Recent studies have documented widespread contamination of drinking water sources throughout the U.S. by per- and polyfluoroalkyl substances (PFASs), due to their presence in aqueous film-forming foam (AFFF) used to extinguish liquid fuel fires (e.g., from aircraft crashes). Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) concentrations measured in groundwater near fire training areas routinely exceed EPA health advisory levels (HALs = 70 ng/L combined) by 1000x or more. Thus, there is growing interest in developing treatment technologies for PFAS-impacted water sources. This has proven challenging because PFOA and PFOS are highly recalcitrant and the conventional approach to treatment (i.e., activated carbon) has proven to be very costly. Previous research has shown that UV light combined with iodide or sulfite photosensitizers generates hydrated electrons (e<sub>aq</sub><sup>-</sup>), potent reductants capable of degrading PFOA and PFOS. However, the efficacy of treating complex PFAS mixtures in AFFF remains unknown. In this work, a UV/sulfite process was utilized to study treatment of AFFF solutions (60,000-fold dilution). Reactions were performed in a sealed immersion well reactor (575 mL) outfitted with an 18 W low pressure mercury lamp light source (λ=254 nm) and sodium sulfite (1-20 mM). The effects of sulfite dosage and AFFF concentration on treatment were investigated. Transformation of individual PFASs were tracked using LC-QToF-MS and defluorination was also calculated (ratio of fluoride released and total fluorine). Results show that treatment with 10 mM sulfite yields 54% defluorination, and both perfluoroalkyl carboxylates (e.g., PFOA) and long-chain perfluoroalkyl sulfonates (e.g., PFOS) are readily degraded. Thus, results indicate that UV/sulfite treatment is a promising strategy for treating AFFF-impacted groundwater to meet the EPA HALs. Insights and challenges for future technology development will also be discussed.

Destruction of per- and polyfluoroalkyl substances (PFASs) in water sources impacted by aqueous film-forming foam (AFFF) using a photoreductive UV/sulfite process

255th National Meeting (2018)

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