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EVALUATING THE LONGEVITY OF A PFAS IN SITU COLLOIDAL ACTIVATED CARBON REMEDY
Carey, G.R., R. McGregor, A.L.-T. Pham, B. Sleep, and S.G. Hakimabadi.
Remediation 29:17-31(2019)

The remediation of per- and polyfluoroalkyl substances (PFAS) by injection of colloidal activated carbon (CAC) at a contaminated site in Central Canada was evaluated using various visualization and modeling methods. Radial diagrams were used to illustrate spatial and temporal trends in perfluoroalkyl acid (PFAA) concentrations, as well as various redox indicators. To assess the CAC adsorption capacity for PFOS, laboratory Freundlich isotherms were derived for PFOS mixed with CAC in two solutions: (1) PFOS in a pH 7.5 synthetic water that was buffered by 1 mM NaHCO3; and (2) a groundwater sample (pH = 7.4) containing PFAS from a former fire-training area in the United States. A mass balance approach was derived to facilitate the numerical modeling of mass redistribution after CAC injection, when mass transitions from a two-phase system (aqueous and sorbed to organic matter) to a three-phase system that also includes mass sorbed to CAC. An equilibrium mixing model of mass accumulation over time was developed using a finite-difference solution and was verified by intermodel comparison for prediction of CAC longevity in the center of a source area. A 3D reactive transport model (ISR-MT3DMS) was used to indicate that the CAC remedy implemented at the site is likely to be effective for PFOS remediation for decades. This paper is Open Access athttps://onlinelibrary.wiley.com/doi/10.1002/rem.21593.



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