Current progress in the analysis and control of organic contaminants in reverse osmosis concentrate from industrial wastewater zero liquid discharge: A comprehensive review

Reverse osmosis concentrate (ROC), generated during zero liquid discharge (ZLD) processes for industrial wastewater treatment, is characterized by high-salinity and complex organic constituents, posing significant challenges to its effective management. In particular, elevated salinity can hinder the degradation of organic contaminants, leading to their persistence, which increases the operational burden of ZLD systems, particularly during evaporation, and compromises the purity of recovered salts. Therefore, precise characterization of organic contaminants and the development of targeted and efficient treatment strategies in the ROC are essential. This review provides a comprehensive overview of recent advances in the ROC, including its sources, characterization methods, and treatment technologies. Advanced spectroscopic and mass spectrometric techniques for analyzing organic contaminants in high-salinity systems are highlighted. Particular emphasis is placed on advanced oxidation processes (AOPs), especially electrochemical oxidation, to elucidate degradation mechanisms under high-salinity conditions, with a focus on salt-induced effects and corresponding mitigation strategies. In addition, current limitations and challenges associated with ROC characterization and treatment are critically analyzed. Furthermore, future perspectives are proposed to guide the development of more efficient and robust technologies for ROC management within ZLD systems. Overall, effective ROC management requires a deeper understanding of salt-induced effects and the development of integrated characterization/treatment strategies for high-salinity systems.