Integration of ultraviolet irradiation with electrochemical chlorine and hydrogen peroxide production for micropollutant abatement

This research evaluated integrating ultraviolet (UV) irradiation with electrochemical chlorine (Cl2) and/or hydrogen peroxide (H2O2) production for micropollutant abatement in water treatment. Combining UV with anodic Cl2 production (E-UV/Cl2) effectively abated gemfibrozil and naproxen, but ineffectively abated ibuprofen due to its low reactivity with chlorine radicals (e.g., ClO• and Cl2-•). In comparison, combining UV with cathodic H2O2 production (E-UV/H2O2) more effectively abated ibuprofen, but less efficiently abated gemfibrozil and naproxen due to the significant scavenging of •OH by the water matrix. Moreover, simultaneously producing Cl2 and H2O2 during UV irradiation (E-UV/Cl2/H2O2) in an undivided reactor did not further enhance micropollutant abatement compared to the E-UV/H2O2 process because of the mutual consumption of anodically generated Cl2 and cathodic generated H2O2. In contrast, by separating the anodic and cathodic compartments with an anion exchange membrane and operating the E-UV/Cl2/H2O2 process in an anode-to-cathode configuration, all test micropollutants could be adequately abated through the sequential oxidation with the selective chlorine radicals and non-selective •OH in the anodic and cathodic compartments. In general, the concentrations of micropollutants could be abated by 84–100% with a short hydraulic residence time (HRT) of 9.4 min and feasible energy demand (EEO ≤ 3.15 kWh/m3-log) in the selected groundwater and secondary wastewater during the E-UV/Cl2/H2O2 process in the divided reactor. The results indicate that different synergistic effects can be obtained for micropollutant abatement by combining UV and electrochemical processes in varying configurations, and the divided E-UV/Cl2/H2O2 process is a more robust and energy-efficient method for micropollutant abatement during decentralized water treatment.