Enhancement of Sludge Dewaterability by Ozone Treatment

Abstract

The effects of ozone treatment on the dewaterability of activated sludge wasted from a sewage treatment plant were investigated in this study. Following ozone treatment, sludge was dewatered using a pressure filter. The sludge filterability evaluated by SRF deteriorated with ozone dosage at relatively low ozone doses. However, at ozone doses higher than 0.6gO3/gSS, the SRF of the ozone treated sludge became comparable with the value for the sludge without ozone treatment. It is suggested that the oxidation of the viscous, high molecule organics attached at cell surface reduces the surface charge of sludge particle and promotes flocculation at relatively high ozone doses. Ozone treatment also cause the release of bound water trapped inside cells or floes, resulting in significant reduction of cake water content after dewatering. In terms of cake volume, more than 55 % reduction was obtained at 0.4gO3/gSS. These observations suggest that ozone treatment has potential to significantly enhance sludge dewaterability and to produce a more compact cake without severe deterioration of its filterability.