Emerging Technologies for Water and Wastewater Treatment: Advances, Challenges, and Future Perspectives

Emerging approaches to water and wastewater treatment can complement established processes, but high removal in laboratory tests rarely indicates how well a technology will perform in practice. This targeted critical review examines advanced oxidation, membranes, electrochemical and bioelectrochemical systems, functional adsorbents, biological innovations, hybrid trains and digital tools. Rather than comparing removal percentages in isolation, it considers contaminant fate, matrix effects, operating demands, residual management, environmental burdens and the maturity of supporting evidence. Each technology has conditional strengths: oxidation can transform persistent organics but may create toxic intermediates; membrane separation and adsorption generate concentrates or spent materials; biological and resource-recovery processes depend on stable operation and suitable feed characteristics. The proposed application-specific framework links the treatment objective and wastewater matrix to process limitations, evidence scale and system-level trade-offs. Across the literature, the most persistent gaps concern sustained real-wastewater trials, material durability, secondary residues and comparable energy, cost and life-cycle reporting. Decisions therefore require evidence from complete treatment trains, not laboratory performance alone.