The migration of per- and polyfluoroalkyl substances (PFAS) in shallow groundwater emanating from aqueous film forming foam (AFFF) sources is a critical environmental challenge. While several promising novel approaches for destructive treatment of PFAS are currently under development through on-going Strategic Environmental Research and Development Program (SERDP) projects, continued testing and development is needed before field-scale application and validation of in situ approaches can be considered. To address the pressing need of PFAS plume control at impacted DoD facilities, ex situ treatment technologies involving groundwater extraction coupled with granular activated carbon (GAC) and/or anion exchange resin (AER) are being employed. Passive and long-term in situ PFAS treatment approaches have yet to be demonstrated.

This project will evaluate effective and long-term PFAS plume mitigation by installing a passive in situ permeable adsorptive barrier (PAB) that utilizes AER for PFAS immobilization. The primary objective of this project is to demonstrate the long-term and cost-effective capture and treatment of PFAS emanating from an AFFF source area using a passive in situ PAB that compares two different AERs (regenerable and non-regenerable).

In this demonstration project, the research team will evaluate the efficacy of a pilot-scale PAB funnel and gate system utilizing both regenerable and non-regenerable AERs in two parallel gates to immobilize PFAS in situ. The fundamental concepts supporting this field demonstration are as follows:

1. the utilization of a funnel and gate system to divert groundwater into gates for treatment;
2. the use of AERs for PFAS immobilization;
3. the ability to remove and replace the AERs from the gates, and;
4. ex situ AER regeneration.

The approach is based on the well documented ability of AER to remove both long and short-chained perfluoroalkyl acids (PFAAs), as well as the common co-contaminant, volatile organic compounds (VOCs), in groundwater without frequent replacement or regeneration of the resin. The design and construction of the gates will allow for removal and replacement of the media, as required. During full-scale application of this technology, it is presumed that regeneration of regenerable AER would be performed by removing the resin from the gate and regenerating it either on-site, or sending it off-site for regeneration (and subsequent treatment and/or disposal of the regenerant waste). In the case of the non-regenerable AER, the resin would be removed from the gate and sent off site for proper disposal (e.g. incineration).

There are currently no cost-effective options for the treatment of groundwater plumes containing PFAS. This technology is expected to provide the DoD with a demonstrated in situ, passive, low cost method to mitigate PFAS impacted groundwater in shallow aquifers. There are many different PAB configurations possible for this technology, making it widely applicable at a variety of DoD sites. The funnel and gate PAB approach can be implemented in either high concentration source areas to reduce mass flux, or in larger dilute plumes to protect downgradient receptors and/or mitigate expansion of the plume.