Organofluorines in Wastewater

B.J. Ruyle, E.H. Pennoyer, S. Vojta, J. Becanova, M. Islam, T.F. Webster, W. Heiger-Bernays, R. Lohmann, P. Westerhoff, C.E. Schaefer, E.M. Sunderland, High organofluorine concentrations in municipal wastewater affect downstream drinking water supplies for millions of Americans, Proc. Natl. Acad. Sci. U.S.A.122 (3) e2417156122, https://doi.org/10.1073/pnas.2417156122 (2025)

The article below is to a large extent excerpted from the above cited article.

Since the 1940s, humans have synthesized tens of thousands of organofluorine chemicals that are extensively used in products such as refrigeration, fluoropolymers, pharmaceuticals, agrochemicals, and nonstick and greaseproof coatings. A subset of organofluorine compounds, per- and polyfluoroalkyl substances (PFAS), has garnered intense interest in recent years because they have been associated with numerous adverse effects on the health of humans and wildlife; and recently been regulated by the U.S. Environmental Protection Agency (EPA). In 2024, the US Environmental Protection Agency (EPA) finalized federal regulations for six PFAS in drinking water: PFOS and PFOA and the hazardous mixture of PFBS, perfluorohexane sulfonate (PFHxS), perfluorononanoate (PFNA), and hexafluoropropylene oxide dimer acid (HFPO-DA/GenX)

Municipal wastewater is increasingly being used to supplement drinking water supplies. With an environmental buffer, such as a lake, river, or a groundwater aquifer, before the water is drawn to and treated at a drinking water treatment plant is called indirect reuse. There is also direct potable reuse where the wastewater stream is simply treated further and sent to the drinking water distribution system. The contaminants in the wastewater are a growing concern that is being highlighted by the appearance of PFAS in the EPA mandated testing of drinking water supplies.  Some municipal water supplies may be receiving PFAS contaminants from the wastewater used to supplement water supplies.

Municipal wastewater treatment facilities receive PFAS from diverse domestic and industrial sources and have been thought to be associated with impaired drinking water quality across the United States. To better understand the magnitude and composition of aqueous organofluorine discharged from large wastewater treatment facilities, sampling was necessary and the above cited study does just that. 

The complexity of analytical methods used to detect and quantify organofluorine in wastewater has in the past limited our understanding of its prevalence. Most wastewater measurements have focused on a few intensively studied PFAS. However, recent work using bulk organofluorine measurements such as extractable organofluorine found the presence of large quantities of unknown organofluorine.

Prior work on wastewater biosolids suggests that pharmaceuticals may account for a substantial fraction of the unknown extractable organofluorine mass. The researchers constructed a mass budget for extractable organofluorine  measured in the wastewater influent and effluent samples from eight large wastewater treatment plants. These plants were chosen because they use similar treatment technologies and are similar in sizes as those serving 70% of the US population. Measurements of extractable organofluorine  taken  in this study were combined with the DRINCS model to quantify wastewater impacts on downstream drinking water sources. Results of this work provide estimates of the number of drinking water facilities (and their service populations) which would need to mitigate upstream wastewater-derived organofluorine sources and/or implement advanced drinking water treatment to prevent exposures to toxic substances.

The sum of targeted PFAS, precursors, and fluorinated pharmaceuticals explains all of the EOF in aqueous influent and effluent samples in this study, within commonly accepted uncertainty bounds (±30%) in all but two samples. What they found was that extractable organofluorine  was poorly removed during wastewater treatment.  

All eight wastewater treatment plants in this study had primary (physical screening/settling) and secondary (microbial processing of labile organic matter) treatment. Half of the facilities had advanced tertiary treatments including ozonation, activated carbon filtration, and ultrafiltration. However, they found a maximum of 24% decline in aqueous-phase extractable organofluorine  compared to influent and no significant differences between aqueous influent and effluent concentrations 

The six EPA regulated PFAS accounted for an average of 8 ± 8% of the extractable organofluorine  in the wastewater treatment plant effluent samples. PFOS and PFOA exceeded federal standards in 63% of the effluents, while the hazardous PFAS mixture standard was not exceeded in any effluent. The greatest exceedance at any facility was observed for PFOA (six times greater than the regulation). At that site, environmental dilution with contaminant-free water or drinking water treatment up to a factor of six would be needed to prevent downstream concentrations that exceed regulatory standards. This could be very problematic for wastewater treatment streams like UOSA which can during dry periods be a significant portion of the flow into the Occoquan Reservoir. Testing has found that public drinking water not only from the Occoquan Reservoir, but also in Newport News, Norfolk, Roanoke and Charlottesville exceed the EPA regulatory limits. This impacts 29% of Virginians. 

Chemical regulation in the United States typically considers risks associated with individual chemicals rather than the complex mixtures present in wastewater effluent or the environment. But the world has changed as more and more of the water we drink is either directly or indirectly recycled. This poses a challenge for regulating PFAS, pharmaceuticals, and other organofluorine compounds because there are potentially tens of thousands of these chemicals currently in use. Most organofluorine compounds lack analytical standards needed for routine environmental measurements and for evaluating toxicity. It may be time to reconsider the water treatment requirements for water reuse both direct and indirect.