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Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina
Sun, M., E. Arevalo, M. Strynar, A. Lindstrom, M. Richardson, B. Kearns, A. Pickett, C. Smith, AND D. Knappe. Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina. Environmental Science & Technology Letters. American Chemical Society, Washington, DC, 3(12):415-419, (2016).
The USEPA’s recently completed Unregulated Contaminant Monitoring Rule 3 (UCMR3) program and many other state and Regional monitoring efforts have demonstrated that the occurrence of poly- and perfluoroalkyl substances (PFASs) in surface, ground, and drinking water resources is a growing concern for many communities. This manuscript documents the occurrence of PFAS in the largest watershed in North Carolina in 2013 - 2014. Results indicate that legacy PFAS, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), continue to be significant issue. Additionally, many new “replacement” PFAS can now be found in surface and drinking water resources in this basin. Analysis of water samples collected at one community’s drinking water plant shows that conventional treatment processes have a negligible effect on PFAS removal. Additional laboratory-based experiments document the performance of a powdered activated carbon (PAC) adsorbent on the removal of legacy and replacement PFAS from drinking water resources.
Long-chain per- and polyfluoroalkyl substances (PFASs) are being replaced by short-chain PFASs and fluorinated alternatives. For ten legacy PFASs and seven recently discovered perfluoroalkyl ether carboxylic acids (PFECAs), we report (1) their occurrence in the Cape Fear River (CFR) watershed, (2) their fate in water treatment processes, and (3) their adsorbability on powdered activated carbon (PAC). In the headwater region of the CFR basin, PFECAs were not detected in raw water of a drinking water treatment plant (DWTP), but concentrations of legacy PFASs were high. The U.S. Environmental Protection Agency’s lifetime health advisory level (70 ng/L) for perfluorooctanesulfonic acid and perfluorooctanoic acid (PFOA) was exceeded on 57 of 127 sampling days. In raw water of a DWTP downstream of a PFAS manufacturer, the mean concentration of perfluoro-2-propoxypropanoic acid (PFPrOPrA), a replacement for PFOA, was 631 ng/L (n = 37). Six other PFECAs were detected, with three exhibiting chromatographic peak areas up to 15 times that of PFPrOPrA. At this DWTP, PFECA removal by coagulation, ozonation, biofiltration, and disinfection was negligible. The adsorbability of PFASs on PAC increased with increasing chain length. Replacing one CF2 group with an ether oxygen decreased the affinity of PFASs for PAC, while replacing additional CF2 groups did not lead to further affinity changes.