Reductive dechlorination of nonachlorobiphenyls and selected octachlorobiphenyls by microbial enrichment cultures

The anaerobic dechlorination of four octachlorobiphenyls [2,3,4,5,6,2’,3’,4’-octachlorobiphenyl (23456-234-octaCB), 2345-2346-octaCB, 2345-2356-octaCB, and 23456-245-octaCB] and three nonachlorobiphenyls [23456-2345-nonaCB, 23456-2346-nonaCB, and 23456-2356-nonaCB] was investigated. The single congeners were added to two different previously studied microbial enrichment cultures, and the cultures were monitored over a period of 16 weeks. All seven congeners were reductively dechlorinated. The predominant dechlorination patterns for all congeners, in both cultures, showed meta-dechlorination of doubly flanked m-chlorines followed by meta-dechlorination of singly flanked m-chlorines. Some ortho- and para-dechlorination was also observed. All congeners had an initial concentration of 50 ppm in soil, and the extent of dechlorination over the 16-week period varied widely, from 38% dechlorination of congener 23456-245-octaCB to only 1.4% removal of congener 23456-2345-nonaCB.