Advanced oxidation technologies combined with direct contact membrane distillation for treatment of secondary municipal wastewater

Abstract In this work, the combination of advanced oxidation technologies (AOTs) and direct contact membrane distillation (DCMD) was investigated for the treatment of municipal wastewater collected from a secondary clarifier of a conventional municipal wastewater treatment plant (MWWTP). Average efficiencies higher than 95 % were obtained with ozonation (O3) and photolytic ozonation (UV/O3) for the removal of 12 micropollutants present in the wastewater samples, whereas only near 50 % was achieved with UV-peroxidation (UV/H2O2). When the ozone-based processes were combined with DCMD, the concentration of these micropollutants were below the detection limits in the respective permeate, increasing the quality of the treated water. However, the permeate fluxes in DCMD were remarkably higher when the wastewater was pre-treated with UV/H2O2 instead of O3, most probably due to the better disinfection achieved with UV/H2O2. It was also confirmed that the dissolved organic carbon (DOC) of the wastewater strongly affects the permeate fluxes achieved by DCMD, the combination of the oxidation and membrane separation processes being more appropriate for wastewaters with low DOC contents (