Improvement of sludge dewatering by calcium peroxide activated with pyrite: performances, mechanisms and implications

Abstract

This study proposed a novel sludge conditioning technology using calcium peroxide (CaO₂) activated with pyrite for improving the dewaterability of waste activated sludge (WAS). The results showed that the water content of the sludge cake decreased from 93.33% to 90.80%, and the SCST decreased to 0.52 at the optimal conditioning (pyrite dose of 32.61 mg g_TS⁻¹, CaO₂ dose of 30 mg g_TS⁻¹). Furthermore, a comprehensive investigation indicated that the underlying mechanism of dewaterability improvement can be attributed to the transformations of extracellular polymeric substances (EPS). The results of the FTIR protein secondary structure and interfacial free energy showed that combined conditioning enhanced the hydrophobicity of the sludge. In addition, the repulsive force of sludge particles and the bound water content in sludge flocs both decreased after conditioning based on the results of zeta potential and potential barriers. Overall, these findings provided theoretical insights into the role of EPS in dewaterability improvement and an alternative sludge conditioning scheme.