Intrinsic and accelerated anaerobic biodegradation of perchloroethylene in groundwater

The DuPont Niagara Falls Plant is located in a heavily industrialized area of Niagara Falls, New York, adjacent to the Niagara River. The plant has been in continuous operation since 1898 and manufactured various organic and inorganic chemicals. Chlorinated solvents were produced from 1930 to 1975 at the plant. Numerous hydrogeologic investigations have described the subsurface hydrogeology and indicated that the groundwater underlying the plant was impacted by a variety of chlorinated aliphatic hydrocarbons in a wide range of concentrations. DuPont initiated in-field evaluations to determine whether biological reductive anaerobic dechlorination was occurring naturally and, if so, whether such dechlorination could be enhanced in situ. A field program was subsequently implemented could be enhanced in situ. A field program was subsequently implemented in a preselected area of the plant through use of an in situ borehole bioreactor to attempt to stimulate indigenous biological reductive dechlorination of chlorinated aliphatics by the addition of yeast extract (substrate) and sulfate (electron acceptor). At this location, a very active microbial population developed, which reduced the in situ concentrations of chlorinated aliphatic compounds by more than 94%, but did not increase the typical biological degradation products. This may have been due to an alternative biologicalmore » degradation pathway or to very rapid biological kinetics. Efforts to elucidate this mechanism have been initiated under a separate laboratory program.« less