The objective of this project is to demonstrate and validate amendment-enhanced in situ flushing technique as a cost-effective mass removal technology that can be applied to treat soil in source zones impacted by per- and polyfluoroalkyl substances (PFAS). This project seeks to protect soil and groundwater resources by desorbing PFAS from source areas and extracting the desorbed PFAS for treatment in the aboveground treatment system.

In a recent bench-scale treatability study, Tetra Tech, Inc. demonstrated the applicability of the amendment enhanced soil-flushing technique using impacted soil. An optimization study will be conducted to evaluate PFAS mass removal efficiencies using a combination of amendments and concentrations, to minimize the volume of the amendment-enhanced flushing solution, and to compare the application with only water used as flushing solution.

In situ flushing techniques have been previously used at several sites to desorb or solubilize chemicals in situ and is similar in concept to surfactant-enhanced aquifer remediation. The technology involves the injection of an aqueous solution into a source area to desorb the chemicals and then extraction of the resulting fluid for treatment or disposal.

This project primarily focuses on improving the efficacy of in situ flushing to treat source zone soil impacted by PFAS by adding the novel mix of biodegradable and non-toxic amendments in the flushing solution. Three different types of amendment (i.e., polymer, active desorber, and biosurfactant) will be added to the flushing solution to enhance PFAS desorption. The feasibility of biodegradable amendments that exploit multiple, complementary desorption mechanisms (e.g., electrostatic interactions, solubilization, etc.) for PFAS will be validated. The project will demonstrate that the amendment enhanced flushing will result in considerable desorption of PFAS from soil as compared to water flushing alone. Project success will include demonstrating biodegradability of the flushing solution in addition to removal of considerable amount of PFAS mass from soil.

This field demonstration will demonstrate a cost-effective soil treatment technology that can be readily applied to remove PFAS from soils in source zones at a lower cost than in situ thermal and ex situ soil washing treatment. Successful application of a novel in situ soil flushing technique will desorb PFAS from source zones, thereby preventing the spread and decreasing the persistence of a chemical plume. More importantly, this technique can be combined with ex situ groundwater treatment, resulting in the reduction of overall treatment costs and maximizing the potential beneficial reuse of treated materials. This project will advance the technology readiness for large scale application, with anticipated commercial availability for deployment. Such advancements in large-scale PFAS remediation and destruction will contribute to sustainment of force readiness and the operational capacity of the defense industrial base, preventing disruptions to production and supply chains. (Anticipated Project Completion - 2026)