Integration of advanced oxidation processes (AOPs) and membrane bioreactors (MBRs) for wastewater treatment: A review

The increasing complexity of industrial and municipal wastewaters containing pharmaceuticals, dyes, endocrine disruptors, and recalcitrant organic pollutants, necessitates advanced treatment strategies beyond conventional biological and physical methods. Membrane bioreactors (MBRs) have emerged as an efficient technology for high-quality effluent production through combined biological degradation and membrane filtration. However, their performance is limited by membrane fouling and the persistence of non-biodegradable contaminants. Advanced oxidation processes (AOPs), capable of generating highly reactive radicals, offer a complementary pathway for degrading resistant organics and enhancing effluent quality. This review critically examines the integration of AOPs with MBRs in various configurations, including AOPs applied before, during, or after biological treatment. Specific hybrid systems such as ultraviolet/hydrogen peroxide (UV/H₂O₂), ozonation, persulfate-based oxidation, Fenton reactions, photocatalysis, electrochemical methods, ultrasonic processes, plasma, and electron beam treatments are explored in detail. The synergistic benefits of hybridization include improved pollutant degradation, reduced fouling, enhanced disinfection, and greater potential for water reuse. Challenges such as energy demand, operational costs, catalyst stability, and scalability are also discussed. Overall, AOP–MBR integration presents a promising, future-oriented solution for sustainable wastewater treatment, aligning with global goals of water reuse, resource recovery, and environmental protection.