Degradation of emergent contaminants by UV, UV/H2O2 and neutral photo-fenton at pilot scale in a domestic wastewater treatment plant

This study focuses on the removal of 22 selected micropollutants in an effluent from a municipal wastewater treatment plant (MWTP) at pilot scale. A reactor of 37 L with five low pressure mercury lamps emitting at 254 nm (UV254) was used. The 22 micropollutants include 15 pharmaceuticals, 2 X-Ray contrast medias, 1 corrosion inhibitor and 4 biocides/pesticides. Five of these 22 compounds were used as indicative substances as proposed by the Swiss Federal Office for the Environment (FOEN) (carbamazepine, diclofenac, sulfamethoxazole, benzotriazole and mecoprop). Treatments included UV254 light alone, UV254+H2O2 and UV254+H2O2+Fe3+. Wastewater coming from the MWTP already contained iron with an average total iron of 1.6 mg L-1. Original pH was not modified and remained between 6 and 7. The parameters changed during the experiments to find the optimal conditions were: wastewater flow rate (2-14 m3 h-1), H2O2 concentration (20-50 mg L-1) and Fe (III) concentration (0-4 mg L-1). Chemicals removal rates were greater than 80% for the majority of the flow rates tested. Operating costs for the different conditions evaluated were also estimated and compared.