Use of Colloidal Gas Aphrons to Remove Per- and Polyfluoroalkyl Substances from Reverse Osmosis Concentrate

Per- and polyfluoroalkyl substances (PFAS) are persistent emerging contaminants that are not destroyed by conventional water and wastewater treatment processes and are a concern to human health and the environment. Reverse osmosis (RO) treatment, which is being adopted to specifically remove emerging contaminants, has proven effective for removing PFAS from water and concentrating the removed PFAS in the RO reject (also known as RO concentrate or “ROC”). Subsequent treatment of ROC to remove PFAS prior to disposal is challenging due to the highly saline nature of these fluids. This study evaluates the use of colloidal gas aphrons as a novel treatment strategy for PFAS removal from ROC with an elevated total dissolved solid (TDS) content (8,200 mg/L). Aphrons were generated using lauric arginate ethyl ester (LAE), a food-grade cationic surfactant, under various operating conditions. The results demonstrate that cationic aphrons can successfully remove up to 97% of long-chain (6 or more carbon atoms) and 75% of short-chain (4–5 carbon atoms) PFAS mass from ROC; optimal removal was achieved using a single-stage 10% aphron dosage.