Assessing PFAS and Their Precursor Transformation in a Landfill Leachate-Impacted Wastewater Treatment Plant

Despite growing concern over polyfluoroalkyl and perfluoroalkyl substances (PFAS), comprehensive evaluations of their behavior in wastewater treatment plants (WWTPs) influenced by landfill leachate remain limited. This study introduces a novel, integrated framework to investigate the fate, transformation, and persistence of PFAS across various treatment stages within a full-scale WWTP uniquely impacted by a mixture of domestic wastewater and industrial landfill leachate. By combining advanced targeted analysis using USEPA Draft Method 1633 with extractable organic fluorine (EOF) quantification and total oxidizable precursor (TOP) assays, this approach offers a comprehensive, multidimensional characterization of PFAS behavior. The USEPA Draft Method 1633 revealed influent and effluent PFAS concentrations ranging from 432 to 727 and 356 to 558 ng/L, respectively, with overall removal efficiencies of 6%–25% across three sampling events. Post-TOP assay results showed that PFAS concentrations increased approximately twofold in influent (637–1205 ng/L) and 1.5-fold in effluent (600–927 ng/L), indicating the presence of oxidizable PFAS precursors. Additionally, targeted PFAS accounted for only 12%–20% of total EOF in influent and 15%–25% in effluent samples, demonstrating the substantial presence of unidentified fluorinated compounds beyond routine analysis. Moreover, significant PFAS partitioning to sludge was quantified, with total concentrations reaching ~17,000 ng/kg in untreated sludge and ~19,000 ng/kg in final biosolids, underscoring the potential for terrestrial redistribution via land application. Compared with earlier works that narrowly focused on known PFAS compounds or specific treatment technologies, this study delivers a comprehensive, multi-method perspective on PFAS behavior, precursor transformation, and environmental release potential. These insights advance the understanding of PFAS fate in complex wastewater matrices and emphasize the need for expanded monitoring strategies to inform future regulatory and remediation efforts.