Effects on anaerobic digestion of sewage sludge pretreatment

This research investigates the effect of sludge pretreatment on the anaerobic digestion of waste-activated sludge (WAS). In the key of this sludge pretreatment process, bacteria in the WAS were ruptured by mechanical jet and smashed under pressurized conditions. The protein concentrations in the sludge varied significantly after pretreatment. Protein concentration increased according to jet times and pressure. In batch experiments, volatile solids (VS) removal efficiencies were 13 similar to 50% when the WAS pretreated once under 30 bar was fed into an anaerobic digester with 2 similar to 26 day retention time. In the same operating conditions, when intact WAS was fed into the digester, VS removal efficiencies were 2 similar to 35%. Therefore, it is recognized that higher digestion efficiencies of the WAS were obtained through a mechanical pretreatment of sludge. (C) 1997 IAWQ. Published by Elsevier Science Ltd.