Matrix-dependent UVC/H2O2 degradation of pharmaceuticals in reverse osmosis concentrate

Abstract Reverse osmosis is widely applied as an advanced treatment technology due to its high efficiency in removing organic micropollutants from wastewater. However, this process inevitably produces a residue with a high contaminant load, posing environmental challenges and requiring effective post-treatment strategies. In this study, the photoperoxidation process was investigated for the degradation of six pharmaceuticals (acetaminophen, caffeine, naproxen, progesterone, sulfathiazole, and testosterone) in reverse osmosis concentrate and other complex aqueous matrices to assess matrix-driven effects on process efficiency. Experiments in ultrapure water showed negligible removal by UVA photolysis and H 2 O 2 alone, whereas UVC irradiation promoted compound-dependent degradation. UVC-photoperoxidation significantly enhanced removal efficiency, and under optimized conditions (UVC/H 2 O 2 0.87 mmol L −1 ), all pharmaceuticals were degraded within 40 min. Matrix composition strongly governed degradation efficiency. In reverse osmosis concentrate, all compounds were efficiently degraded within 30 min. Similar rapid degradation was observed in the post-Membrane Bioreactor effluent. In contrast, matrices with high dissolved organic matter content, such as surface water and solutions containing elevated humic acid concentrations, strongly inhibited degradation due to UV light attenuation and radical scavenging. Low humic acid accelerated degradation, underscoring dissolved organic matter’s dual role. Naproxen was the least persistent compound, whereas acetaminophen was the most persistent. In saline matrix such as reverse osmosis concentrate, efficient degradation was observed despite elevated conductivity, suggesting the contribution of additional oxidative pathways. Overall, the results show that the matrix composition plays a decisive role in degradation efficiency, emphasizing the need to consider the characteristics of the water when evaluating advanced oxidation processes.