A MECHANICAL PRETREATMENT OF WASTE ACTIVATED-SLUDGE FOR IMPROVEMENT OF ANAEROBIC-DIGESTION SYSTEM

This study evaluated the effectiveness of sewage pretreatment as it af fected the subsequent anaerobic digestion of waste activated sludge (W AS). The key to this sludge pretreatment process was that microorganis m cells within WAS were ruptured by mechanical jet and smash under pre ssurized conditions, 5-50 bar pressure. Cell rupture was estimated by soluble protein concentration (SPC) because the cytoplasm of microorga nisms is mainly composed of protein. The SPC in the WAS varied signifi cantly before and after pretreatment. In particular, cell rupture incr eased from 6% to 43% with the increase of the pretreated pressure (5-3 0bar), volatile solids concentration and thickening time of WAS. In th e WAS pretreatment with long-thickening time (12h < thickening time le ss than or equal to 48h), cell rupture was monitored 5-10 % higher tha n short-thickening time (Oh <thickening time less than or equal to 12h ). Generally, it was observed that higher anaerobic digestion efficien cies of WAS could be obtained according to the increase of microorgani sm cell rupture through mechanical pretreatment of WAS. (C) 1997 IAWQ. Published by Elsevier Science Ltd.