Investigating the effects of different cationic charge flocculation polymers on municipal wastewater sludge dewatering

Abstract

The minimization of sludge produced by municipal wastewater treatment plants (MWWTPs) is critical as its handling accounts for approximately 50% of the total operating cost. The challenges in predicting dewatering performance can be overcome by optimizing the sludge treatment process, especially conditioning and dewatering. This study aimed to investigate sludge dewaterability at four different MWWTPs, using a gravity drainage test unit and a bench-scale press. The effect of differently treated effluent used as a solvent to mix the flocculation polymers was observed during dewatering. The membrane bioreactor (MBR) treated effluent yielded the highest filtrate volume in the lowest amount of time, with the least polymer flocculant dosage. The Box Behnken Design model fitted the data and proved a relationship between polymer dosage, cake solids concentration, and cake height during the bench-scale press tests. Highlights The type of water used for polymer flocculant dissolution has, to an extent, a considerable impact on the gravity drainage of the sludge.; Increasing polymer flocculant dosing is not directly proportional to the cake height and cake dryness.; Significant correlation between sludge characteristics (e.g. feed solids) and the cake formed.;

Keywords

• activated sludge
• cationic polymer
• dewatering
• flocculant
• gravity drainage
• sludge treatment