Topic Area: 4c. Activated Carbon-Based PFAS Treatment Technologies

Formatted Title:

Over Three Years of Data from a Large Full-Scale Colloidal Activated Carbon PFAS Groundwater Remedy

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) are considered an emerging contaminant in groundwater at many military and industrial sites. Aqueous film-forming foam (AFFF), used to extinguish fires, is a major source of PFAS in groundwater worldwide. PFAS has been shown to be effectively removed from groundwater using several different types of adsorptive media, including activated carbon. Colloidal activated carbon (CAC) is a remediation product composed of very fine particles of activated carbon suspended in polymer that can be injected into the subsurface to facilitate in situ remediation of PFAS. After injection, the CAC binds to the aquifer matrix and serves as an in situ filter to remove PFAS from groundwater as it comes in contact with the activated carbon particles. This project was performed at a former Fire Training Area (FTA) where groundwater is impacted with PFAS from historical AFFF usage. Elevated PFAS concentrations were identified (generally greater than 10 parts per billion) in a shallow perched aquifer. The subsurface consists of a permeable industrial fill and sand, underlain by a continuous clay layer. Due to a regulatory driver, the remedial objective for the site was to reduce PFAS groundwater concentrations that were migrating from the perched aquifer to a nearby surface water body.

Approach/Activities:

The approach for achieving the remedial objective was to install an in situ permeable treatment barrier perpendicular to groundwater flow along the perimeter of the FTA, upgradient of the surface water body. Based on results of a brief pilot study, a full-scale CAC remedy was designed and rapidly implemented. The full-scale approach consisted of injecting over 292,000 pounds of CAC into over 650 injection points to create a 1,625 foot-long barrier perpendicular to groundwater flow. CAC loading in certain areas was modified based on the presence of co-contaminants. To date, this is the largest full-scale CAC barrier installed to treat PFAS in groundwater.

Jim Buzzell

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Over Three Years of Data from a Large Full-Scale Colloidal Activated Carbon PFAS Groundwater Remedy