Identifying Challenges and Potential Strategies for Mitigating PFAS Based on Observed PFAS Fate and Transport in Wastewater Treatment Plants

Efforts as part of multiple on-going and recently completed Water Research Foundation projects have closely evaluated poly- and perfluoroalkyl substance (PFAS) fate and transport throughout unit processes in wastewater treatment plants (WWTPs) and in finished biosolids. Collectively, these efforts have shown that the majority of PFAS in WWTP influent, effluent, and finished biosolids are precursors that can consist of semi-quantifiable analytes. In biosolids, these semiquantifiable PFAS are dominated by phosphonic acid-based PFAS, including polyfluoroalkyl phosphoric acid diesters (diPAPs). The transformation of these diPAPs to fluorotelomer carboxylic acids and perfluoroalkyl acids often plays an important role in controlling PFAS levels in WWTP effluent and in overall PFAS leaching from biosolids. Aeration and solids dewatering processes in WWTPs also serve as a means for concentrating PFAS in foams/aerosols and dewatering concentrate, respectively, and may serve as an opportunity to mitigate PFAS in WWTP effluents.