Aircraft rescue firefighting (ARFF) vehicles are impacted by per- and polyfluoroalkyl substances (PFAS) due to the prolonged application of aqueous film-forming foam. In the process of transitioning to PFAS-free formulations, efficient and standardized methods to remove the residual PFAS from the impacted interior surfaces and prevent environmental impacts would be useful. Cleaning methods must be completed within the system's allowable downtime to avoid exceeding operational limits. However, the elevated PFAS concentration along with the unique self-assembly of PFAS in interior surfaces of these impacted fire suppression systems leads to a potential rebound effect that has made the cleaning procedures a challenging task. The primary objective of this project is to conduct a systematic investigation into removing PFAS from the interior surfaces of fire truck system components, with a specific focus on the sections most significantly impacted by PFAS. Emphasis will be placed on investigating the piping system located beneath the foam tank, as this area has been demonstrated to be significantly impacted by PFAS.

The project will systematically evaluate the cleaning of a fire suppression system. The three main technical objectives of the project include:

• Conducting a comprehensive assessment of the relative distribution and extractability of residual PFAS and precursors within the investigated segment through batch experiments.
• Evaluating the extent of PFAS desorption achievable under a standard two-week timeframe and alternative rinsing/cleaning scenarios.
• Characterizing the supramolecular structures that contribute to PFAS rebound effect across a broad spectrum of PFAS and precursors, using an integrated suspect screening approach alongside targeted analysis.

A systematic understanding of the most PFAS-impacted components of fire suppression systems is critical to advancing the development of a standardized and cost-effective cleaning method for the removal of residual PFAS. This approach not only addresses a pressing operational challenge but also offers substantial potential for widespread application and significant financial benefits. Precedent findings from past ESTCP projects have shown that the traditional practice of cleaning firetrucks with a triple water rinse is generally insufficient for removing residual PFAS and addressing the rebound effect. Additionally, the triple rinse generates a substantial volume of PFAS-impacted waste, which necessitates further disposal or treatment. The information gained from the project will contribute to implementing effective treatment strategies that not only will minimize disposal costs via reducing waste volumes but also address a critical need for infrastructure management. (Anticipated Project Completion - 2028)