ABSTRACT
It was found that sludge total solid (TS) concentration was equal to chemical oxygen demand (COD), while volatile solid (VS) was 1.5 times of COD concentration. R2 of linear regression of TS and VS with COD was 0.9314 and 0.9228 respectively. Total COD in sludge was approximately 60% of that removed in water treatment process. Sludge contained high level protein and low fat. The TS of present gravity thickening sludge was universally lower than 3.3%. Efficiency of vacuum filtration process was determined by sludge type, sludge solid concentration, PAM molecular weight and PAM addition dose. Under - 34.7 kPa pressure, sludge dry solid filtration thickening rate of primary sludge was up to 31 kg/(m2 x h). While, for wasted actived sludge the rate was lower than 15 kg/(m2 x h). Rate of gravity thickening sludge was up to 43 kg/(m2 x h). TS of vacuum filtrate were lower than 1.5 g/L.