Acid-heat pretreatment was used to improve the sludge dewatering performance by breaking the structure of sludge flocs,and a mathematical model simulated about sludge de-watering capability was obtained,besides the relevant factors were optimized based on the Box-Behnken response surface method.The results showed that acid-heat combined pretreatment could greatly improve the sludge dewatering performance,and it was optimized in the case of a pH of 1.0 and temperature of 59.2℃ for 34.1 min,the water content of sludge cake reached as low as 59.0％and SRF was 7.48×1012 m/kg.In terms of mechanism,the acid-heat combined pretreatment improved the de-watering performance of sludge mainly through the conversion of a large amount of tightly bound extracellular polymetric substances(TB-EPS)to soluble extracellular polymetric substances(S-EPS)and loosely bound extracellular polymetric substances(LB-EPS)to change the surface charge of sludge,reducing the amount of protein in TB-EPS,approximately equal to the increasing amount of protein in both S-EPS and LB-EPS.And particle size of sludge greatly enlarged under acid-heat combined pretreatment,but the type and concentra-tion of free amino acids in sludge had relatively lesser impact on its dewatering performance.
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