ABSTRACT
A large-scale field evaluation of enhanced biodegradation of chloroethenes using lactate as an electron donor was recently performed at Test Area North of the Idaho National Engineering and Environmental Laboratory. A residual source of chloroethenes, primarily trichloroethene, is present in the fractured basalt aquifer at the site, from about 60 to 120 m below land surface. The residual source area is approximately 60 m in diameter. Dechlorination was strongly correlated with elevated chemical oxygen demand measurements, and the extent of dechlorination was strongly correlated with terminal electron acceptor processes. The onset of dechlorination coincided with the onset of sulfate reduction, and significant conversion to ethene was only observed in the presence of methanogenesis. After less than 1 year, the redox conditions were successfully manipulated to achieve complete dechlorination in this complex hydrogeologic setting.
