Groundwater contaminations by per- and polyfluoroalkyl substances (PFASs) have been identified on a global scale as a result of historical releases of aqueous film-forming foams (AFFF). While these plumes are predominantly treated using granular activated carbon (GAC) and regenerable anionic resins, the emergence of single-use “PFAS-selective” anion exchange resins (AERs) has led to the need for a direct comparison of these adsorbents’ efficacy in treating PFAS. This presentation will describe results from a recently completed field pilot study treating groundwater from a highly contaminated source zone (ΣPFAS: 30-55,000 ng/L) with both regenerable and single-use AERs. Results from the 9-month pilot study demonstrate that single-use AERs provide improved selectivity and capacity for removal of a wide range of PFAS structures compared to both regenerable AERs and GAC, leading to longer operational lifetimes and greater mass removal of PFAS. While treatment of short-chain perfluorocarboxylic acids (e.g., perfluorobutanoic acid, PFBA) was found to be similar among resin types, single-use resins removed sulfonic acid structures (e.g., perfluorooctane sulfonate, PFOS) up to eight times longer than the best regenerable resin prior to analyte detection. Postmortem investigation of the spent resin beds support the mechanism of competitive displacement, where lower-affinity structures like PFBA were displaced by higher-affinity and more abundant sulfonic acid structures like PFOS. The presentation will also discuss how results from the pilot study are being applied to inform a life cycle assessment (LCA) of ion exchange and activated carbon adsorption technologies for PFAS treatment. This analysis highlights the critical importance of site-specific criteria for media replacement or regeneration in selection of an optimal adsorption technology.

Pilot study comparison of regenerable and single-use anion exchange resins for remediation of per- and polyfluoroalkyl substances (PFASs)

ACS Spring 2022

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