Improving the Dewaterability of Sewage Sludge Using Rice Husk and Fe2+-Sodium Persulfate Oxidation

Abstract

Physical conditioners or skeleton builders are usually used to improve the dewaterability of sewage sludge. In this study, low-cost rice husk (RH) was evaluated as an alternative skeleton builder and combined with Fe2+ and sodium persulfate (SPS) for sewage sludge conditioning. The results show that the sewage sludge conditioned with RH and Fe2+/SPS showed good dewaterability, and the capillary suction time was reduced by 92.8% under optimal conditions. With use of response surface methodology, the optimal composite conditioner concentrations were 151.5 mg/g dry solid (DS) of SPS, 46 mg/g DS of Fe2+, and 333 mg/g DS of RH. After the sludge was conditioned with Fe2+/SPS, some extracellular polymeric substances (EPS) were destroyed, which resulted in the dissolved protein and polysaccharide amounts in the filtrate increasing. The water content analysis indicated the bound water was converted to free water because of the EPS degradation. The particle size analysis showed that the sludge flocs became smaller....