Influence of ultrasonic cell disintegration on excess sludge reduction in a Moving Bed Biofilm Reactor (MBBR)

Abstract

Sludge handling is a common issue in all biological wastewater treatment methods. In this study, sonication technique as a state-of-the-art technology has been applied to a continuous MBBR system with the aim of sludge reduction. A novel configuration of MBBR with an additional recycle stream of sonicated sludge was used as the experimental setup. Based on exposed energy and sludge disruption performance, optimized sonication density and exposure time were obtained 1.5 W/mL and 15 min, respectively. This condition provided 42.2% increase in soluble COD as a result of sludge disintegration. Our results revealed that the performance of MBBR and excess sludge reduction were affected by sonicated sludge recycle ratio (SRR). The energy consumption index (EC) was defined to evaluate the optimum recycle ratio. The maximum excess sludge reduction was observed at 80% SRR, however, the effluent COD and turbidity were deteriorated considerably in comparison to control reactor. The recommended SRR was 60%, where the COD removal efficiency, effluent turbidity and excess sludge reduction were 89.7%, 19 NTU and 61.7%, respectively. Under this condition, the lowest energy consumption of 72.9 kWhkg removed sludge was observed.