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

Topic Area: 7b. Ex Situ PFAS Treatment Approaches

Formatted Title:

AFFF Transition to Fluorine-Free Foam: Waste Minimization

Background/Objectives:

The 2020 National Defense Authorization Act for the U.S. Department of Defense stipulated the change-out and replacement of PFAS-containing firefighting foams with F3. Other countries and industries are conducting similar activities. A new MILSPEC, MIL-PRF-32725, was published in January 2023 approving the use of F3. As of October 1, 2023, DoD can no longer purchase foam containing greater than 1 ppb PFAS and, as of October 1, 2024, can no longer use PFAS-containing foams. When replacing PFAS-containing foams with F3, the existing infrastructure containing AFFF (e.g., hangar deluge systems, aircraft rescue and fire-fighting vehicles, AFFF supply vessels, etc.), requires cleanout activities to remove residual PFAS and prevent PFAS contamination to new F3. While similar transitions are scheduled to occur over a 10-year period in Europe, the United States is undertaking a 2-year transition. This accelerated schedule has resulted in the rapid development of cleaning protocols that effectively remove PFAS-containing AFFF and clean impacted assets. Rebound of PFAS sorbed onto infrastructure and subsequent re-contamination of F3 foam is a concern. Minimizing waste (rinsate water) generated is also a significant concern for these operations.

Approach/Activities:

First, ECT2 tested multiple cleaning reagents in the laboratory with impacted piping from AFFF-contaminated hangars to evaluate solutions that resulted in greatest PFAS removal. Combinations of solutions were investigated for synergistic effects. In addition to different cleaning reagents, variables such as contact time, temperature variations, and different degrees of turbulence were evaluated for PFAS removal effectiveness. Different sampling strategies and analytical methods were used and evaluated (e.g., wipe tests, collection times for rebound tests, total oxidizer precursor analysis, adsorbable organic fluorine). Rapid (18-24 hour) and semi-extended (week) rebound tests were conducted. Second, ECT2 designed a media-based filtration and PFAS adsorption process that keeps the cleaning reagent in circulation, allowing it to be recycled over multiple passes in order to minimize reagent use and generation of wastewater. Finally, ECT2 piloted the optimized approach at a test site.

Results/Lessons Learned:

The range of effectiveness of various cleaning reagents and their delivery technique will be presented. Data from static soak tests to lab experiments with forward flow and temperature will be presented. Data from the test site, along with challenges encountered and lessons-learned will also be discussed. The longevity of media during recirculation of spent cleaning solution with the optimized cleaning solution will be presented. Realistic timelines and cleaning treatment objectives from the field deployment will be discussed. Options for the ultimate disposition of the treated cleaning reagent will be reviewed.

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Chad Bennett