Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7p. PFAS: Groundwater Treatment Case Studies

Formatted Title:

Aqueous Film-Forming Foam (AFFF) Source Area Groundwater Per- and Polyfluoroalkyl Substances (PFAS) Treatment with Foam Fractionation Bench- and Pilot-Scale Demonstration

Background/Objectives:

Many sites are impacted by per- and polyfluoroalkyl substances (PFAS), primarily resulting from the historical use of aqueous film forming foam (AFFF). At fire training areas (FTAs), PFAS are often found in soil and groundwater. For comprehensive treatment of impacted groundwater from FTAs, a treatment train of conventional treatment technologies may be required to achieve target treatment goals. The operational costs of running treatment technologies using sorptive media such as granular activated carbon (GAC) and ion exchange (IX) resins to remove PFAS can be excessive. One potential option is to the application of foam fractionation with ozofractionative catalyzed reagent addition (OCRA), a patented process by Evocra (Australia). This process is able to simultaneously treat PFAS and organic and inorganic co-constituents via multiple mechanisms, including foam fractionation, advanced oxidation processes (AOPs), metal precipitation, flotation and sedimentation. Foam fractionation with OCRA includes a series of chambers in which fine gas bubbles are sparged through PFAS-impacted water to facilitate gas-liquid interface partitioning of dissolved PFAS into a foam fraction, which is collected from the surface of the vessels as a PFAS concentrate. The objective of this case study was to perform bench-scale testing and an onsite foam fractionation temporary slipstream pilot demonstration test on PFAS-impacted water from an existing groundwater extraction well from an aqueous film-forming foam (AFFF)-impacted source zone at an east coast Naval Air Station.

Approach/Activities:

Bench-scale treatability testing was completed at the Arcadis U.S., Inc. (Arcadis) treatability laboratory, located in Durham, North Carolina, prior to onsite pilot demonstration. Water from the site was used during bench testing to validate the process and determine proper operating parameters. Analytical methods included Draft USEPA Method 1633 for groundwater and a modified USEPA OTM-45 method for air. The results from the bench-scale testing will be discussed to provide the necessary information to design a successful onsite pilot demonstration. The next phase of the demonstration is the deployment of the system to the field for approximately one month at the end of 2023, where performance will be monitored for a variety of parameters, including flowrate, total volume treated, PFAS removal, foam production, and other operational parameters.

Results/Lessons Learned:

The focus of this demonstration is to validate this foam fractionation technology with PFAS-impacted groundwater from a source area extraction well. Batch treatability testing of site groundwater showed significant removal of PFAS in groundwater with more than 20 kg of PFAS captured in the foam generated by fractionation (or approximately 14% by volume with regards to the foam balance). Results showed significant reduction (99% reduction in PFOS and PFOA concentrations) in the treated effluent sample concentrations over the course of the test and definitive evidence of PFAS concentrating into the foam phases. The addition of a reagent is required due to the low-foaming water at the site. Implications of both the bench and pilot demonstration study will also be presented.

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Nicole Carter