Removal of pharmaceuticals from a WWTP secondary effluent by ultrafiltration/reverse osmosis followed by electrochemical oxidation of the RO concentrate

• Removal of emerging pollutants from WWTP secondary effluent by a tertiary treatment that combines UF and RO
• Electrooxidation as means of mineralization of micropollutants contained in the RO concentrate

This study aims to assess the removal of emerging contaminants from municipal wastewaters using a pilot system that integrated ultrafiltration (UF), reverse osmosis (RO), and electrooxidation, which mineralized the RO concentrate. Initially, the study monitored 77 emerging contaminants in the influent and effluent of a wastewater treatment plant (WWTP). Most of the compounds were detected in significant amounts in the WWTP effluent.A group of 12 compounds that represent the most prevalent therapeutic pharmaceutical categories was selected to monitor their removal by UF/RO. For the majority of the micropollutants, the UF removal efficiency was less than 20%. Excellent removal efficiencies were achieved with the RO treatment. As a result, the concentrations of the emerging contaminants in the RO permeate varied between 44 ng/L for naproxen and 4 ng/L for ofloxacin, and furosemide, bezafibrate and fenofibric acid were not detected. After the RO treatment, electrooxidation of the RO concentrate with boron-doped diamond electrodes reduced the total micropollutant content in the RO concentrate from 149 μg/L to less than 10 μg/L. Increasing the intensity of the electrooxidation treatment is expected to further reduce the micropollutant concentrations.