The developed system has been applied on real site data. Application of the proposed approach to a bioremediation process in a real site, which involves substantial uncertain data on the sources terms, indicated that it was effective to understand a complex geochemistry and to provide support in real-time process control of the in-situ bioremediation systems.
The proposed in-situ bioremediation process optimization is done through the application of common groundwater flow and reactive transport models (MODFLOW, MT3DMS, PHT3D) to provide to modelers and decision maker with a cost effective tool which is transferable from the present study to other site managed by in-situ bioremediation.
At several sites in the Netherlands Bioclear stimulated biological degradation of volatile organic chlorinated compounds (VOC) successfully. The technique used is based on direct injection of carbon source and, if needed additional specific dechlorinating bacteria Dehalococcoides spp. (DHC). This technique is, instead of most in situ remediation techniques, very well applicable in poorly permeable soils like clay and peat. Direct push injections are typically used to remediate a source zone. Research and field experience have shown that chlorinated ethenes concentrations close to the maximum solubility can be biologically degraded.
Direct injections are performed with a small injection machine. Protamylasse can be used as carbon source. Protamylasse does not only contain organic carbon but contains also enough nutrients for the growth of dechlorinating bacteria. Protamylasse is an organic waste stream from the potato starch industry. Which is an environmentally friendly (and cheaper) alternative compared to chemically produced carbon sources like lactate, acetate or hydrogen release compound. If injection of dechlorinating bacteria is desired, a culture with a high concentration of dechlorinating bacteria is obtained from a lab.
A distance between the injection points of 1 to 3 meters is used to ensure appropriate distribution of the additions. Not only soils consisting of sand but also low permeable soils like peat and clay can be remediated with this technique. Depending on the type of soil, injection can be performed to around 30 m-bgl. Because the injection machine is relatively small, injection can be performed in hard-to-reach urban locations. Injection at an angle of 45 degrees makes it possible to inject under buildings. Injection takes typically one to three weeks, depending on the size of the project. After the injections, the ‘passive phase’ starts. During the passive phase the degradation of chlorinated ethenes will take place and can be monitored.
In this presentation 5 different examples will be given of locations that were succesfully treated by means of direct injections. Concentration of contaminants varies to a maximum of 140,000 µg/l DCE. Different soil types were treated with this technique. In the presentation we will also focus on the remediation results, time, costs and sustainability.
Background and Objectives. Emulsified vegetable oil (EVO) applications to support anaerobic
bioremediation can be advantageous from a cost basis in that a long-lasting organic carbon
source can be delivered to the subsurface during infrequent injection events. Because these
applications may serve as the sole form of remedial activity over a several year period,
understanding the EVO distribution achieved and the resulting concentration of dissolved
organic carbon (DOC) that can be sustained and available for microbial use is critical to
successful design. To date, EVO loading rates (injected concentration) and distribution extent
(droplet transport) have generally been defined by stoichiometric electron donor calculation or laboratory-derived oil to soil loading ratios. Results from multiple field efforts indicate that these projections can significantly underestimate the required EVO loading and these values must be evaluated on a case-by-case basis to confirm droplet retention (adherence or straining) and provide sufficient organic carbon distribution for treatment within the targeted area.
Approach/Activities. Using fluorescent dye tracers and the combination of both total and
dissolved organic carbon fractions, pilot and full-scale EVO injection applications have been
conducted at numerous sites to evaluate differences between multiple EVO substrates, injection techniques (direct push and permanent wells), and overall treatment strategy (grid-style points or treatment barrier) to further refine EVO application design. Results from these activities indicate that the extent of EVO droplet straining can be more than one order of magnitude higher than that predicted based on current literature values. This can result in insufficient distribution of EVO and DOC following injection and limit overall treatment performance and remedial success. In addition to droplet straining behavior, differences in both dye tracer and organic carbon wash out have been used to characterize DOC strength and groundwater residence time within multiple injection areas. Coupled with volatile organic compound (VOC) treatment data, these wash out rates can help determine the required residence time for optimal system design.
Results/Lessons Learned. A summary of the EVO droplet straining behavior and extent
observed at multiple field sites will be presented and will be coupled with a detailed case study to illustrate the key design considerations for practitioners applying EVO. The case study results include dose response data (tracer dye and EVO transport characterization) used to confirm droplet retention at monitoring wells within the radial extent of injection; and results of a method of moments approach used to evaluate the groundwater velocity within two different hydrostratigraphies (fine sand and gravelly sand) to illustrate differences in droplet distribution, achievable DOC concentrations, and groundwater residence time through the EVO injection area. These data were then correlated with the VOC treatment performance achieved. Results indicate that the groundwater velocity between the two units varied by two-fold (0.07 m/day versus 0.14 m/day), which resulted in differences in sustained DOC (273 milligrams per liter [mg/L] versus 155 mg/L, respectively) and the overall extent of chlorinated VOC treatment over a nine-month time period (reduction of 95% versus 45%, respectively).
Background/Objectives.
1,4-dioxane is an emerging contaminant found in groundwater at sites throughout the United States. Historically used as a stabilizer for chlorinated solvents and hence routinely detected at chlorinated impacted sites. It’s known for being highly mobile and recalcitrant to typical remedial applications that rely on volatilization and biodegradation due to its physical and chemical properties. In-situ chemical oxidation (ISCO) is a promising alternative to pump and treat applications using ex-situ advanced oxidation processes. Selecting a suitable ISCO strategy for in situ remediation of both 1,4-dioxane and associated co-contaminants can be challenging and may vary with site-specific geology and geochemistry. To inform the design of full-scale remediation, ARCADIS conducted treatability studies using groundwater impacted by 1,4-dioxane and co-contaminants from two sites with different geological settings (bedrock and heterogeneous sands and silts). The objectives of the treatability tests were to evaluate the efficacy of treatment using sodium persulfate under multiple activation strategies, determine the most effective activator, and approximate the oxidant and activator dosing requirements for field-scale application.
Approach/Activities.
ISCO treatability studies were conducted in a similar manner at two sites with different geochemical environments (gneiss bedrock and heterogeneous silts/clays/sands). Groundwater with either soil or crushed rock were treated with up to 50 g/L sodium persulfate in both tests. The testing included control samples, ambient (no activation), chelated iron, and alkaline (sodium hydroxide) activations to generate the free radical reaction mechanisms. Multiple phases of treatability studies were conducted to determine optimal ratios of activator and oxidant at each site. Byproducts of the reactions, including dissolved metals, acetone and chlorinated methanes and ethanes were measured as part of the study. The overall effectiveness of the oxidant and chelators were evaluated, including the effectiveness of 1,4-dioxane treatment, co-contaminant destruction, and the magnitude of metal mobilization and chlorinated byproduct production.
Results/Lessons Learned.
The results of the treatability studies show that 1,4-dioxane can be successfully eliminated with sodium persulfate using multiple activation mechanisms. Despite different geochemical environments, sodium hydroxide-activated sodium persulfate treatments demonstrated the most promising results at both sites. A 4:1 molar ratio of sodium hydroxide to sodium persulfate was observed to be most effective in treating 1,4-dioxane and co-contaminants while minimizing byproducts. The results of the treatability tests demonstrate that multiple activation methods are capable of near complete destruction of 1,4-dioxane and that specific site geochemistry impacts the removal efficiency and rate of byproduct formation. Preliminary data from field applications at each site utilizing activated sodium persulfate with sodium hydroxide will also be presented.
Collectively, ARCADIS has conducted over 150 independent treatability tests for remediation via in situ chemical oxidation (ISCO) across our global remediation network. The results from treatability testing were used select site-specific remedies and activation chemistries for both common and emerging contaminants. This presentation will present an analysis of the dataset generated from this large suite of testing and summarize the key lessons learned for ISCO reagent and activator selection and field implementation, including:
• Potential oxidant-contaminant interactions
• Oxidant demand based on contaminant type and mass
• Soil oxidant demand from organic carbon, reduced metals, and anions
• Aquifer characteristics (i.e. groundwater flow velocity) and activation kinetics
In addition, the effects of different activation approaches, such as alkaline desorption/surfactant effects and generation of organic intermediates from the oxidation of certain contaminants will be discussed. This information gleaned from treatability testing and implementation supports the existing literature pertaining to what techniques work best and provides information where there are gaps in the current literature.
In situ chemical oxidation (ISCO) is an effective technology for clean up site contaminated by organic compounds. This remediation involves the introduction of a chemical oxidant into the subsurface for the purpose of transforming groundwater or soil contaminants into less harmful chemical species. Commonly applied oxidants are permanganate, hydrogen peroxide (with or without iron), ozone and persulfate.
For ISCO to be effective, the oxidant must contact the contaminant. This can be difficult in many soils and aquifers where natural heterogeneities can result in flow bypassing around lower permeability zones or where the presence of natural compounds can generate non-productive reactions that consume oxidant compromising the adequate oxidant transport and distribution.
Environmental conditions and site characterization have to be taking into account in order to optimize the ISCO application. A few studies have been carried out in saltmarsh areas under Mediterranean climate conditions. This work has been developed in Southern Spain in an 1.5 ha site where several hydrocarbon leakage from ancient fuel storage tanks and transport facilities have been reported. The working area is a complex site with a substrate consisting of irregularly distributed anthropic deposits over marsh sediments, usually clayey; both anthro- pogenic and natural marsh deposits show a remarkable heterogeneity in their morphological and physicochemical properties. The work area presents a water table with high spatial and temporal variability, in a context of a Mediterranean climate with mild and wet winters and warm and dry summers. In such conditions, a large number of prospections have been performed in order to assess the type of materials present, its thickness and its spatial distribution. This activity, carried out with pedological criteria, has enabled to define horizons or levels where initial physicochemical and morphological characterizations is needed. In parallel, groundwater sampling has been carried out by establishing a network of monitoring wells, which allowed the initial hydrochemical characterization of the site and the establishment of groundwater levels, which were subsequently monitored. After a preliminary laboratory and pilot tests, ISCO was applied in the working area.
Hydrogeochemical characteristics (basic pH and high carbonate, sulphate and chloride concentration) involved the use of iron chelates to keep the iron in solution and to increase peroxide lifetime. Hydraulic characteristics (low permeability of shell level, possible preferential pathways – anthropogenic fill with more permeability – and shallow depth of groundwater) determined well construction, well layout, delivery strategy and injections sequence. Regarding injection strategy, 36 wells were perforated and a total of 14,000 L of pressurized hydrogen peroxide and catalyst solution with iron and hydrogen peroxide stabilizer were injected separately to increase the radius of influence. Taking into account hydrogeological characteristic of the site and the gas generation due to reagent injection, the injection flow were less than 1 L/min to avoid high pressure that besides might generate surfacing.
Preliminary results indicate the efficiency of the experimental design under the adverse conditions of the site (heterogeneous hydraulic conditions, low permeability and the elevated presence of scavengers). A general TPHs contamination reduction in 80% of the wells closed to 57%. This validation of the design allows to optimize the ISCO treatment, currently carried out, in the working area in order to reduce the contamination according to the project objectives.
This work has been performed within the framework of the BIOXISOIL (LIFE 11 ENV/ES/505) project funded by the EU through the LIFE Programme.
Fe-containing zeolites are a promising material for the removal of organic contaminants from groundwater, since they can be tailored for an optimal combination of two functions: I) Zeolites with appropriate channel structure and SiO2/Al2O3 ratio have excellent adsorption efficiencies for small organic molecules such as MTBE, BTEX or chlorinated solvents. II) The ion exchange sites located in the pore channels and cages of zeolites allow dispersion and stabilization of isolated iron ions, which are highly active in redox reactions. Thus, Fe-loaded zeolites have been shown to function as heterogeneous Fenton-like catalysts over a wide pH range including neutral conditions [1-3].
With respect to ex-situ treatment of contaminated groundwater, Fe-zeolites can be an interesting alternative to activated carbon since Fe-zeolite adsorbers offer the option of easy on-site regeneration by flushing with H2O2 solution [1].
In the framework of the EU project NanoRem a novel concept for in-situ chemical oxidation based on the application of colloidal Fe-zeolites is developed. The basic idea is to apply a solid adsorbent and catalyst for Fenton-like oxidation in the form of a suspension, which can be injected into the aquifer in an initial step, separate from the subsequent addition of H2O2. The colloidal particles are transported over a certain distance and deposited on the aquifer sediment, where they form an active zone in the preferred groundwater flow paths. Using a stationary solid catalyst has the advantage to allow a mixing with the oxidant in the subsurface, i.e. at the location of the contamination. By this means, the injection of mixtures of catalyst and H2O2, causing vigorous reactions and thus safety issues known from conventional Fenton-based ISCO, could be avoided. In addition, prior to oxidant injection the Fe-zeolite zone could be initially used as a sorption barrier. By this means aqueous phase concentrations of contaminants are reduced and further spreading of plumes is prevented. At the same time, the sorption barrier can enrich contaminants from a larger volume of water before injecting the oxidant into it. This would correspond to an increased radius of influence of the ISCO process and a more efficient utilization of H2O2.
This contribution summarizes results from lab experiments on the selection and optimization of Fe-zeolites with respect to transport and distribution in saturated porous media as well as adsorption and catalytic oxidation of various groundwater contaminants (MTBE, trichloroethene (TCE), 1,2-dichloroethane (DCA) and toluene). Structure-property correlations were derived by screening various zeolite types differing in framework type and SiO2/Al2O3 ratio for adsorption of model contaminants. Channel diameter (determined by the framework type) and surface hydrophobicity (determined by SiO2/Al2O3 ratio) are the most influential factors in this process. Even though high-silica zeolites have a low ion-exchange capacity and thus can take up only limited amounts of iron ions, it was possible to obtain sufficiently active catalysts for oxidation of adsorbed contaminants by H2O2 [3].
Soluble (modified) biopolymers were applied in order to obtain appropriate suspension stability and transport properties of the colloidal zeolites. Due to the fact that these soluble polymers are excluded from the inner pore volume of the zeolites by virtue of their size, no significant adverse effects on contaminant adsorption and catalytic performance of the Fe-zeolites are observed.
Particle mobility was studied in 1D-column experiments using standard materials (porous media and water) and protocols developed in the NanoRem project. For stabilized Fe-BEA-35 (the first prototype Fe-zeolite selected), promising results on mobility were obtained, showing breakthrough of 85% particle mass concentration from a 20 cm column (washed quartz sand 0.3 - 0.8 mm, soft water, u = 10 m/d, cparticle,in = 1 g/L, cstabilizer = 1.5 g/L).
In batch experiments Fe-BEA showed high catalytic activity in Fenton-like oxidation even in very hard water (pH 8.2). Reaction rates of the model contaminants were increasing in the order DCA < MTBE < TCE < toluene, which is in accordance with the selectivity predicted for a reaction driven by OH-radicals.
In addition, column experiments simulating the cycle of catalyst infiltration and immobilization, contaminant adsorption and degradation were conducted using MTBE as model contaminant. Fe-BEA-35 which was loaded on washed quartz sand at a mass fraction of 1 wt% showed stable adsorption and catalytic properties over three cycles of infiltration of MTBE-contaminated water (10 mg/L MTBE in very hard water, u = 1 m/d) with intermittent regeneration by H2O2 infiltration (10 g/L H2O2 in very hard water, u = 1 m/d).
Acknowledgements: This work was supported by funding from European Union within the NanoRem project.
[1] A. Georgi, R. Gonzalez-Olmos, R. Köhler, F.-D. Kopinke, Separation Science and Technology, 45 (2010) 1579.
[2] R. Gonzalez-Olmos, F. Holzer, F.-D. Kopinke, A. Georgi, Applied Catalysis A: General, 398 (2011), 44.
[3] R. Gonzalez-Olmos, K. Mackenzie, F.-D. Kopinke, A. Georgi, Environmental Science and Technology, 47 (2013), 2353.
OPTIMUM HYDROCARBON TECHNOLOGIES (OHT) is developing a new and innovative technology (later referred to as “the OHT process”) to extract hydrocarbons from polluted soils & water.
The OHT process uses a polymeric material (the agent) which is hydrophobic, oleophilic and capable of reversibly adsorbing hydrocarbons.
The hydrocarbons are selectively transferred from their matrix onto the agent in a mixing/adsorption vessel and can then be recovered from the oil-rich agent. The desorbed agent can then be reused in additional process cycles. The process operates at ambient temperature.
This presentation recalls the main principles of this innovative technology and highlights the latest results of this research program. It also summarizes the numerous possible applications of this technology, ranging from the remediation of hydrocarbon polluted soils to the production of oil from oil sands and including the treatment of the effluent waters produced by the petroleum industry.
Remediation of a tar related contamination: watercourse in agricultural area
Debeuf A.1, Mulders S.²
1 OVAM, Stationsstraat 110, 2800 Mechelen, Belgium, P: +32 15 284 531, F: +32 15 284 408, adebeuf@ovam.be
2 Tractebel Engineering, Arianelaan 7, 1200 Brussel, Belgium, P: +32 2 773 99 11, F: + 32 2 773 99 00, info@technum-tractebel.be
Topic: Excavation and ex-situ treatment of contaminated watercourse in agricultural area: remediation targets, practical approach and difficulties during implementation
Willebroek-Noord (120 ha) is an obsolete industrial area situated between Antwerp and Brussels. Despite its excellent strategic location, about 50 ha have been unused during the last decades. The existing soil contamination and residual waste materials complicate the redevelopment of this area. From a former gas plant, situated in the southern part of Willebroek-Noord, tar-containing wastewater was until 1978 drained in the Gorrebroekloop, a small watercourse that partially flows through agricultural area. Over time the tar-contaminants (mainly benzene, PAH’s and mineral oil) have been spread from the sludge layer into the underlying sediments and aquifers. Due to flooding and sludge deposits on the banks the topsoil of the nearby agricultural land has also been contaminated.
This first remediation phase provides in the removal of the topsoil (because of the human-toxicological risk for agricultural use), the highly contaminated sludge and a maximum amount of heavily contaminated subsoil to approximately 2 m below ground level (to prevent the spreading of pollution through surface water).
A total amount of about 60.000 tons was excavated and transported for ex-situ remediation. After the filling up with clean soil the watercourse was reshaped. To protect the banks against erosion biodegradable coconut mattings were used.
During a second phase the deeper contamination (to 15 m below ground level) will be remediated with in-situ techniques.
The following challenges made of this at first sight simple but large-scale excavation an interesting and instructive project:
- The site was inaccessible for heavy traffic that was needed for the excavation and transportation of the tons of soil. Along the entire watercourse (about 600 m) topsoil was removed and a temporarily 7 m wide road was constructed with a package of 50 cm crushed stones.
- It was necessary to keep the farmers well informed before and during the remediation, because part of their land was temporarily unavailable. The farmers were paid a fee for structural damage of the soil and for the loss of a part of their crop.
- A high pressure oxygen pipe that crosses the watercourse at a shallow depth, a gas pipeline and a high tension line pylon right along the excavation made some adjustments and extra safety regulations during the works necessary.
- To reduce the odour nuisance for the residents several extra measures were considered. A rotary atomizer was constantly available on the site. PID measurements were done to check the volatile organic compounds.
Preference: poster presentation
At the former low temperature carbonization plant „Schwelerei Deuben“, massive soil and groundwater contaminations are caused by residual and free oil phase (LNAPL) which have a lasting adverse effect on the groundwater especially with phenols, BTEX, PAH and ammonium.
The LNAPL reached the site boundary as mobile local floating and incoherent blobs. The contaminant plume in the groundwater has exceeded the boundary significantly. A conventional pump & treat system with a hydraulic supported oil skimming effectively prevents the further propagation of the groundwater contamination.
The mid-term remediation strategy is to achieve a stationary groundwater plume without further contaminant migration applying enhanced natural attenuation. To reach this goal stepwise, innovative remediation technologies for enhanced oil recovery (EOR) have been tested to optimize the site remediation strategy and to enable site specific permissions for the technology application by the authorities.
Two pilot tests for the EOR-remediation are implemented by the in-situ technologies mobilizing solvent soil flushing (solvent: 100% n-butanol) in sandy layers and in-situ thermal treatment with thermal wells (THERIS method) in silty, loamy formations. Both methods complement regarding the hydrogeological boundary conditions. Required values have been achieved during the pilot field tests demonstrating the efficiency of the applied EOR methods. Design and conduction of both methods have been confirmed technically and legally within an acceptable time and cost expenditure:
• significant reduction of residual oil phase and its harmful effect (contaminant emissions) from the unsaturated zone,
• recovery or immobilization of mobile oil phase from the unsaturated and the saturated zone,
• stimulation of an efficient aerobic in-situ degradation of the remaining contaminant mass flux in the groundwater as a permanent ENA-process.
Process-related objective of mobilizing solvent soil flushing is to convert moderate mobile oil-phase into a swelling oily mobile phase by infiltration and spreading of n-butanol as a solvent fluid at the capillary fringe zone increasing this way the relative permeability. The mobile phase is recovered at wells as much as possible (preliminary remediation). In a second step, the resting ratio of butanol in the residual oily phase and in the groundwater has to be reducted by intensive water flushing. Finally, aerobic in-situ degradation of dissolved butanol and dissolved contaminants has to be stimulated by the injection of oxygen gas.
Process-related objective of the thermally EOR-THERIS is the mobilization of residual oil phase by reducing viscosity and surface tension due to increased subsurface temperature
Mobile oil phase was recovered by a multi-phase fluid pump and skimming, soil vapour extraction avoided an uncontrolled migration of volatile compounds like BTEX. Significant thermally enhanced oil phase mobilization could be observed by reaching temperatures at and above approximately 70°C in large areas of the pilot test.
Since 2013, both EOR techniques have been proved in pilot test areas of approximate 100 m², embedded into the continued pump & treat system.
The pilot tests at the former low temperature carbonization plant Deuben take place by order of the Lausitzer und Mitteldeutsche Bergbauverwaltungsgesellschaft mbH, and are coordinated and managed by GFI Dresden.
The Fenton Process is based on the production of the highly reactive hydroxyl radical (OH•), which is resulting from the reaction between hydrogen peroxide (H2O2) and ferrous ions Fe(II) under acidic conditions. The oxidation system, which relies on Fenton’s reagent, can be employed to treat various types of waters and wastewaters containing a range of organic pollutants like phenols, polycyclic aromatic hydrocarbons, pesticides, formaldehyde, wood preservatives, plastic additives and rubber chemicals. The treatment of polluted waters using Fenton process results in reduction of toxicity, improvement in biodegradability, odour and colour removal. The Fenton process can also be employed as a post- or a pre-treatment step in the treatment of high strength polluted waters with extremely toxic and refractory nature. In the Fenton process, iron and hydrogen peroxide are the two major chemicals that determine not only the operation costs but also the treatment efficacy (Zhang et al., 2009). The objective of the present investigation was to examine the effectiveness of Fenton Process in treating polluted waters of different origins. The performance of Fenton oxidation employed in the treatment of soil washing solution, landfill leachate and phenolic water was investigated with an aim of determining their optimum reaction conditions. For this purpose, all experiments were performed in the batch system. The influence of H2O2, FeSO4 concentrations and reaction time on the removal efficiency were investigated. The pH of reaction mixture was adjusted at the start of the reaction. Required amounts of FeSO4 and H2O2 were added simultaneously into the solution and then the mixture was shaken using a mechanical shaker. The progress of reaction was followed by monitoring the disappearance of the contaminant and chemical oxygen demand (COD). The results indicated that the Fenton process was successful in the treatment of polluted waters. Organic pollutants (e.g. phenol, fluorene, etc) were efficiently removed by the Fenton process. Removal efficiency depended on the reaction time and Fe(II) and H2O2 concentrations. 83% of phenol was degraded and 60% of COD was removed at conditions of H2O2 500 mg/L, Fe2+ 30 mg/L, phenol 250 mg/L and pH 3.0. Similarly, in the treatment of soil washing solution 40% of COD was removed under optimum conditions, which were 2 hours reaction time, 2% H2O2 concentration and 1/50 Fe/H2O2 ratio. In the treatment of landfill leachate, a COD removal of 66% was obtained for 5000 mg/L hydrogen peroxide and 30 min reaction time.
Keywords: polluted waters, Fenton process, system optimisation