Poly- and Perfluoroalkyl Substances in Municipal Wastewater Treatment Plants in the United States: Seasonal Patterns and Meta-Analysis of Long-Term Trends and Average Concentrations

This paper presents an up-to-date meta-analysis assessing per- and polyfluoroalkyl substance (PFAS) concentrations at wastewater treatment plants (WWTPs) as well as changes over time. PFAS concentrations were compiled for WWTPs in the United States from peer-reviewed studies, technical reports, and original data. Perfluorooctanoic acid (PFOA) increased by an average of 6.0 +/- 1.6 ng/L from the influents to the effluents of WWTPs, but perfluorosulfonic add (PFOS) did not significantly change, indicating sorption to sludge is offset by biotransformation of precursor compounds. The occurrence of individual PFAS may vary temporally; for example, perfluoropentanoic add correlated weakly with seasonal temperatures at a site in Virginia. Wastewater effluent PFOA concentrations decreased at a site in Nevada from 2012 to February 2020 but appeared to increase during the COVID-19 pandemic. Effluent PFOA also declined nationally from 1999 to 2020 by similar to 13% per year. Nevertheless, the national mean PFOA concentration was 8.4 +/- 0.4 ng/L in data collected from 2013 to 2020 with outliers omitted, indicating persisting low-level occurrence. This would equate to 383 +/- 20 kg of PFOA per year continuing to enter the environment via WWTP effluents.

Automated summary

This paper presents a meta-analysis that assesses the concentrations of per- and polyfluoroalkyl substances (PFAS) in wastewater treatment plants (WWTPs) and their changes over time. The study found that while the concentration of perfluorooctanoic acid (PFOA) increased, the concentration of perfluorosulfonic acid (PFOS) did not significantly change, suggesting that the sorption to sludge is offset by biotransformation of precursor compounds. The occurrence of individual PFAS may vary temporally, and the concentration of PFOA in wastewater effluent showed a decrease in some locations but appeared to increase during the COVID-19 pandemic. However, overall, the concentration of PFOA remains persistently low, with approximately 383 kg of PFOA entering the environment via WWTP effluents annually.