Formatted Title
The Present and Potential Future of In Situ Activated Carbon PFAS Remedies
Background/Objectives
Injecting powdered or colloidal activated carbon (AC) into the subsurface offers an outcome not obtainable with other current remediation technologies: reducing and even potentially eliminating fluxes of per- and polyfluoroalkyl substances (PFAS) by creating a passive in situ adsorption barrier. This is a potentially powerful technology that can attain orders of magnitude reduction in PFAS mass flux, but the flux reductions are not necessarily permanent, and they may not be sufficient to meet cleanup criteria which are still in development. Moreover, PFAS are not destroyed by in situ adsorption; they are only adsorbed, a process that is reversible.
Approach/Activities
Critical questions remain. First, for how long can in situ AC applications reduce PFAS flux, i.e., the remedy’s longevity? And second, what are potentially viable PFAS flux management options when the remedy reaches the end of its useful life?
Results/Lessons Learned
This presentation surveys the set of questions being evaluated by on-going research programs, including those funded by SERDP and ESTCP and our project ER21-3959 An Investigation of Factors Affecting In Situ PFAS Immobilization by Activated Carbon. Specifically, in this presentation we will examine ongoing experimental programs that are helping build a body of knowledge to estimate the useful lifetime of in situ AC barriers, and to assess the degree of mass flux reduction that can be expected for long-chain PFAS that are likely to be regulated, and short-chain PFAS which may be regulated in the future. The presentation will conclude by considering current data gaps in predicting CAC longevity and future research needs - including approaches for managing PFAS fluxes from the AC adsorption barrier near the end of the barrier’s useful life.
Note: This presentation was an invited talk by US DoD for the Fall 2023 SERDP Symposium, and is being proposed here to further share finding and progress to date.