Assessment of the ability of sludge to degrade PCP under anaerobic conditions

The capacity of sludge from different sources to degrade pentachlorophenol (PCP) was evaluated. Three 2.5 liter reactors (R-1, R-2, and R-3) were inoculated with different anaerobic sludges, semi continuously fed and maintained in orbital motion at 30 +/- 1 degrees C. R-1 was inoculated with aerobic sludge and river sediment collected downstream from a pulp and paper plant. R-2 received sludge from an anaerobic reactor treating effluents from a paper recycling plant and R-3 received anaerobic sludge from a biodigestor treating industrial and domestic effluents. The sludges were first acclimatized to a culture medium generally recommended for organochloride anaerobic degradation studies. The reactors were then subjected to increasing concentrations of PCP from 0.05 to 10.0 mg.l(-1). PCP degradation and metabolite formation were monitored using gas chromatography, and the effects of PCP on the anaerobic process were verified by monitoring pH, volatile fatty acids, alkalinity, total suspended solids, and chemical oxygen demand. It was found that PCP did not affect reactor performance. All the sludges displayed the best PCP degradation capacity at a concentration of 0.2 mg.l(-1), producing fewer chlorinated metabolites than when higher PCP concentrations were applied. R-1 consistently produced fewer chlorinated metabolites, confirming the hypothesis that pre exposure to chlorinated compounds improves the sludge's capacity to degrade PCP.