DECHLORINATION OF POLYCHLORINATED BIPHENYL CONGENERS BY AN ANAEROBIC MICROBIAL CONSORTIUM

An anaerobic methanogenic microbial consortium, developed in a granula r form, exhibited extensive dechlorination of defined polychlorinated biphenyl (PCB) congeners. A 2,3,4,5,6-pentachlorobiphenyl was dechlori nated to biphenyl via 2,3,4,6-tetrachlorobiphenyl, 2,4,6-trichlorobiph enyl, 2,4-dichlorobiphenyl and 2-chlorobiphenyl (CB). Removal of chlor ine atoms from all three positions of the biphenyl ring, i.e., ortho, meta and para, was observed during this reductive dechlorination proce ss. Biphenyl was identified as one of the end-products of the reductiv e dechlorination by GC-MS. After 20 weeks, the concentrations of the d echlorination products 2,4,6-CB, 2,4-CB, 2-CB and biphenyl were 8.1, 4 1.2, 3.0 and 47.8 mu M respectively, from an initial 105 mu M 2,3,4,5, 6-CB. The extent and pattern of the dechlorination were further confir med by the dechlorination of lightly chlorinated congeners including 2 -CB, 3-CB, 4-CB, 2,4-CB and 2,6-CB individually. This study indicates that the dechlorination of 2,3,4,5,6-CB to biphenyl is due to ortho, m eta and para dechlorination by this anaerobic microbial consortium.