Identification and Fate of Aqueous Film Forming Foam Derived Per- and Polyfluoroalkyl Substances in a Wastewater Treatment Plant

The fate of per- and polyfluoroalkyl substances (PFASs) derived from aqueous film forming foam (AFFF) was investigated within a wastewater treatment plant (WWTP) receiving large AFFF inputs from a foam refractory testing event. Targeted analysis, the Total Oxidizable Precursor Assay (TOP Assay), and nontargeted analysis with quadrupole time-of-flight (QTOF) were used to characterize the samples. Over the duration of foam testing, approximately 10.8 kg of total PFASs was measured by TOP Assay in the influent, and 6.3 kg of total PFASs was measured in the effluent; 94 g of PFOS was released in the effluent, apparently from remobilization of historical sources. 1.7% of total PFASs measured in the influent were converted to short chain perfluoroalkyl carboxylates in the effluent. Ten PFAS classes previously reported, including 6:2 fluorotelomer thioether amido sulfonate (6:2 FtTAoS), and 5 PFAS classes newly reported were identified by QTOF. The trickling filter was the only unit operation that resulted in significant gains and losses of individual PFASs, including near complete loss of 6:2 FtTAoS due to transformation. Similar reaction pathways for 6:2 FtTAoS reported in previously published soil and activated sludge microcosm experiments were observed in this WWTP, although a higher yield of perfluoroheptanoic acid was observed.