A Critical Review and Meta-Analysis of the Occurrence and Fate of Per- and Polyfluoroalkyl Substances in Global Wastewater Treatment Plants

This critical review presents a comprehensive meta-analysis on the global occurrence and fate of per- and polyfluoroalkyl substances (PFAS) in wastewater treatment plants (WWTPs). We reviewed over 86 peer-reviewed studies and extracted PFAS concentration data from 717 WWTPs worldwide, encompassing influent, effluent, and residual streams across all treatment stages. A publicly accessible, open-source ArcGIS map was developed to display key information from each study, including geographic location, sampling year, treatment train details, and measured PFAS concentrations. Descriptive and inferential statistical analyses were used to assess occurrence patterns, treatment performance, and transformation trends. Results show strong regional bias in PFAS monitoring, with data concentrated in the U.S., China, and Europe. Despite differences in treatment configuration, conventional WWTPs were generally ineffective at removing PFAS. In WWTPs with secondary treatment, PFOA and PFOS were the most frequently reported and abundant PFAS (>10 ng/L) in aqueous streams, while residuals were dominated by PFOA, PFOS, PFNA, and EtFOSAA. Tertiary systems showed several PFAS had aqueous median concentrations exceeding 10 ng/L. Industrial sources contributed significantly higher influent concentrations than municipal or combined systems. Paired influent and effluent data sets revealed an increase in terminal perfluoroalkyl acids and a decrease in precursors across treatment. Despite these trends, data on precursors, short-chain PFAS, and the impact of specific treatment processes and operating conditions remains limited. This review underscores the critical need for standardized sampling approaches across treatment trains and highlights opportunities to improve PFAS mitigation through targeted monitoring and technology development.