Dechlorination of pentachlorophenol in anaerobic sewage sludge

Dechlorination of pentachlorophenol (PCP) in municipal sewage sludge by a chlorophenols (CPs)-adapted consortium was investigated. Results of a batch experiment showed no significant differences in PCP dechlorination following treatment with inoculum at densities ranging from 10% to 50%, but a significant delay following treatment with inoculum at 5% density. Results also show that the higher the PCP concentration, the slower the dechlorination rate. PCP dechlorination was not significantly altered by the addition of acetate, lactate, pyruvate, vitamin B-12 or. manganese dioxide. Results from a bioreactor experiment show optimal pH for dechlorination at 7.0 and optimal total solid concentration at 10 g/L. Dechlorination rates were also found to decrease significantly at higher agitation speeds. Finally. it was found that methanogenic conditions enhanced PCP dechlorination, but denitrifying and sulfidogenic conditions inhibited the dechlorination process. (C) 1997 Elsevier Science Ltd.