AN INNOVATIVE APPROACH TO REDUCE EXCESS SLUDGE PRODUCTION IN THE ACTIVATED-SLUDGE PROCESS

A new process has been developed to reduce excess sludge production, i n which both excess sludge digestion and wastewater treatment are cond ucted simultaneously in the same aeration tank. The ozonation enhances biological degradation of the activated sludge, which is decomposed i n a subsequent biological treatment. A considerable amount of biomass is mineralized biologically in proportion to the amount of recirculate d biomass from the ozonation stage to the biological stage. It was obs erved that the amount of excess sludge is reduced to nearly zero when 1.2 kg/m(3)-aeration tank volume Of biomass is recirculated in a day f rom the biological stage to the ozonation stage at a BOD loading of 1. 0 kg/m(3)/d. A biomass concentration of 4200 mg/L was maintained at 1. 0 kg-BOD/m(3)/d without drawing excess sludge for 6 weeks of experimen tal period under ozone dose of 0.05 g-O-3/g-SS and recirculation rate at 0.3 d(-1). Only a limited difference in the effluent quality was ob served between the new process and the conventional activated sludge p rocess.