Practical limits of current technologies in removing per- and polyfluoroalkyl substances from fire suppression systems

Several commercial products have been broadly marketed for their effectiveness in removing residual PFAS from AFFF-impacted fire suppression systems. However, a comprehensive assessment of their effectiveness in mitigating long-term PFAS rebound following the initial cleaning has not been reported. Herein, batch and flow-through experiments were conducted to interrogate the overall effectiveness of four different cleaning solutions in removing residual PFAS from AFFF-impacted stainless steel pipes from a fire suppression system. Advanced surface imaging techniques were also employed to correlate with bench-scale testing results and to provide insights into potential PFAS rebound mechanisms. Results presented herein demonstrate that complete removal of PFAS from AFFF-impacted fire suppression systems is extremely difficult to achieve for all four cleaning solutions examined in this study. The PFAS rebound behavior observed was likely attributable to PFAS supramolecular assemblies accumulating on the pipe surfaces. Because PFAS rebound following cleanout of AFFF-impacted fire suppression systems is likely inevitable, there needs to be an understanding of the practical limits to which impacted fire suppression system cleanout can be achieved. Improved insights into the dissolution mechanisms and the rate of dissolution of supramolecular formations will be key to improving PFAS decontamination processes and decontamination of materials/equipment impacted by AFFFs.