Evaluation of Nanofiltration and Reverse Osmosis Membranes’ Performance for PFAS and Ion Rejection from Drinking Water Sources in Sweden

Per- and polyfluoroalkyl substances (PFAS) include a large group of chemicals that has been used for many decades because of their mechanical and chemical stability. They owe these unique features due to the strong C-F bonds in their molecules. PFAS can be fully or partly fluorinated and the more fluorinated they get, the more persistent they become. They have been used in several industries such as cosmetics, fire extinguishing foams, textile and colour industry. The problem with these compounds is that they persist in the environment and they can accumulate in the food chain, ending up in the human body. Recent research on toxic effects of PFAS showed that they can cause several known diseases and there have been correlations between the PFAS concentrations in the water with different types of cancers, hormone imbalances and many other diseases. Therefore, it is important to remove the PFAS from the water resources as the water resources could be the main PFAS exposure pathway among populations. Presently, many methods are under investigation to treat PFAS and remove it from the drinking water resources. This study focuses on the removal of PFAS through membrane filtration. Nanofiltration and reverse osmosis membranes have a long history in removing organic pollutants and have been also used to treat waters polluted with PFAS. The membrane’s performance under different testing conditions can differ and finding a way to optimize their performance and determining which membranes are most suited for PFAS treatment is a key factor for creating an efficient plant with high PFAS rejection rate. Therefore, for this study, the data for membrane permeability, fouling rate, desalting rate, relative performance, ion rejection rate has been studied. Also, as an addition to the project, closed-circuit operations were conducted to test the mem-branes’ performance in treating highly concentrated feed water. The results of this experiment showed a high desalting potential both for RO and NF membranes and discussed the varia-tions in the permeability of different membranes. Also, high ion rejection rates were observed both for open and closed system configuration. Overall, this study provides valuable insights into the selection and operation of NF and RO membranes for PFAS treatment, highlighting their potential for high ion rejection efficiency and informing the design of more effective and sustainable water purification systems. In addition, another part of this report focuses on the membranes’ ability to concentrate the solutes for resource recovery purposes. This could provide promising insights for the use of NF and RO membranes in integrated systems to extract and recover materials from the wastewater streams.