REDUCTIVE DECHLORINATION OF AROCLOR 1254 BY MARINE SEDIMENT CULTURES

Reductive dechlorination of polychlorinated biphenyls (PCBs) was studi ed by methanogenic and sulfate-amended laboratory cultures enriched fr om marine sediments (Puget Sound, WA) in sea-salts media. One sulfate- amended and one methanogenic culture were incubated at a hydraulic ret ention time of 50 days and fed chitin, sodium benzoate, sodium acetate , and a mixture of four PCB congeners (2,3,3',5-tetrachlorobiphenyl, 2 ,2',4,5,6'-pentachlorobiphenyl, 2,3',4,5',6-pentachlorobiphenyl, and 2 ,2',4,4',5,5'-hexachlorobiphenyl), slowly increasing the concentration s to 6-9 mg/L over 17 months. In these cultures, no dehalogenation of the four congeners was observed. Two other cultures were batch fed Aro clor 1254 at a concentration of 100 mg/L; chitin was used as the PCB c arrier and the sole carbon and electron source. Chitin was readily min eralized both under methanogenic and sulfidogenic conditions. Aroclor 1254 was dechlorinated both in the presence and absence of sulfate. Th e dechlorinations started in both cultures after 4 months of incubatio n. Under both culturing conditions, 14-15% meta and 9-10% of para chlo rines were removed over a period of 1 year with the accumulation of ma inly tetrachlorobiphenyls; the extent of dechlorination was 7-8%.