New insight on the combined effects of hydrothermal treatment and FeSO4/Ca(ClO)2 oxidation for sludge dewaterability improvement: From experimental to theoretical investigation

A combination of hydrothermal treatment and FeSO4/Ca(ClO)(2) oxidation was developed to enhance the dewatering performance of sludge. First, capillary suction time (CST), specific resistance to filterability (SRF), and water content (Wc) are used to evaluate the sludge dewaterability. The effect of the hydrothermal temperature, the concentration and the molar ratio of FeSO4 and Ca(ClO)(2) on the sludge dewatering performance was examined to determine the optimal conditions. Furthermore, the mechanism of the degradation of EPS in sludge was studied using density functional theory (DFT), e.g., electrostatic potential (ESP) analysis, bond order analysis, and bond dissociation enthalpy (BDE) analysis. The results show that the sludge dewaterability was significantly improved with the combined method. The floc structure and the oxygen-containing groups of EPS in sludge are the key reasons for its hydrophilicity and high water content. The combined method can enhance sludge dewatering by breaking the floc structure and removing oxygen functional groups, which is a promising technology for sludge dewatering.