Cleaning AFFF-impacted Fire Suppression Systems: Comparing Triple Water Rinse Versus TRS Group Method

Estimated reading time: 3 minutes

TRS Group (TRS), a Parsons company, performs cleanouts of mobile and fixed fire suppression systems that have used aqueous film-forming foam (AFFF) to extinguish fuel and oil fires. AFFF can contain up to 6% per- and polyfluoroalkyl substances (PFAS). Because state and federal agencies are limiting the allowable PFAS concentrations in the environment to extraordinarily low levels, the firefighting community is replacing AFFF with fluorine-free foams (F3), which requires not only draining the AFFF from fire suppression systems, but also cleaning the wetted surfaces.

Unfortunately, PFAS form coatings that are resistant to removal and do not dissolve readily in water. Studies have shown that rinsing with water leaves large quantities of PFAS behind (Lang et al. 2022).

Triple Rinse Versus The TRS Method

The generic steps of AFFF removal and cleanout follow:

• Removal of AFFF concentrate
• Physical rinsing of foam tanks, pipes, pumps, etc.
• Rinsing of the wetted surfaces using a suitable liquid
• Treatment or disposal of the rinsate and other generated waste

TRS compared the effectiveness of a triple water rinse (3x Rinse) to our approach. We cleaned an aircraft rescue and firefighting (ARFF) vehicle at a major international airport using established 3x Rinse methodology and then treated the same vehicle using our method. After each cleaning, we filled the foam tank with water, circulated it throughout the system, let it equilibrate, took samples, and then analyzed for specific PFAS compounds. The graphs below show PFAS concentrations after the 3x Rinse and TRS’s approach.

The 3x Rinse reduced the concentration of PFOA in the ARFF’s AFFF storage tank (bottom graph); however, there was no reduction in total PFAS concentrations (upper graph). The dominant compound in the 3x Rinse water was 6:2 fluorotelomer sulfonic acid (6:2 FTS), with its concentration actually increasing.

The TRS approach reduced total PFAS concentration by more than 99%. Furthermore, we saw 6:2 FTS concentration reductions of 99.3% and we achieved non-detect levels for PFOA and PFOS.

References

Johnsie R. Lang, Jeffery McDonough, T.C. Guillette, Peter Storch, John Anderson, David Liles, Robert Prigge, Jonathan A.L. Miles, Craig Divine (2022): Characterization of per- and polyfluoroalkyl substances on fire suppression system piping and optimization of removal methods. Chemosphere 308, 136254.idues inside the vehicles cannot be removed effectively using water alone.