Their are many fire suppression systems impacted by residual per-and polyfluoroalkyl substances (PFAS), as a result of the use of Class B foams such as aqueous film-forming foam (AFFF). Amphiphilic PFAS are known to self-assemble in multiple bilayers to coat surfaces at liquid:solid interfaces, forming a waterproof coating. The objective of this project was to optimize procedures for cleaning of fire suppression infrastructure to remove aggregated PFAS, initially at the laboratory scale and then at field scale. At the laboratory scale, the formulation of a cleaning agent, soaking times and pressure washing were examined for residual PFAS removal efficiency. At the field scale, flushing curves were developed for PFAS removal in an aviation rescue and firefighting (ARFF) vehicle and a fixed fire suppression system.

This project optimized a protocol for the removal of self-assembled layers of PFAS from fire suppression systems and associated infrastructure using Fluoro Fighter™ cleaning agent. Fluoro Fighter™ simplifies the foam transition process by removing PFAS from foam-wetted surfaces, keeping it from impacting new foams, preventing time-consuming rework, and avoiding widespread asset replacement needs. The non-flammable, biodegradable Fluoro Fighter™ is safe for handling, user exposure, and transportation.

Critical Findings

The following critical findings were developed:

• Results from the fixed system cleaning at Naval Air Station Willow Grove and the ARFF vehicle cleaning at Tyndall Air Force Base demonstrated approximately 88 g and 67 g of total measured PFAS mass post-total oxidizable precursor (TOP) assay was removed during the cleaning activities, respectively.
• For both the ARFF and the fixed system, the final water flush demonstrated a ~99% reduction in total measured PFAS concentrations post-TOP assay compared to the baseline water flush.
• For the fixed system, the perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) using Environmental Protection Agency Method 537.1 (modified) prior to use of TOP assay (“pre-TOP”) concentrations in the final water rinse were both below the limit of quantification (LOQ) for the fixed system, but the success criteria of 40 nanograms per liter (ng/L) could not be determined based on the high LOQs in the samples (LOQ = 50 micrograms per liter [µg/L] for PFOA and 100 µg/L for PFOS).
• For the ARFF vehicle, the PFOS and PFOA pre-TOP assay concentrations in the final water rinse were 4,660 ng/L and 191 ng/L, respectively.
• Laboratory work showed Fluoro Fighter™ removed significantly more PFAS from the surface of AFFF concentrate piping compared to water or methanol (p<0.05).
• Laboratory work also showed that Fluoro Fighter™ removed significantly more PFAS from the surface of AFFF concentrate pipe compared to extractions at room temperature.
• Results demonstrated 99.2% lower PFAS concentrations in PFAS-free firefighting formulation following exposure to a fixed fire suppression system cleaned with Fluoro Fighter™ compared to an uncleaned system (1,500 µg/L unclean vs 12 µg/L clean ∑PFAS measured post-TOP assay).
• Anticipated cost drivers that should be considered in selecting the technology for future implementation are regeneration of cleaning agent, scalability, and analytical verification.

Fluoro Fighter™ utilization has the ability to remove additional PFAS build-up in firefighting systems compared to water flushing, ultimately minimizing rebound of PFAS into new firefighting agents. Fluoro Fighter™ has the potential to reduce the impact of chemicals of concern on DoD installations with a focus on a cost-effective, field-ready solution that supports installations to remain mission-capable while safeguarding critical defense infrastructure and the workforce. (Project Completion - 2024)