New Insight on the Combined Effects of Hydrothermal Treatment and FeSO4/Ca(ClO)2 Oxidation for Sludge Dewaterability Improvement: Moisture Distribution and Noncovalent Interaction Calculation

A combination of hydrothermal treatment and FeSO4/Ca(ClO)2 oxidation was developed in our previous work and was proved to be significantly useful for improving the sludge dewaterability. The dewatering mechanism of the sludge after the combined treatment of hydrothermal treatment and FeSO4·7H2O/Ca(ClO)2 was obtained for the first time based on the moisture distribution analysis. Moreover, the noncovalent interaction between the hydrophilic sites of sludge EPS in sludge and water molecules was studied for the first time by using density functional theory. The electrostatic potentials of three representative EPS molecules, that is, dextran, poly-gamma-glutamate, and poly-l-lysine, were calculated and analyzed. AIM and RDG of the representative EPS·water complex models were calculated to study the noncovalent interaction mechanism. The moisture distribution and noncovalent interactions analyzed in this paper will provide information for improving sludge dewatering performance.