BIOSORPTION OF CHLOROPHENOLS TO ANAEROBIC GRANULAR SLUDGE

The sorption of chlorophenols by anaerobic sludge granules was studied in order to more completely understand the fate of chlorophenols and their degradation products in upflow anaerobic sludge blanket reactors. Sorption isotherms were determined for pentachlorophenol and most isomers of tri-, di- and monochlorophenols, and the data were fitted to the Freundlich equation. Sorption by the sludge granules was considerable. Most, but not all, chlorophenols had linear sorption isotherms, which were defined by simple distribution coefficients. Those distribution coefficients were only weakly correlated to octanol-water partition coefficients, and there were no obvious relationships between sorption and numbers or positions of chlorine substituents. Sorption of two chlorophenols was highly reversible, but it was not for a third chlorophenol tested. Pentachlorophenol was more strongly sorbed than the lesser-chlorinated phenols, and pentachlorophenol sorption by sludge granules was weaker than its previously reported sorption by other biological materials. The Freundlich model, with empirically determined constants from this study, described the partitioning behaviour of chlorophenols in anaerobic sludge blanket reactors reasonably well.