Effects of chemical spills on activated sludge treatment performance in pulp and paper mills

The aim of this research was to study the effects of chemical spills on act ivated sludge metabolic activity and settleability. On-site, laboratory-sca le tests were carried out at three pulp and paper mill activated sludge pla nts. Oxygen uptake rate (OUR) and dissolved organic carbon (DOC) removal we re used for monitoring of metabolic inhibition. The effects of chemicals on 30-min settled sludge volume were studied. Accidental release reports from five pulp and paper mills were analysed. Thirty-four chemicals were selected to the laboratory tests. Of the tested chemicals 2 biocides,monochloro acetic acid, soft soap and turpentine inhib ited the OUR of the sludge and thus, had an acute toxic effect on the activ ated sludge. The biocides and disperging agent reduced DOC removal. Alumini um sulphate and optical brightener had a negative effect on sludge settleab ility and thus, they may cause losses of activated sludge from treatment pl ant. In conclusion, maximum possible spill of the five chemicals may reduce the performance of the activated sludge. (C) 1999 Published by Elsevier Sc ience Ltd on behalf of the IAWQ. All rights reserved.