In situ biological treatment of TCE‐impacted soil and groundwater: Demonstration results

Abstract

AbstractAn in situ biological treatment technique designed to destroy trichloroethylene (TCE) was demonstrated at field scale at a manufacturing facility in the Midwest. Air and methane were injected into the contaminated groundwater through a vertical sparge well, while air was extracted from the vadose zone though a well screened in the unsaturated zone. A mobile demonstration test trailer housing air injection compressor, soil venting blower, and methane injection equipment was used to allow rapid equipment deployment, setup, and demobilization. Air and methane act to stimulate indigenous microorganisms to degrade TCE and dichloroethylene (DCE) via aerobic cometabolism. Toxic degradation products, such as vinyl chloride, are not generated by methanotrophic cometabolism.The demonstration was conducted over a three‐month time period, with groundwater and soil gas monitored weekly for several chemical and microbiological parameters. The test successfully stimulated the methanotroph population to increase over one order of magnitude and soil gas carbon dioxide (a by‐product of biodegradation) concentrations to increase when methane was injected into the aquifer. In addition, groundwater volatile organic compounds were reduced by 60 to 80 percent in the groundwater monitoring wells that were sampled.