Optimization and control strategies of aeration in WWTPs: A review

Over the recent decades, the escalating expenses associated with energy provision alongside the implementation of rigorous ecological regulations have engendered a noteworthy concern pertaining to energy consumption within the water sector. The reduction of energy consumption and the improvement of effluent quality to meet more stringent discharge limits pose significant challenges for wastewater treatment plants (WWTPs). Most of the energy consumption in WWTPs is attributed to aeration, especially in secondary treatment processes where microorganisms rely on a significant supply of oxygen to sustain their life activities and degrade pollutants. This paper reviews the common secondary treatment processes (oxygen ditch, biological aerated filter, sequential batch reactor, membrane bioreactor) and their energy consumption, and examines the energy consumption and efficiency of aeration in WWTPs in different countries and regions. To address the high energy consumption of aeration, methods for energy saving and consumption reduction are discussed from three aspects: aerator design, mass transfer enhancement, and aeration control strategies. The aerator assumes a pivotal function in determining the characteristics of gas-liquid distribution characteristics in the reactor, which then affects the mass transfer. Mass transfer enhancement in the reactor can improve the oxygen transport efficiency between gas, liquid, and activated sludge. Based on the actual operation conditions, aeration control strategies can adjust the aeration rate to provide accurate air supply and achieving dissolved oxygen (DO) control, thereby reducing the high energy consumption caused by excess aeration. Finally, this study proposes research directions for optimizing the aeration process in WWTPs, including investigating the mechanism of DO transfer to microorganisms, exploring novel oxygen supply modes, and improving energy management of plant-wide consumption to enhance the plant's energy self-sufficiency. Future WWTPs should be low-energy, high-efficiency, intelligent, and environmentally friendly to address the energy shortages and accommodate the large-scale development and unmanned operation of WWTPs.