The occurrence and persistence of PFAS at riverbank filtration sites in the upper Danube basin

Abstract

PFAS are a class of synthetic chemicals used for many industrial and domestic purposes. However, once released in the environment, they are persistent, mobile and toxic. One of the most important transport routes to drinking water is through riverbank filtration. Although this is usually an effective strategy for removing many organic compounds, its effectiveness in removing PFAS is still unknown. The aim of this study is to investigate the occurrence, as well as the spatial distribution of PFAS at riverbank filtration sites and compare these to two pharmaceuticals and various chemical parameters. A one-year sampling campaign was carried out at four transects with different characteristics along the Danube river. Samples were analysed using Liquid Chromatography Mass Spectrometry. Results show that most of the detected PFAS compounds had concentrations lower than 10 ng/l. NaADONA had the highest concentration at all the sites, indicating the presence of an emission source upstream of the monitored sites. For most compounds, there was no concentration reduction between the river and groundwater, implying that no removal processes take place. This was further confirmed with statistical tests, which showed no significant differences between river- and groundwater concentrations. Two sites in Budapest showed higher concentrations of PFOA, PFOS, and GenX in the background water compared to the river, indicating an inland source of these compounds. The current situation imposes no problems for drinking water as the measured concentrations are lower than the legal limit set by the EU Drinking Water Directive. However, any future legal or industrial changes could create problems since results suggest that these compounds are not removed during riverbank filtration.