THE BIODEGRADATION OF CHLORINATED ALIPHATIC ALIPHATIC COMPOUNDS BY METHANE-UTILIZING BACTERIA: MECHANISM AND PRODUCTS

LOW MOLECULAR WEIGHT CHLORINATED HYDROCARBONS ARE WIDESPREADENVIRONMENTAL CONTAMINANTS AND ARE OF CONCERN BECAUSE OF THEIR TOXIC AND CARCINOGENIC PROPERTIES. THEY ARE PERSISTENT IN SOILS AND GROUNDWATER, RESIST DEGRADATION IN BIOLOGICAL WASTEWATER TREATMENT SYSTEMS, AND ARE EXPENSIVE TO REMOVE FROM WATER BY PHYSICAL/CHEMICAL PROCESSES. WE HAVE ISOLATED A BACTERIUM WHICH GROWS BY OXIDIZING METHANE (A METHANOTROPH) AND WHICH CAN ALSO OXIDIZE AND DEGRADE VINYL CHLORIDE, VINYLIDENE CHLORIDE, ALL DICHLOROETHYLENES, AND TRICHLOROETHYLENE, PLUS TWO CHLORINATED ETHANES AND TWO CHLOROMETHANES. THIS DISCOVERY HAS SIGNIFICANT POTENTIAL FOR APPLICATIONS IN THE FIELD OF GROUNDWATER AND WASTEWATER TREATMENT. OUR PRELIMINARY EXPERIMENTS WITH 14C-TRICHLOROETHYLENE BIODEGRATDATION DEMONSTRATED THAT AT LEAST 60% OF THE 14C COULD BE RECOVERED AS 14C02 AND 14C-BIOMASS. BASED ON REPORTED REACTION MECHANISMS FOR THE OXIDATION OF CHLORINATED ETHENES IN MAMMALIAN SYSTEMS, WE HAVE DETERMINEDTHAT THE INITIAL OXIDATION PRODUCTS SHOULD BE DEGRADABLE BY BACTERIA. WE PROPOSE TO CARRY OUT EXTENSIVE CHEMICAL ANALYSIS OF THE PRODUCTS OF METHANOTROPHIC DEGRADATION OF THE SELECTED CONTAMINANTS IN ORDER TO DEMONSTRATE FOR EACH ONE THAT NO TOXIC PRODUCTS ARE FORMED. WE ALSO PROPOSE TO OPERATE A LABORATORY-SCALE TREATMENT COLUMN EMPLOYING OUR METHANOTROPHIC ISOLATE AND TO OPTIMIZE CONDITIONS FOR THE REMOVAL OF CHLORINATED ALIPHATICS FROM CONTAMINATED WATER.