ESTIMATION OF ANAEROBIC BIODEGRADATION RATES FOR TOXIC ORGANIC-COMPOUNDS IN MUNICIPAL SLUDGE-DIGESTION

The removal of selected toxic compounds during anaerobic digestion of municipal sludge was investigated at pilot scale. In primary digestion , isoquinoline, p-cresol, 4-chlorophenol, 2,4,5-chlorophe nol, diethyl phthalate, di-n-butyl phthalate and butylbenzyl phthalate were remove d at efficiencies greater than 90%. Bis-2-ethylhexyl phthalate, o-cres ol and 2,5-dichlorophenol were removed at efficiencies of between 55 a nd 65%. Greater than 60% of the toxic compounds entering secondary dig estion were degraded. The anaerobic biomass appeared to acclimate to b iodegrade the chlorophenolic compounds during the experimental period. A dynamic model, developed to predict the fate of toxics during prima ry sludge digestion, was calibrated with data from the experiment. Bio degradation rate coefficients only could be estimated due to statistic al redundancy of the sorption partitioning parameter during the non-li near regression. The sorption partition coefficients were estimated fr om literature octanol-water partitioning coefficients.