Keywords: membrane bioreactors, MBR, dissolved oxygen, aerobic process, energy consumption, oxygen uptake rate, nitrification, denitrification, energy saving, energy efficiency, chemical oxygen demand, COD, total nitrogen removal, sludge flocculation, membrane filtering
Low dissolved oxygen membrane bioreactor processes (LDO–MBRs): a review
Aeration energy demands for bioprocesses and membrane scouring in membrane bioreactors (MBRs) account for 50% to over 70% of the total operational energy consumption. Energy saving achieved by operating MBRs under low dissolved oxygen (DO) would be an interesting approach to bring MBRs to higher levels of efficiency. This review paper is first carried out to provide a systematic investigation on how to achieve good treatment performance and save energy in terms of lowering DO for MBRs. As a result, small scale MBRs operated under low DO (0.5–0.8 mg/L) can allow the process to work properly. At very low DO (0.2 mg/L), MBRs can still have a good performance, e.g., chemical oxygen demands and total nitrogen (TN) removal efficiencies are higher than 90% and 60%, respectively. However, low DO could lead to poor sludge flocculation resulting in increasing small particles which deteriorate the membrane filterability.