U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Treatment Technologies


Halogenated Alkenes

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General Resources | Case Studies | Case Studies: cis-1,2-Dichloroethene | Tetrachloroethene (PCE) | Case Studies: PCE | Trichloroethene (TCE) | General Resources: TCE | Case Studies: TCE | Abstracts: TCE

The chlorinated ethenes are best biodegraded through anaerobic or cometabolic (both anaerobic and aerobic) processes. The more oxidized the ethene (more chlorine atoms) the easier it is to dechlorinate, which explains why on some sites the process stops at cis-1,2-DCE. It is also possible to degrade 1,2-DCE aerobically if it is the only contaminant of concern (i.e., TCE and PCE are not present in significant quantities).

1,1-Dichloroethene can be degraded aerobically or anaerobically. Although it is an industrial chemical, it is generally found in the environmental literature as a degradation product. No bioremediation projects were identified that addressed a 1,1-DCE DNAPL site.

Dichloropropene (1,3-DCP) is generally degraded aerobically and also can be hydrolyzed to 3-chloroallyl alcohol. While there can be environmental concern for soil fumigants containing 1,3-DCP, it is rarely found as a DNAPL and no general or specific references to bioremediation involving it as a DNAPL were found.

General Resources

Adobe PDF LogoBioaugmentation for Remediation of Chlorinated Solvents: Technology Development, Status, and Research Needs
Environmental Security Technology Certification Program (ESTCP), 126 pp, Oct 2005

Reviews the state of bioaugmentation science at the present time, summarizes the current status of this rapidly evolving innovative technology, identifies the key issues confronting the science, and evaluates the lessons learned from current practical applications. This technology 'snapshot' may be useful to remedial project managers faced with selecting, designing, and implementing a bioaugmentation strategy.

Characterization of a Microbial Consortium Capable of Rapid and Simultaneous Dechlorination of 1,1,2,2-Tetrachloroethane and Chlorinated Ethane and Ethene Intermediates
E. Jones, M. Voytek, M. Lora, and J. Kirshtein.
Bioremediation Journal, Vol 10 No 4, p 153-168, Dec 2006
View abstract Description of WBC-2 Culture

Presents a study of mixed microbial cultures enriched from contaminated wetland sediment at Aberdeen Proving Ground, MD. The "West Branch Consortium" (WBC-2) was found to be capable of degrading 1,1,2,2-TeCA, TCE, cis- and trans-1,2-DCE, 1,1,2- TCA, 1,2-DCA, and VC to ethene and ethane. The dominant species was Clostridiales, including Acetobacteria, which comprised 65% of the bacterial clones, with Bacteroides (14%), and epsilon Proteobacteria (14%) also present. Dehalococcoides was present at about 1% in the microbial population. The WBC-2 consortium provides opportunities for the in situ bioremediation of sites contaminated with mixtures of chlorinated ethenes and ethanes.

Coupling Aggressive Mass Removal with Microbial Reductive Dechlorination for Remediation of DNAPL Source Zones: a Review and Assessment
J.A. Christ, C.A. Ramsburg, L.M. Abriola, K.D Pennell and F.E. Loeffler.
Environmental Health Perspectives, Vol 133 No 4, p 465-477, 2005

Reviews available laboratory and field evidence that supports the development of a treatment strategy combining aggressive source-zone removal technologies with subsequent promotion of sustained microbial reductive dechlorination. Results suggest that, for the favorable conditions assumed in these calculations (i.e., statistical homogeneity of aquifer properties, known source-zone DNAPL distribution, and successful bioenhancement in the source zone), source longevity may be reduced by as much as an order of magnitude when physical/chemical source-zone treatment is coupled with reductive dechlorination.

Adobe PDF LogoD6-2 Status Report on Technological Reliability for Demonstrated Soil and Groundwater Management Technologies with Special Focus on the Situation In Europe, Part 2: Update on Bioremediation Only
Eurodemo Project (GOCE) 003985, 71 pp, 2007

To encourage the application of enhanced in situ bioremediation technologies across Europe, EuroDemo has prepared this report on bioaugmentation and biostimulation techniques used to address chlorinated aliphatic hydrocarbon contamination, illustrating them with case studies of successful implementation at sites in the United States.

DCE/VC Stall Tool
U.S. Navy, Naval Facilities Engineering Command, Environmental Restoration Technology Transfer, Multimedia Training Tools Website, 19 pages, 2011

At some sites, conditions for complete reductive dechlorination of PCE or TCE to ethene are not present, and degradation stalls at DCE and/or VC. Three basic requirements must be met to form a complete reductive dechlorination pathway: sufficient electron donor (a fermentable carbon source), appropriate redox potential (strongly reducing conditions) in the aquifer, and microbial communities capable of complete dechlorination of PCE to ethene. This tool provides RPMs with the information necessary to recognize DCE and/or VC stall and explores its biological and/or environmental causes, along with potential solutions.

Adobe PDF LogoDevelopment and Validation of a Quantitative Framework and Management Expectation Tool for the Selection of Bioremediation Approaches at Chlorinated Ethene Sites
Lebron, C., T. Wiedemeier, J. Wilson, F. Loeffler, R. Hinchee, and M. Singletary.
ESTCP Project ER-201129, 178 pp, 2015

The overarching project objective was to develop and validate a framework for making bioremediation decisions based on site-specific physical and biogeochemical characteristics and constraints. The key deliverable is called BioPIC, an easy-to-use decision tool for estimating and integrating the impact of quantifiable parameters on NA and microbial remedies to achieve detoxification of chlorinated ethenes. The quantitative framework and BioPIC were beta-tested for chlorinated ethenes (mainly PCE, TCE, and daughter products) degradation at four sites. Additional information: BioPIC tool and other reports

Adobe PDF LogoDevelopment of a Design Tool for Planning Aqueous Amendment Injection Systems: User's Guide
R.C. Borden, et al.
ESTCP Project ER-0626

A simple spreadsheet-based tool developed to assist in the design of injection-only systems for distributing emulsions or soluble substrate allows quick comparison of the relative costs and performance of different injection alternatives and identification of the design best suited to site-specific conditions. Emulsion Design Tool (2008)Adobe PDF Logo; Soluble Substrate Design Tool (2012) Adobe PDF Logo.

Adobe PDF LogoDraft Technical Protocol: A Treatability Test for Evaluating the Potential Applicability of the Reductive Anaerobic Biological In Situ Treatment Technology (RABITT) to Remediate Chloroethenes
J.J. Morse, B.C. Alleman, J.M. Gossett, S.H. Zinder, and D.E. Fennell.
AFRL-ML-TY-TR-1998-4522, 94 pp, 1998

Describes a comprehensive approach for conducting a phased treatability test to determine the potential for employing RABITT at any specific site. It is not meant as a guide for designing either full or pilot-scale in situ biotreatment systems for chlorinated ethenes or any other contaminant. The protocol guides the user through a decision process in which information is collected and evaluated to determine if the technology should be given further consideration. RABITT will be screened out if it is determined that site-specific characteristics, regulatory constraints, or other logistic problems suggest that the technology will be difficult or impossible to employ, or if a competing technology clearly is superior.

Adobe PDF LogoElucidation of the Mechanisms and Environmental Relevance of cis-Dichloroethene and Vinyl Chloride Biodegradation
Cox, E.
SERDP Project ER-1557, 170 pp, 2012

Major results of this project can be summarized as follows: (1) JS666 remains the only isolated organism known to mediate aerobic oxidation of cDCE to CO2, and DNA-based molecular biological tools exist to track its presence and fate during bioaugmentation projects; (2) significant advances were made in understanding the pathway, mechanisms, and enzymes associated with aerobic oxidation of cDCE in JS666; (3) anaerobic oxidation of cDCE and/or VC under iron- or manganese-reducing conditions could not be confirmed, despite substantial efforts with materials from many sites; (4) suspected anaerobic oxidation of VC may in fact be aerobic oxidation to CO2 at extremely low levels of oxygen in the subsurface; and (5) compound-specific isotope fractionation of carbon occurs in both anaerobic and aerobic microbial degradation of ethane, allowing the use of CSIA to assess ethene degradation as a possible means to explain poor ethene mass balance in enhanced in situ bioremediation and MNA projects.

Adobe PDF LogoEngineered Approaches to In Situ Bioremediation of Chlorinated Solvents: Fundamentals and Field Applications
U.S. EPA, Technology Innovation Office.
EPA 542-R-00-008, 144 pp, 2000

Provides an overview of in situ bioremediation to remediate chlorinated solvents in contaminated soil and groundwater and describes degradation mechanisms for chlorinated solvents, enhancements of these mechanisms by the addition of various materials and chemicals, design approaches, and factors to consider when selecting and using the technology. Contains 9 case studies of field applications.

Adobe PDF LogoField Push-Pull Test Protocol for Aerobic Cometabolism of Chlorinated Aliphatic Hydrocarbons
Y. Kim, M. Azizian, J. Istok, and L. Semprini.
Environmental Security Technology Certification Program (ESTCP), 83 pp, 2005

Presents a protocol for a newly developed field technology—the single-well push-pull test—for evaluating the feasibility of using in situ aerobic cometabolic processes to treat groundwater contaminated with chlorinated solvent mixtures.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team.
BioDNAPL-2, 173 pp, 2007

Based upon the results of 6 case histories of in situ bioremediation (ISB) of DNAPLs, this report provides state and federal regulators having oversight of the cleanup of DNAPL sites with evidence supporting ISB as a viable cleanup strategy.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Ethene: DNAPL Source Zones
Interstate Technology & Regulatory Council (ITRC), Bioremediation of DNAPLs Team. BioDNAPL-3, 138 pp, June 2008

This publication systematically lays out the technical and related regulatory considerations for in situ bioremediation (ISB) of chlorinated ethene dense DNAPL source zones, providing information related to site characterization requirements, treatment system application and design criteria, process monitoring, and process optimization. The ability of ISB technology to enhance the dissolution and desorption of nonaqueous-phase contaminants to the aqueous phase, where they can be degraded by the microbial population, depends on the spatial distribution of DNAPL mass in the subsurface (e.g., pool/ganglia ratio) and the ability to deliver amendments throughout this architecture.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: A Resource Guide
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team, 46 pp, 2007

This resource guide provides a compilation of relevant scientific and technical literature on the bioremediation of chlorinated ethene DNAPLs designed to help regulators, technology practitioners, site owners, and others develop a consistent approach to the basic principles, terminology, and technical features of bioremediation. The guide attempts to address the most critical aspects of the technology, but it is not intended to be an exhaustive treatise on the subject either in breadth or depth.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Solvent with Natural Gas
D.E. Rabold.
WSRC-MS-95-0303, 10 pp, 1996

Describes a bioremediation system for the removal of chlorinated solvents from groundwater and sediments. Involves the injection of natural gas (as a microbial nutrient) in situ through an innovative configuration of horizontal wells.

Adobe PDF LogoMass Transfer from Entrapped DNAPL Sources Undergoing Remediation: Characterization Methods and Prediction Tools
T.H. Illangasekare, J.M. Marr, R.L. Siegrist, et al.
Strategic Environmental Research and Development Program (SERDP), 437 pp, 2006

Evaluated 4 source zone technologies in an investigation of mass transfer and tracer partitioning in physically heterogeneous DNAPL sources undergoing remediation: (1) biotreatment, (2) in situ chemical oxidation (ISCO), (3) surfactant-enhanced dissolution, and (4) thermal treatment. Fundamental knowledge was generated to improve and develop tools for evaluating the impact of remediation technologies on DNAPL distribution in heterogeneous systems. Experiments and modeling at column, flow cell and large tank scales were designed to understand how parameters that quantify laboratory-scale processes contributing to mass transfer and parameters that quantify the processes can be scaled up to describe and simulate the field-scale behavior, and to test hypotheses that mass transfer coefficients for entrapped DNAPL sources change during remediation.

Adobe PDF LogoMicrobial Mineralization of cis-Dichloroethene and Vinyl Chloride as a Component of Natural Attenuation of Chloroethene Contaminants under Conditions Identified in the Field as Anoxic
Bradley, P.M.
U.S. Geological Survey Scientific Investigations Report 2012-5032, 41 pp, 2012

Oxygen-based microbial mineralization of DCE and VC can be substantial under field conditions characterized as anoxic. A modified framework is detailed for assessing the potential importance of oxygen during chloroethene biodegradation.

Adobe PDF LogoOverview of In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team.
BioDNAPL-1, 89 pp, 2005

Presents a technological overview of in situ bioremediation (ISB) and some of the issues to consider when selecting and designing an ISB system for remediation of chlorinated DNAPL source zones.

Adobe PDF LogoPrinciples and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents
Air Force Center for Environmental Excellence (AFCEE), 457 pp, 2004

Describes the state of the practice of enhanced anaerobic bioremediation, explains the scientific basis of enhanced anaerobic bioremediation, and discusses relevant site selection, design, and performance criteria for various engineered approaches in current practice. 2010 Addendum: Loading Rates and Impacts of Substrate Delivery for Enhanced Anaerobic BioremediationAdobe PDF Logo

Adobe PDF LogoProtocol for Enhanced In Situ Bioremediation Using Emulsified Edible Oil
R. Borden.
Environmental Security Technology Certification Program (ESTCP), 100 pp, 2006

Discusses use of emulsified oils for bioremediation, impact of emulsified oils in contaminant fate and transport, injection and distribution of emulsified oils, and approaches to full scale application of emulsified oils.

Adobe PDF LogoRemediation of Chlorinated Solvent Contamination on Industrial and Airfield Sites
Air Force Center for Environmental Excellence (AFCEE), 136 pp, 2000

Provides an overview of technologies (including enhanced biodegradation) that might be employed to remediate source zone and dissolved-phase chlorinated solvents.

Adobe PDF LogoTechnical and Regulatory Requirements for Enhanced In Situ Bioremediation of Chlorinated Solvents in Groundwater
Interstate Technology and Regulatory Cooperation (ITRC) In Situ Bioremediation Subgroup, ISB-6, 122 pp, 1998

Provides guidance to those considering the deployment of enhanced in situ bioremediation of chlorinated solvents in groundwater. Deals specifically with classes of remediation systems designed to remediate or prevent further migration of chlorinated solvents through use of enhancements applied to accelerate solvent biodegradation.

Adobe PDF LogoTwo Novel Methods for Enhancing Source Zone Bioremediation: Direct Hydrogen Addition and Electron Acceptor Diversion
C. Newell, C. Aziz, P. Haas, J. Hughes, and T.A. Khan.
Proceedings of the Sixth International Symposium on In-Situ and On-Site Bioremediation, 4-7 June 2001, San Diego, California. 8 pp, 2001

Discusses direct injection of hydrogen into a source zone and electron acceptor diversion where competing electron acceptors are diverted around the source zone, thereby greatly increasing the rate of reductive dechlorination in the source zone.

Abstracts of Journal Articles

Bioaugmentation for Accelerated In Situ Anaerobic Bioremediation
D.E. Ellis, E.J. Lutz, J.M. Odom, R.L. Buchanan, Jr., C.L. Bartlett, M.D. Lee, M.R. Harkness, and K.A. Deweerd.
Environmental Science and Technology, Vol 34 No 11, p 2254-2260, 2000

Discusses a successful anaerobic bioaugmentation demonstration that used an ethene-forming culture from DOE's Pinellas site in Largo, FL, to inoculate a pilot area in a TCE-contaminated aquifer at Dover Air Force Base. Although dechlorination of the TCE was occurring at the Dover base, it had stalled at cis-1,2-DCE. After a lag period of about 90 days from injection, the now predominantly 1,2-DCE plume began to degrade to ethene.

Biodegradation of High Concentrations of Tetrachloroethene in a Continuous-Flow Column System
M. Isalou, B.E. Sleep, and S.N. Liss.
Environmental Science and Technology, Vol 32 No , p 3579-3585, 1998

Discusses a laboratory study of the anaerobic biodegradation of high concentrations of PCE. Concentrations of PCE fed to the column ranged to over 600 µM with methanol added as electron donor. VC was the end product of the process for the first 21 months, at which point significant conversion of VC to ethene was detected. Ethene was produced in the presence of PCE and TCE. Varying methanol:PCE molar ratios had little effect on the transformation of PCE and TCE to VC; however, VC degradation was much more sensitive. The absence of PCE in the system for a 5-month period did not result in the loss of PCE degradation capability of the consortium.

Biologically Enhanced Dissolution of Tetrachloroethene DNAPL
Y. Yang and P.L. McCarty.
Environmental Science and Technology, Vol 34 No 14, p 2979-2984, 2000

This article describes an experiment to determine if PCE can be degraded at high dissolved concentrations and the effects of these concentrations on microbes that might compete with the dehalogenating organisms for electron donors. The experiment showed that degradation could occur at high concentrations and that these concentrations could be inhibitory for competing microorganisms with the favorable result of better utilization of electron donor substrate for dehalogenation. Another finding was that the dissolution rate was enhanced by the biodegradation.

Bioreactive Barriers: A Comparison of Bioaugmentation and Biostimulation for Chlorinated Solvent Remediation
J.M. Lendvay, F.E. Loeffler, M. Dollhopf, et al.
Environmental Science and Technology, Vol 37 No 7, P 1422-1431, 2003

Compares bioaugmentation and biostimulation degradation rates in a chloroethene-contaminated aquifer. A contaminant mass balance was developed to quantify key dechlorinating populations and their relation to the rate of chloroethenes removed. A Dehalococcoides consortium containing PCE-to-ethene dechlorinating inoculum was used for bioaugmentation, and it resulted dechlorination of sorbed and dissolved chloroethenes to ethene within 6 weeks. Continuous lactate and nutrient injection were used for biostimulation. Dechlorination occurred following a 3-month lag period. These results indicate the potential for bioreactive barriers to use reductively dechlorinating populations to control the migration of chloroethene plumes.

Comparison between Donor Substrates for Biologically Enhanced Tetrachloroethene DNAPL Dissolution
Y. Yang and P.L. McCarty.
Environmental Science and Technology, Vol 36 No 15, p 3400-3404, 2002

Discusses the effects that different substrates may have on the degradation rates of PCE. High rates of degradation also have a direct relation on NAPL dissolution rates that can decrease the time required to cleanup. The study found that some substrates may produce extensive methanogenesis, which reduces PCE transformation and hence dissolution rates of the DNAPL. These results suggest that DNAPL remediation strategies should consider ways to control competitive methanogenic utilization of donor substrates.

Comparison of Anaerobic Dechlorinating Enrichment Cultures Maintained on Tetrachloroethene, Trichloroethene, cis-Dichloroethene, and Vinyl Chloride
M. Duhamel, S.D. Wehr, L. Yu, H. Rizvi, S. Seepersad, S. Dworatzek, E.E. Cox, and E.A. Edwards.
Water Research, Vol 36 No 17, p 4193-4202, 2002

This lab study used an anaerobic mixed microbial culture taken from soil and groundwater at TCE contaminated site. This culture was divided into four separate samples and one sample was amended with PCE, another with TCE, the third with cis-1,2-DCE and the fourth with VC. In all the samples the chlorinated ethenes were rapidly, consistently, and completely converted to ethene. These cultures were could rapidly dechlorinate of VC but could not dechlorinate 1,2-DCA, which means they did not contain Dehalococcoides ethenogenes. Addition of chloroform and 1,1,1-TCA inhibited the cultures ability to dechlorinate the four chlorinated ethenes. The most strongly inhibited was the conversion of VC to ethene. Differences in culture composition developed which included the loss of the VC enrichment culture's ability to dechlorinate PCE. Analysis of the cultures identified three different DNA sequences that were phylogenetically related to D. ethenogenes. Based on the results and substrate utilization patterns, it is apparent that significant mechanistic differences exist between each step of dechlorination from TCE to ethene.

Competition for Hydrogen within a Chlorinated Solvent Dehalogenating Mixed Culture
Y. Yang and P.L. McCarty.
Environmental Science and Technology, Vol 32 No 22, p 3591-3597, 1998

This paper discusses a study that examined the competition between dehalogenators and other microorganisms in a benzoate-acclimated methanogenic mixed culture. The dehalogenators appeared to compete best against methanogens and homoacetogens when the hydrogen level was maintained between 2 and 11 nM. Control of the hydrogen concentration appears to be key in favoring dehalogenation of chlorinated solvents over other hydrogen using processes.

Growth of a Dehalococcoides-Like Microorganism on Vinyl Chloride and cis-Dichloroethene as Electron Acceptors as Determined by Competitive PCR
A.M. Cupples, A.M Spormann, and P.L. McCarty.
Applied and Environmental Microbiology, Vol 69, p 953-959, 2003

Discusses the development of a competitive PCR (cPCR) assay to enumerate the growth of a Dehalococcoides-like microorganism, bacterium VS. The growth of bacterium VS was linked to dehalogenation of VC and cis-1,2-DCE. VS used hydrogen as the electron donor and VC and cis-1,2-DCE as the electron acceptors. An important limitation of the cPCR assay is its inability to determine whether cells were active or inactive, which is an essential consideration for kinetic studies.

Reductive Dechlorination of Chlorinated Ethene DNAPLs by a Culture Enriched from Contaminated Groundwater
R.B. Nielsen and J.D. Keasling.
Biotechnology and Bioengineering, Vol 62 No 2, p 160-165, 1999

Groundwater from a TCE/PCE contaminated aquifer studied to observe the microbial degradation of PCE and TCE to ethene showed a first-order rate dependence with respect to substrate at low PCE concentrations and a zero-order dependence at high concentrations. TCE and VC had first-order dependence at all substrate concentrations. VC had little or no effect on the initial rate of TCE dechlorination. With subsaturating concentrations of PCE/TCE, vinyl chloride accumulated prior to its dechlorination to ethene; however, in the presence of a DNAPL in equilibrium with the aqueous phase, the chlorinated ethene was dechlorinated to ethene, with little accumulation chlorinated intermediates.

Case Studies

More examples of bioremediation are available in which the technology is used as part of a treatment train.

Adobe PDF LogoApplication of Biodegradable Oils (VOS™) for Treatment of Chlorinated Ethenes in the Vadose Zone
Richardson, S.D., J.B. Elkins, B.D. Riha, J.V. Noonkester, and B.B. Looney.
Pollution Engineering 44(4):(2012) [a Pollution Engineering White Paper]

Vadose Oil Substrate (VOS™) is a thixotropic (shear thinning) formulation of biodegradable oil, water, nutrients, buffers, and dechlorinating bacteria that sequesters and biodegrades slow-diffusing CVOCs from unsaturated soils. Field testing of the compound began in February 2010 at the Savannah River Site to address discrete point sources of CVOC contamination within the 120 to 130 ft thick vadose zone, the result of leaks from joints in a sewer line of process wastewaters containing PCE, TCE, and minor amounts of 1,1,1-TCA. The injection of 230 gallons of VOS(tm) resulted in a rapid and significant decrease in CVOC gas concentration, generation of CVOC daughter products, a decrease in oxygen concentration, and an increase in carbon dioxide and methane production. Additional information: Slide presentationAdobe PDF Logo

In Situ Bioremediation (Anaerobic/Aerobic) at Watertown, Massachusetts
Federal Remediation Technologies Roundtable Cost & Performance Database, 2000

The Watertown site has been used since the late 1800s for a variety of operations, at one time a coal gas manufacturing plant, later a metal plating shop, and currently a manufacturing facility for electric switch assembly. A field demonstration of the Two-Zone Plume-Interception Treatment Technology developed by Harding Lawson Associates was conducted at the Watertown site under EPA's SITE program. The system was a groundwater recirculating cell that consisted of three injection wells and three extraction wells and covered a surface area of approximately 10 ft by 20 ft, with wells screened from 13 to 20 ft bgs. Nutrients and a carbon source were injected into the groundwater through the three upgradient wells and extracted through the three downgradient wells. Lactic acid was used in the anaerobic conditions, and ORC® socks plus methane in aerobic conditions. Under anaerobic conditions, TCE in groundwater was reduced by reductive dechlorination (from 12 mg/L to less than 1 mg/L) and there was an overall reduction of about 80% of the total VOC mass in one well. Following the establishment of aerobic conditions by the ORC® socks, the concentrations of cis-1,2-DCE and VC began decreasing.

Cost and Performance Technology Report: In Situ Bioremediation Using Hydrogen Release Compound (HRC®) at Four Dry Cleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2005

In situ bioremediation using HRC® was conducted at four dry cleaner sites contaminated with chlorinated solvents. The concentration of contaminants varied by site with levels of cis-1,2-DCE and TCE as high as 7.3 g/L and PCE as high as 22 g/L. Levels of TCE and PCE in soil were as high as 0.8 g/kg and 53 g/kg, respectively. At three sites (Arlington, Former Colony, and Former Prestonwood), full-scale remediation was carried out, while at Ted's Cleaners, a pilot scale operation was performed. After 2 HRC® injection events at Arlington (one in May 2000 and the second in August 2002, confirmatory sampling indicated that the dissolved contaminants remained below cleanup goals and cleanup goals for the soil were not exceeded. A certificate of completion was issued for this site. At Former Colony, contaminant concentrations in groundwater have decreased since HRC® injection in October 2000. Groundwater monitoring is being continued at the site. At former Prestonwood, PCE concentration in one monitoring well increased from 15,000 µg/L to 23,500 µg/L 2 years after HRC® injection. Additional groundwater monitoring has been recommended for the site. After a September 2002 injection event at Ted's Cleaners, no effect of HRC® injection had been observed on downgradient contaminant concentrations approximately 5 ft away as of June 2004. Additional testing is being done at the site, including the polymerase chain reaction test.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team.
BioDNAPL-2, 173 pp, 2007

Contains the following case studies: (1) cleanup of a TCE residual source area and a dissolved-phase plume at the Test Area North site of Idaho National Engineering and Environmental Laboratory; (2) a pilot-scale demonstration to evaluate the effects of biological activity on enhancing dissolution of an emplaced PCE DNAPL source at Dover National Test Site; (3) a TCE cleanup field study at Cape Canaveral's Launch Complex 34, Kennedy Space Center; (4) a PCE demonstration project undertaken by ARCADIS at a private-sector U.S. site; (5) a cleanup of PCE groundwater impacts at an active dry cleaner located in a strip mall in Portland, OR; and (6) use of Emulsified Oil Substrate (EOS®) to remediate a TCE source area at the Tarheel Army Missile Plant, Burlington, NC.

Adobe PDF LogoIn-Situ Bioremediation of Chlorinated Hydrocarbons: an Assessment of Projects in California
California Department of Toxic Substances Control, Office of Pollution Prevention and Technology Development.
OPPTD Document No. 1217, 163 pp, 2006

During an evaluation of the performance of in situ bioremediation (ISB) systems at 5 sites in California, the reviewers observed several recurring issues. The project case studies illustrate the reviewers' recommendations for avoiding common ISB problems.

Case Studies: cis-1,2-Dichloroethene

Enhanced In Situ Bioremediation Process at the ITT Roanoke Site, Roanoke, VA
Federal Remediation Technologies Roundtable Cost & Performance Database, 2000

The ITTNV plant in Roanoke, VA is an active manufacturing plant that produces night vision devices and related products. Groundwater contamination resulted from tank leaks of chlorinated and nonchlorinated compounds used as manufacturing cleaning solvents. The contaminated area included groundwater in fractured bedrock. An injection well was used to deliver a mixture of air, nitrous oxide, triethyl phosphate, and methane at 15-30 psi and 20 scfm to bioremediate a mixture of chlorinated ethanes, VC, and cis-1,2-DCE. Of the four contaminants analyzed, two (cis-1,2-DCE and VC) met the treatment goal of 75% reduction (with a 0.1 level of significance) in the zone of influence.

Innovative Technology Evaluation Report: Earth Tech Inc.'s Enhanced In-Situ Bioremediation Process
U.S. EPA, National Risk Management Research Laboratory.
EPA 540-R-00-504, 16 pp, 2003

Describes a demonstration of the PHOster™ process, which involves delivery of a gas-phase mixture of air, nutrients, and methane to contaminated groundwater in bedrock. Chemicals of concern in this demonstration were chloroethane, 1,1-DCA, cis-1,2-DCE, and VC.

Tetrachloroethene (PCE)

The degradation process for PCE is generally PCE→TCE→cis-1,2-DCE (with the possibility of minor amounts of trans-1,2-DCE and 1,1-DCE)→VC→ethene. At each step, different types of degradation are possible. The table below displays the potential processes for the chloroethenes.

Degradation Process PCE TCE DCE VC
Aerobic Oxidation N N P Y
Aerobic Cometabolism N Y Y Y
Anaerobic Oxidation N N P Y
Direct Anaerobic Reductive Dechlorination Y Y Y Y
Cometabolic Anaerobic Reduction Y Y Y Y
Abiotic Transformation Y Y Y Y

Adapted from Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents, AFCEE, 2004.

Y=Documented in the literature
N=Not documented in the literature
P=Potential for reaction to occur but not well documented in the literature

Abstracts of Journal Articles

Effect of Dechlorinating Bacteria on the Longevity and Composition of PCE-Containing Non-Aqueous Phase Liquids under Equilibrium Dissolution Conditions
C.S. Carr, S. Garg, and J.B. Hughes.
Environmental Science and Technology, Vol 34 No 6, p 1088-1094, 2000

Discusses a laboratory study that investigated the effects of biodegradation of dissolved-phase PCE on the dissolution rates of PCE from a PCE-containing NAPL. Comparisons between biotic and abiotic reactors indicated that dechlorination resulted in a factor of 14 increase in PCE removal rates from the NAPL. The authors estimated that that in biotic reactors, total chlorinated ethene removal from the NAPL would be achieved in 13 days as compared to 77 days in abiotic reactors.

Inoculation of a DNAPL Source Zone to Initiate Reductive Dechlorination of PCE
D.T. Adamson, J.M. McDade, and J.B. Hughes.
Environmental Science and Technology, Vol 37 No 11, p 2525-2533, 2003

Describes a laboratory study to investigate bioaugmentation combined with biostimulation of a simulated PCE DNAPL. An active and stable dechlorinating culture was added to the study area and dechlorination activity was observed within 2 weeks. TCE and cis-1,2-DCE were observed initially, and reductive activity was increased with the addition of a source of hydrogen (HRC). After 225 days of operation, cis-DCE was the predominant compound present. Production of VC and ethene lagged the formation of TCE and cis-DCE. The detection of Dehalococcoides species in the source culture and in the simulated aquifer post inoculation indicated that the culture had the ability to degrade the PCE beyond cis-1,2-DCE. TCE and cis-1,2-DCE were observed in the source zone, but VC and ethene were not. This indicates that dechlorination beyond cis-DCE may be limited to regions downgradient of the source zone.

Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene
X. Maymo-Gatell, Y.T. Chien, J.M. Gossett, and S.H. Zinder.
Science, Vol 276, p1568-1571, 1997

PCE can be reductively dechlorinated to ethene by mixed anaerobic microbes. Strain 195, a eubacterium that appears capable of dechlorinating PCE to ethene, was grown using hydrogen as the electron donor and PCE as the electron acceptor.

Case Studies: PCE

Adobe PDF LogoBiodegradation of Dense Non-Aqueous Phase Liquids (DNAPLS) through Bioaugmentation of Source Areas - Dover National Test Site, Dover, Delaware: ESTCP Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP), Project ER-0008, 59 pp, Aug 2008

This demonstration was conducted to determine if bioaugmentation can stimulate complete dechlorination of a DNAPL to nontoxic end products, as well as increase the mass flux from a source zone when biological dehalorespiration activity is enhanced through nutrient addition and/or bioaugmentation. The demonstration was able to prove that biological systems can be applied to promote enhanced dissolution of a PCE DNAPL source zone. Conservatively, the study appears to demonstrate an average increase in mass discharge ranging from 2.2 to 4.5 during the bioaugmentation phase relative to baseline (groundwater extraction only) conditions. If the increase in degradation rates is insufficient to enhance DNAPL removal significantly, rapid biodegradation of the high VOC concentrations typically encountered in DNAPL source zones will provide biological containment of the groundwater plume, thereby reducing cleanup times and/or reducing the O&M cost of conventional containment using pump and treat.

Contemporary Cleaners, Orlando, Florida
State Coalition for the Remediation of Drycleaners, Case Profiles Database, 2000/2006

HRC®, a hydrogen release donor, was injected into the subsurface to enhance bioremediation of PCE and its degradation products. Degradation of PCE occurred stalled at cis-1,2-DCE despite the presence of Dehaloccocodies sp., likely because of the low pH at the site. Administration of a buffering agent was considered. After 152 days, groundwater monitoring indicated that mass reduction achieved for contaminants was PCE 96%, cis-1,2-DCE 36%, TCE 51%, and VC 58%. Concentration of cis-1,2-DCE had increased with no increase in VC.

In Situ Bioremediation Using Hydrogen Release Compound® or Molasses at Six Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable, 2001

In situ bioremediation was conducted at 6 drycleaner sites contaminated with chlorinated solvents, primarily TCE and PCE, as contaminants in groundwater. TCE and PCE concentrations varied by site, with levels of PCE in groundwater as high as 1,230 mg/L and TCE as high as 8.3 mg/L. The remediation approaches, including full-scale and demonstration-scale projects, involved the subsurface injection of substances to promote bioremediation. In situ bioremediation was promoted with of HRC® at 5 sites (one injection event each) and molasses at one site (6 injection events over a period of 20 months). Reductions in PCE and TCE concentrations and increases in PCE and TCE biodegradation products were reported for all five HRC® sites. At the molasses site, PCE concentrations in groundwater decreased to below analytical detection limits and the site was closed.

Demonstration of Bioaugmentation at Kelly AFB, Texas
Federal Remediation Technologies Roundtable Cost & Performance Database, 2007

After augmentation of the aquifer with KB-1 (a prepared commercial culture of halorespiring bacteria) to address PCE, TCE, and their degradation products, complete dechlorination of PCE to ethene was observed. Following the successful demonstration of the bioaugmentation technology, the robustness of the KB-1 culture was tested through the deprivation of electron donor and then the addition of sulfate. The results indicate that (1) the KB-1 culture was able to compete with, and survive among, the indigenous microbial population, and (2) bioaugmentation may not require continuous attention following inoculation at sites where the natural attenuation requirements are met.

Hayden Island Cleaners Portland, Oregon
State Coalition for the Remediation of Drycleaners, Case Profiles Database, 2001/2006

Hydrogen Release Compound (HRC) was used to stimulate the microbial degradation of a PCE release. Initial concentrations of PCE in the groundwater ranged up to 1,230 mg/L, which indicates the presence of a DNAPL. After 15 months, an 87% mass reduction in PCE was achieved. Substantial increases of daughter products TCE and cis-1,2-DCE also were observed.

Removal of Perchloroethylene within a Silt Confining Layer Using Hydrogen Release Compound
Irwin, J.A. and D.E. Marsh.
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy 15:227-235(2010)

A former drycleaner in the Connecticut River basin had PCE up to 250 mg/L in perched groundwater above a silt-layer aquitard. Vapor intrusion (VI) into a commercial building was mitigated by a passive vapor barrier and an SVE system. HRC® injection was implemented for source control and VI mitigation, and multiple injections over an 8-yr period in the sandy unit above the aquitard achieved significant PCE reduction in the silt layer below. MIPs deployed to assess the extent of additional area within the perched groundwater needing treatment showed PCE peripheral to the initial treatment zones. Additional HRC injection to address PCE both vertically and laterally over a wider area further decreased PCE concentrations in perched groundwater and soil gas.

Adobe PDF LogoSteam-Enhanced Extraction and Thermal Conduction Heating for In Situ Treatment of Tetrachloroethylene
Cole, J., M. Singer, S. Offner, D. Williamson, J. Galligan, D. Phelan, S. Fournier, G. Heron, D. Timmons, P. King, and S. Trussell.
Eighth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May 20-24, 2012, Monterey, California. Battelle Press, Columbus, OH. 25 slides, 2012

In situ thermal remediation to remove PCE DNAPL from the site's soil and groundwater at Arnold Air Force Base, TN, relied on both thermal conduction heating and steam injection. SVE wells and multiphase extraction wells completed between 45-90 ft bgs were located within and around the treatment zone for hydraulic and pneumatic gradient control during treatment. After 16 months of system operation in 2010-2011 and removal of ~165,000 lbs of PCE, the thermal systems achieved the revised remedial goals established under the performance-based contract. Additional information on this project was published in EPA's Technology News & Trends newsletter of October 2012.

Trichloroethene (TCE)

The degradation process for TCE is generally TCE→cis-1,2-DCE (with the possibility of minor amounts of trans-1,2-DCE and 1,1-DCE)→VC→ethene. At each step, different types of degradation are possible. The table below displays the potential processes for the chloroethenes.

Degradation ProcessPCETCEDCEVC
Aerobic OxidationNNPY
Aerobic CometabolismNYYY
Anaerobic OxidationNNPY
Direct Anaerobic Reductive DechlorinationYYYY
Cometabolic Anaerobic ReductionYYYY
Abiotic TransformationYYYY

Adapted from Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents, AFCEE, 2004

Y=Documented in the literature
N=Not documented in the literature
P=Potential for reaction to occur but not well documented in the literature

General Resources: TCE

Adobe PDF LogoIn Situ Bioremediation of TCE-Contaminated Groundwater
B.J. Travis and N.D. Rosenberg.
LA-UR-98-2605, NTIS: DE99001639, 22 pp, 1998

Presents a biokinetics model that includes microbial competition and predation processes. Predator species can feed on the microbial species that degrade contaminants. Simulation studies show that species interactions must be considered when designing in situ bioremediation systems.

Adobe PDF LogoReductive Anaerobic Biological In-Situ Treatment Technology (RABITT) Treatability Test. Interim Report
Environmental Security Technology Certification Program (ESTCP), 16 pp, 2001

Describes the results of demonstrations of reductive anaerobic biodegradation at three DoD facilities: Cape Canaveral Air Station, FL, Alameda Point, CA, and Ft. Lewis, WA. A fourth facility (Camp Lejeune, NC) is named, but the demonstration was still in progress during the preparation of this report.

Adobe PDF LogoA Review of Biofouling Controls for Enhanced In Situ Bioremediation of Groundwater
Environmental Security & Technology Certification Program (ESTCP), 62 pp, 2005

Biofouling is a common problem when nutrient-rich amendments for biostimulation are added to the subsurface through injection wells. This report reviews well rehabilitation and biofouling controls that are potentially relevant to enhanced in situ bioremediation applications and identifies promising biofouling controls for comparative field evaluation and validation.

Case Studies: TCE

Adobe PDF LogoBioenhanced In-Well Vapor Stripping (BEHIVS) to Treat Trichloroethylene
Strategic Environmental Research and Development Program (SERDP), 75 pp, 2003

In an August-December 2001 technology demonstration at Edwards AFB, in-well vapor stripping and in situ aerobic cometabolic bioremediation were combined to address a TCE source area without bringing contaminated groundwater to the surface.

Cometabolic Air Sparging at McClellan Air Force Base, OU A, Sacramento, CA
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

Two test plots were used for an 18-month demonstration of a cometabolic air sparging process: one control plot using air injection only and one active plot using air and propane to test cometabolic air sparging. In the saturated zone, concentrations of TCE and degradation products were reduced to near or below the MCLs after about 200 days of operation. Reductions in the active zone were attributed to propane degradation and cometabolism. Volatilization observed in the control zone contributed to contaminant removal. In the vadose zone, no contaminant cometabolism through propane degradation was observed after more than 500 days of operation, indicating that propane-degrading bacteria were not stimulated during the demonstration, possibly due to limited nitrogen in the subsurface.

Cometabolic Bioventing at Building 719, Dover Air Force Base, Dover Delaware
Federal Remediation Technologies Roundtable Cost & Performance Database, 2000

Maximum concentrations of chlorinated aliphatic hydrocarbons in soil found during site investigations were TCE at 250 mg/kg, TCA at 1,000 mg/kg, and DCE at 20 mg/kg, and estimated 26 pounds in the test plot. TCA made up ~70% of the total estimated contaminant mass. The soil in the area is sand with varying amounts of clay, silt and gravel. Soil permeability is 1.9x10-7 to 7.0x10-8 cm2. A blower and a mass flow controller were used to inject a mixture of air and propane (300 ppm in air) through three wells at a rate of 1 cfm. After 14 months of operation, concentrations of TCE, TCA, and DCE were reduced in the test area soil.

Adobe PDF LogoComparison of EHC, EOS, and Solid Potassium Permanganate Pilot Studies for Reducing Residual TCE Contaminant Mass
Marks, C.
E2S2: Environment, Energy Security and Sustainability Symposium and Exhibition, 9-12 May 2011, New Orleans, Louisiana. Presentation 12621, 30 slides, 2011

At the Defense Distribution Depot San Joaquin-Sharpe (DDJC-Sharpe) site, Lathrop, CA, three treatment technologies were evaluated for their potential to increase TCE mass removal in the saturated zone. Introduction of emulsified oil (EOS) in the North Balloon began in April 2008, injection of solid potassium permanganate in the South Balloon began in May 2008, and injection of a redox compound (EHC, complex organic carbon plus ZVI) in the Central Area began in August 2008. Where the amendment was able to contact the contaminant, all three amendments reduced TCE concentrations to <5 ug/L (the cleanup level). All three amendments continued to distribute/diffuse horizontally after injection and had secondary water quality impacts. Solid potassium permanganate was selected as the preferred amendment because it distributed/diffused significantly more in fine-grained soils than the other two amendments, destroyed TCE more quickly without formation of daughter products, and was cost effective because multiple injections were not necessary. The pilot study results also showed that hydraulic fracturing increased the distribution of the amendment in fine-grained soils when compared to gravity-fed injection wells. Additional information: Longer Abstract; DDJC-Sharpe 2009 5-Year ReviewAdobe PDF Logo.

Adobe PDF LogoDemonstration of Bioaugmentation at Kelly AFB, TX
B. Alleman, M. Place, and D. Major.
AFRL-ML-TY-TR-2004-4530, 155 pp, 2004

Describes an application of the KB-1 culture to remediate TCE contamination at Kelly AFB.

Demonstration of Bioaugmentation at Kelly AFB, Texas: ESTCP Cost And Performance Report
Environmental Security Technology Certification Program (ESTCP), 42 pp, 2007

After augmentation of the aquifer with KB-1 (a prepared culture of halorespiring bacteria) to address PCE, TCE, and their degradation products, complete dechlorination of PCE to ethene was observed.

Adobe PDF LogoDNAPL Bioremediation: RTDF. Innovative Technology Summary Report
U.S. DOE, Office of Environmental Management.
DOE/EM-0625, 29 pp, 2002

To address TCE, cDCE, and PCE contamination at Dover Air Force Base, three in situ bioremediation techniques were demonstrated between May 1996 and March 1998: cometabolic bioventing (for treatment of the vadose zone), intrinsic bioremediation (for treatment of the bulk of the plume), and accelerated anaerobic bioremediation (for treatment of more concentrated areas of a plume).

Adobe PDF LogoEdible Oil Barriers for Treatment of Chlorinated Solvent Contaminated Groundwater
M.T. Lieberman and R.C. Borden.
ESTCP Project ER-0221, 228 pp, 2009

A pilot test was conducted between 2003 and 2007 at Charleston Naval Weapons Station, SC, to evaluate the effectiveness of EOS®, a commercially available emulsified oil substrate, for enhancing the biodegradation of dissolved-phase chlorinated VOCs in groundwater and aquifer material in a treatment cell. The cell contained 4,000 cubic ft of contaminated aquifer material with up to 16,000 µg/kg TCE in soil and >20,000 µg/L TCE in groundwater. Phase I involved site characterization, baseline sampling, EOS injection, and monitoring for 28 months. Phase II involved a bench-scale treatability study, development and injection of a newly formulated pH-buffered substrate to overcome a pH problem, and an additional 11 months of monitoring to measure the effect of the second substrate. The buffered EOS raised the pH and alkalinity of the aquifer, which allowed the native dehalorespiring populations to re-initiate their metabolism of TCE and DCE and biodegrade TCE throughout the test cell. Over the entire 41-month monitoring period in Phases I and II, the total chlorinated VOC concentration decreased from 198 µM to 17 µM, a decline of 91%. See also the ESTCP Cost and Performance ReportAdobe PDF Logo.

Adobe PDF LogoEnhanced Attenuation of Unsaturated Chlorinated Solvent Source Zones Using Direct Hydrogen Delivery
Newell, C.J., A. Seyedabbasi, D.T. Adamson, T.M. McGuire, B. Looney, P.J. Evans, J.B. Hughes, M.A. Simon, and C.G. Coyle.
ESTCP Project ER-201027, 532 pp, 2013

Over a 6-month test period, a total of 830,000 standard cubic feet of gas—10% hydrogen, 79% nitrogen, 10% propane, and 1% carbon dioxide—was injected into a fine-grained vadose zone at a former missile silo site in Nebraska . The hydrogen gas was designed to stimulate biodegradation of TCE and its breakdown products that persisted after three years of SVE. Although the system was successful at converting TCE, a "cis-DCE stall" condition occurred. ESTCP Cost & Performance ReportAdobe PDF Logo

Adobe PDF LogoEnhanced In Situ Bioremediation. Innovative Technology Summary Report
U.S. DOE, Office of Environmental Management.
DOE/EM-0624, 29 pp, 2002

Covers a 1999-2000 demonstration to treat the TCE source area of a groundwater plume at the Test Area North site of DOE's Idaho National Engineering and Environmental Laboratory.

Enhanced In situ Biotransformation at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

Diluted (10 to 20%) raw blackstrap molasses was injected into impacted groundwater zones (upper and lower) to address TCE and its daughter products. Initial concentrations of TCE ranged from 26.5 to 5,300 µg/L. After 11 months, TCE concentrations appeared to have been reduced more in the upper water-bearing zone than in the lower water-bearing zone. In the upper zone, TCE concentrations fell more than 85% in two of the three downgradient monitoring wells, while remaining about the same in the third well. In the lower zone, TCE concentrations decreased ~15% in one of the three downgradient wells and increased in the other two wells.

Field Evaluation Report of Enhanced In Situ Bioremediation (ISB), Test Area North (TAN) Operable Unit (OU) 1-07B
K. Sorenson, J.P. Martin, and H. Bullock.
INEEL/EXT-2000-00258, Rev. 0, 149 pp, 2000

Discusses the complete degradation of PCE and TCE to ethene at Test Area North. Performance monitoring update.

Adobe PDF LogoFinal Report for the Enhanced Anaerobic Bioremediation Pilot Test, Bountiful/Woods Cross Superfund Site, Bountiful, Utah
Bureau of Reclamation, Denver, CO. 66 pp, 2006

This biostimulation/bioaugmentation pilot study to address TCE contamination involved a side-by-side comparison in 3 test cells of 3 different bioremediation substrates: sodium lactate, chitin, and emulsified soybean oil. Following the first round of substrate injection and sampling, all 3 test cells were inoculated with a commercially available dechlorinating culture containing Dehalococcoides ethenogenes. Based on the results of the pilot test, full-scale enhanced anaerobic bioremediation was selected for the site's 2006 Record of Decision. Emulsified oil is recommended as the electron donor.

Adobe PDF LogoImproving Effectiveness of Bioremediation at DNAPL Source Zone Sites by Applying Partitioning Electron Donors (PEDS)
Lebron, C.A ., D. Major, M. McMaster, and C. Repta.
ESTCP Project ER-200716, CR-NAVFAC-EXWC-EV-1402, 3,859 pp, 2014

Partitioning electron donors (PEDs) are water-soluble electron donors that partition directly into a target DNAPL to effect enhanced in situ bioremediation. A PED technology field demonstration was conducted at a TCE source zone at NASA Launch Complex 34 using n-butyl acetate (nBA), a colorless liquid that volatilizes to form dense vapors that have the potential to form an explosive mixture with air. Introduced to the source area using direct-push injection equipment, nBA was able to promote biodegradation and achieved sustained production of dechlorination products, even in the presence of co-contaminant 1,1,2-trichloro-1,2,2-trifluoroethane (CFC113). This project showed that nBA can (1) achieve high rates of biologically enhanced DNAPL dissolution; (2) be easily and effectively delivered; and (3) sustain donor supply at an effective concentration at the DNAPL:water interface to promote the growth and activity of the dechlorinating biomass. [Note: See the first 112 pages of the PDF file for the main report; the subsequent appendices contain lab forms, boring logs, and other field data.] Additional information: ESTCP Cost and Performance ReportAdobe PDF Logo.

Adobe PDF LogoIn Situ Bioremediation of Chlorinated Solvent Source Areas with Enhanced Mass Transfer
T. Macbeth, and K. Sorenson.
Environmental Security Technology Certification Program (ESTCP), Project ER-0218, 396 pp, 2008

A demonstration of enhanced mass transfer of chloroethenes from DNAPL to groundwater during in situ bioremediation of TCE was conducted at the Fort Lewis Logistics Center East Gate Disposal Yard (EGDY) using the Bioavailability Enhancement Technology?, or B.E.T.(tm). For the first time at the field scale, this demonstration provided rigorous documentation of the electron donor (whey) concentration-dependence of enhanced mass transfer of chlorinated solvents in a source area. In 2 hydraulically isolated treatment cells, each consisting of a network of monitoring wells, an injection well, and an extraction well, anaerobic reductive dechlorination occurred concurrently with enhanced mass transfer and resulted in rapid source strength reduction. The rapid effect on downgradient contaminant flux observed at the Ft. Lewis site might be a best-case scenario owing to the high ambient groundwater flow rates. See also the ESTCP Cost and Performance ReportAdobe PDF Logo.

In Situ Bioremediation Using HRC® at a Former Industrial Property, San Jose, CA
Federal Remediation Technologies Roundtable Cost & Performance Database, 2004

The 4.1 acre property, the site of various former manufacturing concerns, is occupied by a 76,000 sq foot building currently used for light industrial retail. Site investigations conducted in the late 1980s showed the presence of VOCs in the subsurface, with TCE concentrations as high as 5,000 µg/L in groundwater and 10,000 µg/kg in soil. After the first injection of HRC® in May 2000, TCE concentrations decreased, with corresponding increase in degradation products cis-1,2-DCE and VC. After the second injection in November 2001, TCE concentrations continued to decrease, concentrations of cis-1,2-DCE and VC decreased, and concentrations of degradation product ethene increased. As of July 2003, TCE concentrations were below cleanup goals in selected wells. While concentrations of cis-1,2-DCE and VC continued to decrease, they remained above the cleanup goals in most of the selected wells. Currently, groundwater monitoring and natural attenuation monitoring are being performed on a semiannual basis at the site.

Adobe PDF LogoIn-Situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: ESTCP Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP), 93 pp, 2007

Describes the treatment of TCE plumes by substrate addition at Hanscom and Vandenberg Air Force bases.

Adobe PDF LogoIn-Situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: Hanscom Air Force Base
C.C. Lutes, V. D'Amato, A. Frizzell, M. Hansen, G. Gordon, P. Palmer, and S. Suthersan.
Environmental Security Technology Certification Program (ESTCP), 431 pp, 2003

The active treatment phase of the demonstration took place from October 2000 to October 2002, during which time 47 injections conducted in a single injection well delivered 1,250 gallons of raw blackstrap molasses, 11,250 gallons of dilution water, 7,575 gallons of push water, and 4,732 grams of potassium bromide. Monitoring was conducted during the demonstration to gauge technology effectiveness, describe changes in biogeochemical conditions, and gather process monitoring feedback.

Adobe PDF LogoIn-Situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: Vandenberg Air Force Base
C.C. Lutes, A. Frizzell, B. Molnaa, and P. Palmer.
Environmental Security Technology Certification Program (ESTCP). 335 pp, 2004.

Documents an evaluation of the efficacy of the in situ reactive zone/enhanced reductive dechlorination (IRZ/ERD) technology in removing TCE from impacted groundwater in a range of geologic conditions and TCE concentrations. Active molasses-based treatment from February 2001 to April 2003 provided an opportunity to evaluate IRZ at a site that was initially highly aerobic, with minimal evidence of natural attenuation of TCE.

Adobe PDF LogoA Low-Cost, Passive Approach for Bacterial Growth and Distribution for Large-Scale Implementation of Bioaugmentation
Trotsky, J., R.A. Wymore, M.R. Lamar, and K.S. Sorenson.
ESTCP Project ER-200513, TR-2354-ENV, 585 pp, 2010

The relative pros and cons of active recirculation and low-cost, passive inject-and-drift strategies for large-scale bioaugmentation of TCE in groundwater were evaluated in a side-by-side comparison at the Seal Beach Naval Weapons Station, Seal Beach Site 70, CA. The active and passive approaches were compared in a full-scale TCE source area application. Electron donor was added weekly for the active cell and monthly for the passive cell. After several months of pre-conditioning, a commercially available culture was added. Overall, bacterial growth and dechlorination performance was similar using both approaches, but the active system was more costly. ESTCP Cost and Performance ReportAdobe PDF Logo

Adobe PDF LogoOperation and Analysis of the BEHIVS System at Edwards Air Force Base
P.L. McCarty, S.M. Gorelick, M.N. Goltz, G.D. Hopkins, and F.-J. Eisenberg.
Strategic Environmental Research and Development Program (SERDP), 109 pp, 2003

Summarizes the results of operating a bioenhanced in-well vapor stripping (BEHIVS) system at Edwards AFB in 2001, numerical modeling analysis of the results, study conclusions, and recommendations for application of the BEHIVS system at other sites.

Adobe PDF LogoPerformance of Full-Scale Enhanced Reductive Dechlorination in Clay Till
Damgaard, I. , P.L. Bjerg, C.S. Jacobsen, A. Tsitonaki, H. Kerrn-Jespersen, and M.M. Broholm.
Ground Water Monitoring & Remediation 33(1):48-61(2013)

Enhanced reductive dechlorination was implemented by direct-push injection of molasses and dechlorinating bacteria at a low-permeability clay till site contaminated with chlorinated ethenes (Gl. Kongevej, Denmark ). After 4 years of remediation, the formation of degradation products, the presence of Dehalococcoides spp., and the isotope fractionation of TCE, cis-DCE, and VC demonstrated the degradation of chlorinated ethenes in the clay till matrix as well as in sand lenses, sand stringers, and fractures. Bioactive sections of up to 1.8 m had developed in the clay till matrix, while sections where degradation was restricted to narrow zones around sand lenses and stringers were also observed. An average mass reduction of 24% was estimated after 4 years of remediation. Model simulation scenarios indicate that a mass reduction of 85% can be obtained within ~50 years without further increase in the narrow reaction zones if no donor limitations occur at the site. Additional information: I. Damgaard Ph.D. thesisAdobe PDF Logo (2012); Broholm et al.Adobe PDF Logo (2012); Design Tool

Project SABRE: Source Area BioRemediation
CL:AIRE (Contaminated Land: Applications in Real Environments), London, UK. SABRE Bulletins 1-6, Sep 2010

Project SABRE began in October 2004 and ran through 2009 at a former chemical manufacturing plant in the East Midlands. A multidisciplinary team from the UK, USA, and Canada undertook the 5-year collaborative project to demonstrate that in situ enhanced anaerobic bioremediation can result in effective treatment of chlorinated solvent DNAPL source areas—in this case, TCE. The project team also sought to improve related site investigation tools and understanding of subsurface processes. Enhanced bioremediation was implemented through introduction of DNAPL-partitioning soya oil emulsion (SRS(tm), a commercial product provided by Terra Systems Inc.) to the source zone as a source of electron donor at the DNAPL:water interface. As one of the most highly instrumented field-scale groundwater test facilities constructed anywhere in the world, the SABRE test cell provided effective containment of groundwater in the sandy gravel aquifer enclosed within the cell, which enabled the field trials to be conducted with a constrained flow field, controlled residence times, and relatively accurate quantification of mass fluxes.

Pump and Treat and In Situ Bioremediation of Contaminated Groundwater at the French Ltd. Superfund Site, Crosby, Texas
Federal Remediation Technologies Roundtable Cost & Performance Database, 1998

The French Limited site was used for sand mining in the 1960s and 1970s. During the period from 1966 through 1971, the site was permitted to accept industrial waste material for disposal in a 7-acre lagoon created from an open sand pit. About 80 million gallons of waste material were disposed of in the main waste lagoon. Source control was achieved by installation of sheet-pile walls around lagoon and DNAPL source areas. Active remediation was conducted at the site from January 1992 through December 1995 by groundwater extraction and above-ground treatment, enhanced aquifer flushing through pressure injection of clean water, and accelerated in situ bioremediation through the addition of oxygen, phosphorus, and nitrate. As of December 1995, active pumping was stopped and natural attenuation has been used to reduce remaining concentrations of contaminants.

Adobe PDF LogoRemedial Action Completion Report (CDRL A001B) and Preliminary Closeout Report, Former Air Force Plant PJKS, Waterton Canyon, Colorado
Air Force Center for Engineering and the Environment, 44 pp, 2013

A pilot study conducted at PJKS in 2004-2005 to evaluate the effectiveness of in situ anaerobic reductive dechlorination (ARD) of TCE and NDMA in bedrock source areas showed a decline in TCE contamination, which in 2006 led to the expansion of an interim corrective measure to stimulate ARD in the D-1 area groundwater plume. Horizontal and vertical injection wells delivered sodium lactate, emulsified edible oil (EEO), nutrients, and Dehalococcoides (dhc) to the Fountain Formation aquifer. In 2008, two full-scale biobarriers were constructed via injection of EEO, sodium lactate, and dhc into direct-push boreholes to target the alluvial transition groundwater areas, provide a barrier to plume migration, and further deplete TCE contamination in the downgradient plume. A technical impracticability waiver is recorded in the ROD for NDMA in the crystalline bedrock due to geological and technological limitations, although the VOCs in the bedrock are expected to meet MCLs. Additional information: PJKS EE/CA (2005)Adobe PDF Logo; Focused Feasibility Study (2010)Adobe PDF Logo; Case Study Slides (2012)Adobe PDF Logo

Abstracts: TCE

The Effect of Concentrated Electron Donors on the Solubility of Trichloroethene
E. Hood, D. Major, and G. Driedger.
Ground Water Monitoring & Remediation, Vol 27 No 4, p 93-98, 2007

Although recent vendor claims suggest that the addition of highly concentrated electron donor solutions to increase the aqueous solubility of TCE during enhanced in situ bioremediation is a significant mechanism of contaminant mass removal, the results of experimental measurements of the solubility of TCE in aqueous solution with 8 typical electron donors suggest that due to the small changes in TCE solubility in comparison to the high electron donor concentrations employed, it is difficult to envision circumstances justifying the use of a high electron donor concentration to enhance TCE solubility as part of a bioremediation strategy, though the use of more concentrated (e.g., 50 to 95%) ethanol solutions would be appropriate for cosolvent flooding.