Impact of advanced oxidation process (AOPs) pretreatment on enhancing sludge dewaterability: new insights through EPS protein and sludge hydrophilicity/hydrophobicity properties

Abstract

Abstract Advanced oxidation processes (AOPs) are important for improving sludge dewatering efficiency. In this study, AOPs such as pretreatment with sodium persulphate and calcium peroxide were investigated as methods for improving the dewaterability of waste activated sludge (raw sludge), digested sludge (DS), and sludge digested for 3 days (DS-3). The results showed that persulphate and peroxide could effectively improve the dewaterability of sludge. The results suggested that the maximum increment of free moisture of 4.69% was achieved for the DS-3 of pretreatment with persulphate, and the mechanism investigation revealed that AOPs pretreatment could enhance sludge floc disintegration, degrade the protein (PN) fraction of extracellular polymeric substances (EPS), and accelerate the release of mechanically bound moisture. Free moisture was significantly negatively correlated with the DS PN concentration in extra-microcolony polymers (R = 0.850, p < 0.01). Compared with RS, the organic matter content of DS and DS-3 sludge samples pretreated by AOPs was lower, viscosity was decreased, zeta potential was closer to zero, and the strength of amino, amide II and other hydrophilic functional groups decreased or disappeared. Under the same AOPs conditions, the dewateratbility of digested sludge is better than that of RS. This study reveals the mechanisms of sludge AOP conditioning and provides a theoretical basis for practical applications.