EFFECTS OF POLYCHLORINATED BIPHENYL CONGENER CONCENTRATION AND SEDIMENT SUPPLEMENTATION ON RATES OF METHANOGENESIS AND 2,3,6-TRICHLOROBIPHENYL DECHLORINATION IN AN ANAEROBIC ENRICHMENT

We have employed a method of enrichment that allows us to significantl y increase the rate of reductive polychlorinated biphenyl (PCB) dechlo rination. This method shortens the time required to investigate the ef fects that culture conditions have on dechlorination and provides an e stimate of the potential activity of the PCB-dechlorinating anaerobes. The periodic supplementation of sterile sediment and PCB produced an enhanced, measurable, and sustained rate of dechlorination. We observe d volumetric rates of the dechlorination of 2,3,6-trichlorobiphenyl (2 ,3,6-CB) to 2,6-dichlorobiphenyl (2,6-CB) of more than 300 mumol liter -1 day-1 when the cultures were supplemented daily. A calculation of t his activity that is based on an estimate of the number of dechlorinat ing anaerobes present indicates that 1.13 pmol of 2,3,6-CB was dechlor inated to 2,6-CB day-1 bacterial cell-1. This rate is similar to that of the reductive dechlorination of 3-chlorobenzoate by Desulfomonile t iedjei. Methanogenesis declined from 585.3 to 125.9 mumol of CH4 liter -1 day-1, while dechlorination increased from 8.2 to 346.0 mumol of 2, 3,6-CB dechlorinated to 2,6-CB liter-1 day-1.