Determination of household wastewater PFAS composition and concentrations via sub-sewershed analysis

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in wastewater, challenging water reuse efforts. The PFAS in wastewater are contributed by industrial, commercial, and residential sewerage users. To date, very little is known about the composition and concentration of PFAS discharged by households. We addressed this important knowledge gap by analyzing 24-hour composite wastewater samples obtained for seven consecutive days from three residential sub-sewersheds upstream of wastewater treatment plants. Tap water collected from parks at each sub-sewershed was also analyzed. Although tap water contained some PFAS, we found more analytes and higher concentrations in the residential wastewater samples, suggesting PFAS was introduced at households. The daily ∑PFAS was 10.43 – 49.14 ng/L across the locations. There were no significant (p > 0.05) differences in PFAS concentrations measured on weekdays compared to weekends. PFHxA, PFOA, PFHxS, and PFOS were present in all the samples we obtained, indicating their consistency in consumer products and, thus, residential wastewater. PFOA and PFOS accounted for 12 – 61% of the daily ∑PFAS. We estimated individual PFAS contribution as 2.27 – 10.71 µg/capita/day, with more affluent neighborhoods discharging more PFAS. This is the first study to estimate per capita PFAS using wastewater from upstream household discharge points.