Lessons Learned from Three Years of Full-Scale PFAS Plume Management and Liquid GAC Groundwater Treatment

Background. Site FT-02 is a former fire training area (FTA) that was active from 1958 through 1991 at former Wurtsmith AFB, in Oscoda, Michigan. Historical VOC remedial actions at site have included soil vapor extraction (SVE) to treat source area and smear-zone soils (2001–2010), in situ anaerobic biodegradation (IAB) (2012-2014) via nitrate degradation to treat smear-zone soils, and ongoing plume perimeter monitored natural attenuation. On 20 April 2015, a groundwater pump and treat (P&T) system was activated to capture the PFOA/PFOS plume with the extracted groundwater being treated by liquid granular activated carbon (LGAC) to below PFOA and PFOS discharge objectives of 0.04 and 0.02 micrograms per liter [µg/L]), respectively.

Results/Lessons Learned. At the time of the FT-02 treatment system design and installation, much was unknown about PFOA and PFOS plume behavior, and/or the LGAC treatment of these compounds, and the contaminants remain classified as an emerging contaminate. Further delineation of the plume characteristics have shown that the PFOA/PFOS plume is concentrated near the water table surface. Passive Flux meters (PFM) have been deployed to evaluate their applicability to PFOA/PFOS measurement as well as their correlation to groundwater concentrations. Groundwater samples have recently been analyzed by the total oxidable precursor (TOP) assay, with results indicating that PFOA/PFOS account for only about ~30% of total PFAS impact to the LGAC system. To date there have been eleven LGAC exchanges, with seven occurring since Bay West took over management of the FT-02 treatment system on 01 Sept. 2016. Results of the LGAC treatment effectiveness have indicated that full scale performance is significantly less than performance estimated by the initial accelerated column testing