Advanced Oxidation Process in the Sustainable Treatment of Refractory Wastewater: A Systematic Literature Review

More than 4 billion people yearly suffer from global water scarcity amid climate change, rapid population growth, and growing industrial activity. Due to the high concentrations of recalcitrant organic compounds, refractory wastewater is highly resistant to conventional biological treatment and represents a critical obstacle for water reuse and sustainable water management. A systematic literature review of 35 peer-reviewed articles published from 2010 to 2025 is provided to evaluate the utilization and sustainability potential of advanced oxidation processes (AOPs) for treating recalcitrant wastewater. Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework, the review assesses numerous AOPs, such as ozonation, UV/H2O2, Fenton reactions, and photocatalysis, while also evaluating their performance, efficiency, and integration ability. The results show that AOPs demonstrate pollutant removal rates often greater than 96%, reduce sludge formation, and improve effluent biodegradability. They can be applied at different treatment stages, combined with any renewable energy systems, and therefore can scale and be sustained, thereby aligning with UN Sustainable Development Goal 6. AOPs provide a technically feasible and eco-friendly solution for higher quality wastewater treatment. In the face of increasing pressure on global water resources, and the urgent need for sustainable water resource management, this study offers valuable insights for policymakers and practitioners aiming to adopt resilient and circular strategies for water.