Improving the Dewaterability of a Filter Press through Optimization of the Coagulation Conditions of Sewage Sludge

Abstract

This study applied a filter press for dewatering that uses pressure to reduce the water content of sludge generated in sewage treatment plants and evaluated the improvement of dewaterability under various coagulation conditions according to the type of coagulants, amounts, and pH conditions. The improvement of dewaterability was evaluated by measurement of time to filter (TTF), change in zeta potential, and sludge cake generated after filter press dewatering. It was found that under the applied coagulation conditions, inorganic coagulants were suitable for filter press dewatering. The optimum conditions were PAC with a dose of 70 mg/gTS, pH 10 for mixed sludge, and PAC with a dose of 100 mg/gTS, pH 6 for anaerobically digested sludge. Under optimal coagulation conditions, the water content of the sludge cake was 57% and 65%, respectively, marking a reduction by 19-27% compared to conventional centrifuge dewatering.