From batch system toward continuous UV/PS based AOP reactor: the case of tramadol effluent degradation†

The stability of pharmaceutical active ingredients (APIs) and their resistance to conventional treatment methods necessitates the development of degradation methods as point-source treatment before mixing with municipal wastewater. Advanced oxidation processes utilize oxidants such as H₂O₂ or persulfate (PS) to treat organic contaminants and have shown promising results for eliminating APIs from wastewater. This research investigated the degradation of tramadol (TRA), a fully synthetic opioid, in a UVC/PS system, which was selected after evaluating thermal and simulated solar activation techniques. Different concentrations of PS were tested, and the UVC/PS system with [PS]₀ = 0.4 mM achieved complete degradation of 10 mg L⁻¹ [TRA]₀ in 6 min with k_obs of 0.90 min⁻¹ and was chosen for this study. The system was evaluated under different conditions and showed a decrease in reaction rate under acidic conditions and in the presence of bicarbonates or competing natural organic matter. Additionally, high levels of chlorides and nitrates inhibited the degradation. Building on insights from batch treatment experiments, a pilot-scale treatment plant was developed utilizing elements from commercially available UV water-disinfection kits for continuous-flow treatment of pharmaceutical industry effluent. After optimization, the system achieved full degradation of 360 L per day of 10 mg L⁻¹ [TRA]₀ at a cost of $0.296 per m³.