Trends in Advanced Wastewater Treatment Technologies: From Membrane Bioreactors to Advanced Oxidation Processes

Growing water scarcity, climate change, and increasingly stringent environmental regulations have intensified the need for advanced wastewater treatment technologies capable of removing emerging contaminants and enabling safe water reuse. This review provides an integrated assessment of recent trends in membrane bioreactors (MBRs) and advanced oxidation processes (AOPs), including their role in hybrid treatment systems, with emphasis on contaminant removal efficiency, energy demand, operational complexity, and transformation product formation. In parallel, an exploratory statistical analysis of EUROSTAT indicators—population connected to wastewater treatment plants, Water Exploitation Index (WEI), freshwater availability, and sludge production—was conducted to examine relationships between treatment infrastructure and pressures on water resources across Europe. Correlation and principal component analyses reveal weak to moderate and predominantly indirect relationships between infrastructure expansion and water stress, highlighting that connectivity alone does not reduce resource pressure in the absence of water reuse and advanced treatment. The combined technological and statistical evidence demonstrates that reuse-oriented MBR–AOP systems are critical for improving effluent quality, mitigating emerging pollutant risks, and supporting circular, climate-resilient water management strategies under European policy frameworks.