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

Identification\nof major sources of per- and polyfluoroalkyl substances\n(PFAS) in wastewater requires comprehensive evaluation, as wastewater\nis a pathway for a wide range of PFAS products in use, and the PFAS\nclass includes thousands of compounds. We applied both EPA Method\n1633 and the total oxidizable precursor (TOP) assay to quantify PFAS\nin municipal wastewater and upstream sewers in the San Francisco Bay\nregion. Evaluation of PFAS in residential wastewater discharges (mean\nsum of TOP PFAS = 287 ng/L, <i>n</i> = 17) was comparable\nto average PFAS levels in influent of the corresponding four wastewater\ntreatment plant (WWTP) receivers. First-order calculations estimated\nthat at the three WWTPs that receive over 80% of influent flows from\nresidential customers, residential customers accounted for a majority\nof estimated PFAS mass loadings entering the WWTP. Additionally, high\nlevels of PFAS were observed in wastewater discharges from industrial\nlaundries (mean = 11,000 ng/L, <i>n</i> = 9) compared to\nWWTP influent. PFAS levels quantified in wastewater influent, biosolids,\nand residential wastewater discharges were up to an order of magnitude\ngreater using the TOP assay compared to EPA Method 1633, demonstrating\nthe significant presence of unknown PFAS precursors.