In-situ stabilization of PFAS in groundwater treatability test work

Poly-and-Perfluoroalkyl Substances (PFAS) include persistent, soluble fluorinated compounds that potentially present a risk to human health and the environment. The application of Aqueous Film-Forming Foams (AFFF) containing PFAS, in particular prolonged application at firefighting training areas, has resulted in long-term sources of PFAS leaching into soil and groundwater. The risk from these persistent and bioaccumulative compounds can be mitigated by reducing their mobility in the subsurface. A treatability test program was designed to explore the in-situ stabilization (ISS) of PFAS in soil and groundwater using commercially-available adsorption media. Physical removal via excavation and groundwater extraction with aboveground treatment are the current state of the practice for management of PFAS source zones. ISS presents an alternative the eliminates ex-situ management of PFAS wastes while protecting groundwater from future leaching. ISS consists of the use of augers and cutting tools to mix soil, water, and reagents in place in the vadose and saturated zones. ISS is a highly-effective method for accessing source mass because it homogenizes soil, reduces geological anisotropy, and provides immediate access to soluble PFAS stored in low-permeable strata. The ISS reduces leachability through stabilization with a reagent and may include solidification with cement to encapsulate and reduce permeability. Laboratory tests were conducted with four objectives: Establish basic adsorption performance of selected media for PFAS; test performance as a function of pH; compare performance with and without cement, and obtain leachability data to demonstrate potential long-term stability of in-situ treatment. (author)