An absolute barrier to PFAS in RO concentrate – no PFAS discharge to the environment in the drinking water sector (PAH PFAS)

An inventory study (KWR 2021.040) has shown that drinking water utilities find PFAS in their sources. PFAS are removed effectively during treatment with reverse osmosis (RO) but this results in a concentrate stream in which PFAS are found in concentrated form. Discharging this concentrate stream with PFAS into the environment is undesirable and this proposal presents a new concept to remove PFAS before discharge from the RO concentrate stream. With existing (and innovative) techniques, we may be able to provide a solution in the short term to minimise PFAS discharges via concentrate streams into the aquatic environment.


Adding a suitable adsorbent to the RO concentrate stream bonds PFAS to a solid. These adsorbents may work better without competition from other organic matter and/or at higher concentrations of PFAS. This can be achieved with ultrafiltration (UF) and (capillary) nanofiltration (NF) membranes, respectively. In addition to this combination of membrane technologies, foam fractionation could also be used to improve adsorbent performance. Incineration (given the current state of the art) may be a way to treat the waste stream, i.e. the loaded adsorbent and/or foam. A more innovative approach involves research looking at the desorption/regeneration of loaded adsorbents (for example with innovative extraction) and the complete degradation of PFAS (for example with supercritical gasification).


The water matrix of RO concentrate can interfere with good adsorption and finding a suitable adsorbent is a bottleneck (adsorbent selection). Depending on organic material and calcifying components in the concentrate, fouling of the UF/NF membrane is possible (membrane selection). Finally, the disposal or regeneration of the adsorbent loaded with PFAS presents an innovative challenge. The option of foam fractionation with RO concentrate is unknown and innovative.


With existing (and innovative) techniques, we may soon be able to provide a solution that will minimise discharges of PFAS via concentrate streams into the aquatic environment. At the same time, we will establish new scientific insights with respect to PFAS adsorption, filtration, desorption and processing of waste streams containing PFAS.