INFLUENCE OF METHYLENE CHLORIDE ON BIODEGRADATION OF OTHER CHLORINATED COMPOUNDS

摘要

Methylene chloride (MC) appears to have promoted biodegradation of other chlorinated volatile organic compounds (CVOCs) in groundwater at an industrial site. The other major contaminants included tetrachloroethene (PCE), trichloroethene (TCE), trichloroethane (TCA) and their daughter products, dichloroethane (DCA) and dichloroethene (DCE). Seasonal changes in groundwater recharge cycles and intermittent operation of a dual phase extraction (DPE) system created sequential aerobic and anaerobic conditions, as measured by seasonal changes in dissolved oxygen (DO) and oxidation/reduction potential. Based on spatial correlation of MC, organic acids, and DO, MC is acting as an electron donor and enhancing the biodegradation of other CVOCs under seasonally alternating aerobic/anaerobic conditions at the site. Cometabolic processes may be the primary mechanism driving biodegradation as a result of MC acetogenesis, formate production, and the presence of methane. The presence and degradation of MC in the source zone appears to contribute to the overall stability of CVOC plume.