The effects of sodium persulfate pretreatment and calcium peroxide pretreatment on digested sludge and raw sludge dewaterablity

Comparison between the dewatering performance of raw sludge and digested sludge is lacking. In this study, pretreatment with sodium persulphate (SP), calcium peroxide (CP) for improving the dewaterability of raw sludge (RS), digested sludge (DS), and sludge digested for 3 days (DS-3) were investigated. Using ferrous sulfate as a catalyst to produce sulfate radicals from SP. Results suggested that the maximum increment of free moisture of 4.69 % was achieved for the DS-3 of pretreatment with SP, and the mechanism investigation revealed that two kinds of pretreatments could enhance sludge floc disintegration, degrade the protein (PN) fraction of extracellular polymeric substances (EPS), and accelerate the release of mechanically bound moisture. Compared with RS, the organic matter content of DS and DS-3 sludge samples pretreated by SP and CP 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.