Bench‐scale testing of a novel soil PFAS treatment train for informed remedial planning and decision‐making

Abstract

Bench‐scale batch tests were conducted to assess the potential applicability of a combined separation/concentration/destruction treatment train to address soils and sediments impacted by per‐ and polyfluoroalkyl substances (PFAS) contamination at Schriever Space Force Base with historic aqueous film‐forming foam (AFFF). Specifically, a novel treatment train coupling soil washing (for treatment of impacted soil/sediment) with foam fractionation (for treatment of the wash water [WW] generated during soil washing) and electrochemical oxidation (ECO, for treatment of the foam fractionate generated during foam fractionation) was evaluated at the bench scale using site‐specific materials. Results presented herein show that the AFFF‐impacted sandy soils with low organic content were amenable to treatment via soil washing. However, the removal of hydrophobic PFAS, such as perfluorooctanesulfonic acid (PFOS), from the organic‐rich sediments was challenging. Results from batch desorption experiments were within a factor of 2 of those generated by soil washing bench studies, suggesting that simple batch tests can potentially be used to reasonably predict the treatment efficacy of soil washing. Long‐chained perfluoroalkyl acids (PFAAs) within the WW were removed more effectively in the foam fractionation studies as compared to short‐chain PFAAs. Addition of a surfactant, such as cetrimonium bromide (CTAB), enhanced foaming but only marginally improved the treatment of short‐chained PFAAs and in some cases inhibited PFOS removal. ECO reduced PFAS concentrations in the foam fractionate generated during foam fractionation by several orders of magnitude. However, generation of unwanted byproducts may warrant further treatment and/or disposal. Overall, results from this study provide a novel data set highlighting the site‐dependent nature of these PFAS remedial technologies and how simple, low‐cost bench tests can be reliably leveraged for informed decision‐making during PFAS remedial planning.