Residential Wastewater as a Major Source of Per- and Polyfluoroalkyl Substances to Municipal Wastewater

Identification of major sources of per- and polyfluoroalkyl substances (PFAS) in wastewater requires comprehensive evaluation, as wastewater is a pathway for a wide range of PFAS products in use, and the PFAS class includes thousands of compounds. We applied both EPA Method 1633 and the total oxidizable precursor (TOP) assay to quantify PFAS in municipal wastewater and upstream sewers in the San Francisco Bay region. Evaluation of PFAS in residential wastewater discharges (mean sum of TOP PFAS = 287 ng/L, n = 17) was comparable to average PFAS levels in influent of the corresponding four wastewater treatment plant (WWTP) receivers. First-order calculations estimated that at the three WWTPs that receive over 80% of influent flows from residential customers, residential customers accounted for a majority of estimated PFAS mass loadings entering the WWTP. Additionally, high levels of PFAS were observed in wastewater discharges from industrial laundries (mean = 11,000 ng/L, n = 9) compared to WWTP influent. PFAS levels quantified in wastewater influent, biosolids, and residential wastewater discharges were up to an order of magnitude greater using the TOP assay compared to EPA Method 1633, demonstrating the significant presence of unknown PFAS precursors.