AbstractTrichloroethylene (TCE) is one of the most widely used chlorinated solvents; it is also a common groundwater contaminant. TCE–contaminated groundwater is presently treated by transferring the solvent either to a solid (carbon adsorption) or to the atmosphere (air stripping). Biological treatment of the contaminated water is an alternative that causes complete destruction of the solvent. When performed within the aquifer it is termed in situ biotreatment. A specific strain of bacteria (G4) has been isolated that degrades TCE enzymatically. The process has been extensively tested in the laboratory and confirmed in a field pilot test. The pilot test involved the injection of a clean, oxygenated water stream directly into the TCE plume. Nutrients and G4 were added to the injection stream and TCE concentrations were measured up–and downgradient of the injection well. A decline in TCE levels was observed eight hours after injection and continued for the following ten days. TCE concentrations were reduced from a high of 3,000 ppb to a mean value of 78 ppb during a 20 day per
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