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

Formatted Title:

Chemometric and Modeling Analysis of PFAS Compounds Following Colloidal Activated Carbon Injection

Background/Objectives:

This presentation describes the emplacement methodology and interpretation of monitoring results of a pilot-scale colloidal activated carbon injection (PlumeStop™) designed to reduce mass discharge of per- and polyfluoroalkyl substances (PFAS) in groundwater. Historic usage of aqueous film-forming foam (AFFF) has created impacts to shallow groundwater at NASA’s Kennedy Space Center, which have the potential to migrate to surrounding surface waters. The pilot study created a shallow permeable reactive barrier (PRB) within an area impacted with elevated PFAS concentrations and potential surface water discharge risks. In addition to evaluating the overall success of the PRB, this presentation will evaluate the occurrence of back diffusion and changes in PFAS chemical distribution downstream of the PRB.

Approach/Activities:

The pilot test area was thoroughly characterized for soil type, vadose zone PFAS and total organic carbon (TOC) concentrations, groundwater PFAS and TOC concentrations, groundwater chemical/geochemical parameters, seepage velocity, and PFAS mass flux prior to PRB emplacement. The colloidal activated carbon PRB was applied downgradient of a known AFFF source area containing select PFAS concentrations more than 1,000 nanograms per liter (ng/L). Soils at the site were predominantly fine to medium poorly graded sands from ground surface to 50 feet below land surface (bls). The average water table at the site was approximately 3 feet bls. The PRB was installed from 3 to 13 feet bls and oriented perpendicular to the groundwater flow direction. The colloidal activated carbon was injected using direct push technology (DPT) and digital pumping equipment at an average flowrate of approximately 2.5 gallons per minute (gpm) and an average pressure of approximately 11 pounds per square inch (psi). A total of 4,400 pounds of PlumeStop™, diluted to a 22,000 mg/L solution, was injected at 12 locations to create a PRB approximately 35 feet long and 10 feet wide. The amendment distribution was verified during the injections by measuring groundwater parameters at adjacent monitoring wells and piezometers, and immediately after the injections by observing soil cores.

Deda Johansen

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Chemometric and Modeling Analysis of PFAS Compounds Following Colloidal Activated Carbon Injection