Per- and polyfluoroalkyl substances in foam and dewatering streams at wastewater treatment plants

The occurrence of per- and polyfluoroalkyl substances (PFAS) in wastewater treatment plants (WWTPs) is well recognized. While several studies have examined the occurrence of PFAS in WWTPs, studies assessing the extent to which unit processes impact PFAS phase distribution are relatively lacking. Herein, PFAS enrichment in foams generated during aeration and PFAS accumulation in solids dewatering streams were evaluated in WWTPs. Results of this screening-level study showed that perfluorooctane sulfonate (PFOS) concentrations were enriched up to three orders of magnitude in foams relative to the aqueous phase. Similarly, total PFAS concentrations in solids dewatering streams were enriched up to 380 times relative to the aqueous influent. The PFAS mass in the dewatering stream was a significant component of the overall PFAS mass exiting the WWTP at one of the facilities examined. Results of this study suggest that there is potential to mitigate PFAS by improved management of these foams and dewatering waste streams.