Microbial Degradation of Chloroethenes in Ground Water Systems

The chloroethenes, tetrachloroethene (PCE) and trichloroethene (TCE), are among the most common contaminants detected in ground water systems. As recently as 1980, the consensus was that chloroethene compounds were not significantly biodegradable in ground-water. Consequently, efforts to remediate chloroethene contaminated ground water were limited to largely unsuccessful pump and treat attempts. Subsequent investigation revealed that, under reducing conditions, aquifer microorganisms can reductively dechlorinate PCE and TCE to the less chlorinated daughter products, dichloroethene (DCE) and vinyl chloride (VC). Although recent laboratory studies conducted with halorespiring microorganisms suggest that complete reduction to ethene is possible, in the majority of ground-water systems reductive dechlorination apparently stops at DCE or VC. However, a number of recent USGS investigations conducted with aquifer and stream bed sediments have demonstrated that microbial oxidation of these reduced daughter products can be significant under anaerobic redox conditions. The combination of reductive dechlorination of PCE and TCE under anaerobic conditions followed by anaerobic microbial oxidation of DCE and VC provides a possible microbial pathway for complete degradation of chloroethene contaminants in ground-water systems. Thus making monitored natural attenuation a potential alternative to pump and treat remediation for many sites contaminated with chloroethenes.

Since 1995, a team of USGS researchers have been studying the potential for anaerobic microbial oxidation of chlorinated ethenes.

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Overview of Research Accomplishments

• Microbial Oxidation of Vinyl Chloride Under Iron-Reducing Conditions
• Effect of Terminal Electron Accepting Conditions on Chloroethene Oxidation
• Anaerobic Oxidation of Vinyl Chloride Under Humic-Acids-Reducing Conditions
• Role of Acetogens in Anaerobic Oxidation of VInyl Chloride

Project Remediation Related Activities

• RDX Biodegradation Assessment, Naval Submarine Base Bangor, Washington
• Chlorinated Benzene Plume Source Area Containment Test (Oxygen-Release Compound Injection)
• Solvent Plume Source Removal Test (Fenton's Reagent)

Related Research

• Aerobic Microbial Mineralization of Dichloroethene as the Sole Carbon Substrate

More Information

• Project Bibliography
• Project Photo Gallery
• Research Team
• For additional information please send e-mail to Paul Bradley at

Other Chlorinated Solvent Remediation Related Activities

• Can Trees Clean Up Ground Water? Phytoremediation of Trichloroethene-Contaminated Ground Water at Air Force Plant 4, Fort Worth, Texas
• Phytoremediation in the Desert?
• Natural Attenuation of Wood Preservatives in Ground Water

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