Formatted Title
Bench-Scale Testing of a Novel Soil PFAS Treatment Train for Informed Remedial Planning and Decision-Making
Background/Objectives
Per‐ and polyfluoroalkyl substances (PFAS) have been detected in environmental media across the country, including at many United States Department of Defense (DoD) facilities as a result of historical fire training and suppression activities using aqueous film‐forming foam (AFFF). The DoD is actively investigating the extent of all PFAS impacts arising from storage and use of AFFF and working diligently to mitigate human drinking water exposure. Current estimated costs for managing these sites are substantial. The ubiquity, persistence, mobility, and recalcitrant nature of PFAS requires innovative and iterative remedial technologies that are capable of addressing PFAS impacts—while also minimizing wastes that require further management in a low‐cost, effective, and sustainable manner. This is a critical need for DoD and other impacted sites around the country and world.
Approach/Activities
Bench‐scale batch tests were conducted to assess the potential application of a combined treatment train to separate, concentrate, and destroy PFAS originating from impacted soils and sediments at Schriever Space Force Base arising from historical AFFF. Specifically, a novel treatment train coupling soil washing (for treatment of impacted soil/sediment) with foam fractionation (for treatment of the wash water 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/Lessons Learned
The results show that the AFFF‐impacted sandy soils with low organic content were amenable to treatment via soil washing. However, removal of hydrophobic PFAS, such as perfluorooctane sulfonic acid (PFOS), from the organic‐rich sediments was challenging. Laboratory batch desorption experiments were within a factor of 2 of those generated by soil washing bench studies, suggesting applicability of simple batch tests to reasonably predict the treatment efficacy of soil washing. Long‐chained perfluoroalkyl acids (PFAAs) within the washwater were removed more effectively than short-chain PFAAs in the foam fractionation studies. Addition of a surfactant, such as cetrimonium bromide (CTAB), enhanced foaming but only slightly 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.