Intrinsic in situ anaerobic biodegradation of chlorinated solvents at an industrial landfill

The DuPont Necco Park Landfill in Niagara Falls, New York, is contaminated with numerous chlorinated solvents at concentrations of up to hundreds of mg/L in the groundwater. An extensive monitoring program was conducted to determine if intrinsic anaerobic biodegradation was occurring at the site, to determine what might limit this activity, and to characterize this activity with depth and distance away from the landfill. It was determined that anaerobic microbial activity was occurring in all zones, based upon the presence of intermediate products of the breakdown of the chlorinated solvents and the presence of final metabolic end products such as ethene and ethane. Aerobic, iron-reducing, manganese-reducing, sulfate-reducing, and methanogenic redox conditions were identified at the site. High levels of nitrogen and biodegradable organic compounds were present in most areas to support cometabolic anaerobic microbial activity against the chlorinated solvents. Intrinsic biodegradation is clearly evident and is effective in reducing the concentrations of chlorinated organic in the groundwater at the site. Groundwater modeling efforts during development of a site conceptual model indicated that microbial degradation was necessary to account for the downgradient reduction of chlorinated volatile organic compounds as compared to chloride, a conservative indicator parameter.