Reduction of excess sludge production in sequencing batch reactor through incorporation of chlorine dioxide oxidation

In this study, chlorine dioxide (ClO2) instead of chlorine (Cl2) was proposed to minimize the formation of chlorine-based by-products and was incorporated into a sequencing batch reactor (SBR) for excess sludge reduction. The results showed that the sludge disintegrability of ClO2 was excellent. The waste activated sludge at an initial concentration of 15 g MLSS/L was rapidly reduced by 36% using ClO2 doses of 10 mg ClO2/g dry sludge which was much lower than that obtained using Cl2 based on similar sludge reduction efficiency. Maximum sludge disintegration was achieved at 10 mg ClO2/g dry sludge for 40 min. ClO2 oxidation can be successfully incorporated into a SBR for excess sludge reduction without significantly harming the bioreactor performance. The incorporation of ClO2 oxidation resulted in a 58% reduction in excess sludge production, and the quality of the effluent was not significantly affected.