Anaerobic degradation of paper mill sludge

The effect of pH adjustment and surfactant addition on the anaerobic degradation of sludge from a pulp and paper mill waste treatment plant was monitored by COD (Chemical Oxygen Demand) and EOX (Extractable Organic Halogen) analysis. COD decreased by 29–64% and EOX by 22–50%, in all treatments (including control, non-adjusted, sludges). Adjusting the initial pH to 7.0 with sodium bicarbonate, but not with potassium hydroxide, accelerated degradation. Maximum decreases in dry weight, COD and EOX, compared to the control, were seen in sludges receiving bicarbonate; after 5 months the reductions were 60% (COD) and 50% (EOX). The results indicate that the use of bicarbonate to adjust pH could be advantageous in anaerobic treatment of organochloride-containing residues.