Tapping the energy potential from wastewater by integrating high-rate activated sludge process with anaerobic membrane bioreactor

Advances in wastewater treatment have pushed forward new developments for energy recovery from wastewater. Integrating high-rate activated sludge process (HRAS) with anaerobic membrane bioreactor (AnMBR) is promising towards energy-positive rather than energy-consuming wastewater management. In this study, the overall performance of the lab-scale HRAS-AnMBR system was investigated under different operating conditions through experimental and modeling investigations. The decrease in sludge retention time (SRT) from 2 to 0.5 days of the HRAS process could improve chemical oxygen demand (COD) capture efficiency by up to 43%, realizing an overall COD recovery of 30% with methane production of 0.25 L/g COD. Simulation results further confirmed that the overall performance highly depended on dissolved oxygen, solid retention time, and influent composition. More importantly, there could be a trade-off between carbon capture and effluent quality in the HRAS process with different operating conditions. The findings of this study indicate that the integrated process has potential for energy recovery while multiple operating parameters in the HRAS process should be overall considered to maximize the energy recovery potential and improve the effluent quality of the integrated HRAS and AnMBR system.