Dewatering of conditioned sludge in small wastewater treatment plants

Parameters characterizing the dewatering process of sewage sludge in small wastewater treatment plants (WWTPs) have been analyzed. Two municipal wastewater treatment plants of comparable capacity and similar technology of sewage treatment were selected to the analysis. Comparison of dewaterability of unprepared and conditioned sludge was made. During preliminary tests, the capillary suction time (CST) of sludge conditioned with cationic polyelectrolyte was determined. Next, for the optimal doses of selected polyelectrolyte, more detailed technological experiments were conducted such as vacuum filtration and susceptibility to the gravitational thickening. Tested sludge had very low susceptibility to thickening. The final volume of unprepared tested samples after 2 hour thickening was 977.0 cm3, while the initial volume of thickened sludge was 1000 cm3.The lowest value of final hydration for conditioned sludge was 64.0%.