From Home to Hazard: Tracking PFAS From Residential Wastewater Through Wastewater Treatment Sludge to Sludge-Derived Ash

Poly- and perfluoroalkyl substances (PFAS), commonly known as “forever chemicals,” are highly persistent environmental contaminants widely present in municipal wastewater due to their extensive use in consumer products and industrial applications. This study quantitatively tracks PFAS occurrence, transformation, and fate across three municipal wastewater treatment plants (WWTPs A, B, and C; design capacities: 3, 0.8, and 13 MGD). Composite sampling revealed that influent ∑PFAS ranged from 186 to 365 ng/L, while effluent ∑PFAS ranged from 247 to 361 ng/L, reflecting increases of 4%–23% attributable to precursor transformation during treatment. For grab samples, influent ∑PFAS spanned 157–234 ng/L, with effluent values of 189–322 ng/L, representing site-specific variation from −13% to +25%. The total oxidizable precursor (TOP) assay results indicated substantially higher ∑PFAS due to precursor oxidation: influent values increased to 424–882 ng/L (2.1–3 times higher than target analysis) and effluent rose to 565–901 ng/L (up to 4 times higher). Sludge samples contained ∑PFAS of 3282–5324 ng/kg, an order of magnitude above aqueous samples and dominated by short-chain PFCAs (70%–85%). However, incineration demonstrated an approximate 99% reduction in PFAS content in sludge-derived ash, confirming its potential as an effective destruction method. The results thus emphasize WWTPs as secondary sources of PFAS contamination and the critical need for enhanced regulatory monitoring and advanced treatment strategies to mitigate their environmental and public health risks.