Determination of household wastewater PFAS composition and concentrations via neighborhood sampling

The per- and polyfluoroalkyl substances (PFAS) in municipal wastewater-which are typically contributed by the industrial, commercial, and residential sewerage users-present a major challenge for water reuse efforts. However, very little is known about the PFAS profile in household wastewater. We addressed this gap by analyzing 24-hour composite wastewater samples obtained for seven consecutive days from three residential sub-sewersheds upstream of wastewater treatment plants (WWTPs) in Southern California. Compared to tap water from the neighborhoods, we found more analytes and higher concentrations in the household wastewater, suggesting PFAS was introduced into the water cycle at households. The daily ∑₄₀PFAS in household wastewater was 10.4-49.1 ng/L across the sampling campaigns. Despite their phase-out in the US over a decade ago, PFOA and PFOS accounted for 12-61 % of the PFAS in household wastewater, and they exceeded their proposed drinking water maximum contaminant limits (MCLs) on certain days. In addition, PFHxA, PFOA, PFHxS, and PFOS were present in all the samples collected. We determined that individuals within the residential sub-sewersheds contributed 2.3-10.7 µg/capita/day, with individuals in more affluent neighborhoods discharging more PFAS. This is the first study to estimate per capita PFAS loads directly from upstream household discharge points in the United States.