Enhancement of sludge dewaterability by electrolysis coupled with peroxymonosulfate oxidation process: Performance, mechanisms and implications

Abstract

With the rapid increase in waste activated sludge (WAS), it is urgent to develop appropriate dewatering processes to diminish sludge volume and improve disposal efficiency. In this study, an advanced oxidation process using electrolysis coupled with peroxymonosulfate (E/PMS) was applied to improve the dewaterability of WAS. The results indicated that the sludge water content (WC) and capillary suction time (CST) dropped from 98.4 ± 0.2% and 220.1 ± 2.3 s to 70.7 ± 0.8% and 63.0 ± 1.2 s, respectively, under the following conditions: an electrolysis voltage of 20 V, an electrolysis time of 20 min, and 200 mg/g TS PMS. The increase in sludge zeta potential, surface hydrophobicity, and flowability indicated a significant improvement in sludge dewaterability. SO4•−, O•H, and O21 generated in the E/PMS process were responsible for the improvement of WAS dewaterability. These reactive oxygen species damaged extracellular polymeric substances (EPS), decreased fluorescent EPS components, and transformed the extracellular protein secondary structures by influencing the H-bond actions that maintain the α-helix. The bound water content, and apparent viscosity of WAS were found to be reduced, which was also attributed to an increase in dewatering capacity. Additionally, E/PMS treatment enhanced the degradation of organic matter in sludge and reduced the toxicity of the filtrate as well as the bioavailability of heavy metals. The cost analysis found that the E/PMS process was relatively economical and has great potential for practical application.