Pilot studies using hollow fiber nanofiltration membranes to determine the PFAS removal depending on water composition and operation conditions.
To comply with the new German drinking water regulations (Drinking Water Ordinance 2023) concerning the limits set for PFAS groups, total PFAS-20, and PFAS-4 in affected water supplies, membrane filtration through hollow fiber nanofiltration (NF) presents a potential future method for PFAS removal. Advantages of this technology over existing methods include the absence of post-treatment of the permeate, as it still contains minerals from the untreated water and can be directly utilized as drinking water. Conversely, removing PFAS via reverse osmosis membranes (RO) requires post-treatment, such as mineralization, to distribute the water as drinking water.
In addition to PFAS removal, hollow fiber nanofiltration membranes can also fulfill other tasks, including the removal of particulate water constituents (microorganisms, turbidity), and higher molecular weight substances. Due to the low retention of the membranes for monovalent ions and cross-flow operation, concentration polarization at the membrane surface is reduced, potentially allowing to avoid the addition of antiscalants and mitigating concentrate disposal issues.
Within the framework of the KapillO-PFAS project, PFAS elimination with hollow fiber nanofiltration is initially examined using a laboratory test bench and then tested in semi-technical facilities. To verify the retention determined in the laboratory tests, a semi-technical pilot plant with the hollow fiber membrane type is operated at five different sites for three months each, to determine changes in retention depending on water composition and operation conditions during long-term operation.
Statements regarding PFAS and selected ion retention, possible operational modes and yields, resulting filtrate and concentrate characteristics, and the necessity of antiscalant use are obtained both in laboratory and long-term operation phases.
