METABOLISM AND KINETICS OF PENTACHLOROPHENOL TRANSFORMATION IN ANAEROBIC GRANULAR SLUDGE

Granular sludge from an upflow anaerobic sludge blanket (UASB) reactor operated for 18 months on a mineral medium containing pentachlorophenol (PCP), phenol, and glucose was studied. Under methanogenic conditions PCP was dechlorinated to lower chlorinated phenols, primarily di-, and monochlorophenols. The initial dechlorination of PCP and the removal of the intermediate 3,5-dichlorophenol (3,5-DCP), seemed to be rate-limiting. Addition of sulphate was slightly inhibitory for PCP transformation in t e presence of glucose but had little or no effect on dechlorination in vials without glucose. Nitrate was strongly inhibitory. The consortium had a high affinity for PCP, with an apparent half-saturation constant (K(s)) value of 580-mu-g/l. Addition of various easily degradable carbon compounds including acetate, butyrate, formate, hydrogen/carbon dioxide, ethanol, and glucose together with extra PCP, to cultures already dechlorinating PCP showed that only glucose had a stimulatory effect on the dechlorination rate. Counts of bacteria from a sample of disintegrated granular sludge showed that the number of dechlorinating organisms was low compared to the numbers of glucose degraders and methanogens.