Effects of Loosely Bound EPS Release and Floc Reconstruction on Sludge Dewaterability

Abstract

Loosely bound extracellular polymeric substances (LB-EPS) are highly hydrated biopolymers and play important roles in sludge biofloccualtion and dewaterability. Disruption or solubilization of LB-EPS will promote the alternation of sludge structure and the release of trapped water. In the present study, ultrasonication was employed to extract LB-EPS into the supernatant and release trapped water within them. Excellent performance in enhancing ultrasonicated sludge dewatering was observed under the combined Fe3+(20 mg/g dry sludge (DS)) and Ca2+ (30 mg/g DS) addition. The above fact highlighted the probability to enhance the sludge dewaterability by the dosage of small amount of cations. Further, the combined effects of ultrasonication and multivalent cation addition on floc regrowth on sludge dewaterability were investigated and the possible mechanisms involved in the reorganization of sludge structure and the biofloccualtion process were also explored. In conclusion, the combination of ultrasonication and multivalent cation addition was promising to improve sludge dewaterability.