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Case Studies

Firetruck Cleaning and Simultaneous PFAS Destruction using PFASigator®

Enspired Solutions conducted a pilot demonstration using our groundbreaking PFAS destruction equipment, the PFASigator®, to decontaminate a firetruck at Tyndall Airforce Base. During the successful project, Enspired performed simultaneous PFAS removal and destruction, maximized PFAS desorption from equipment interior surfaces, minimized waste volume, and met client effluent regulatory limits and time constraints.

 
Study Highlights   
  • Successful combination of effective cleanout of the PFAS-impacted firefighting system and efficient destruction of the PFAS residuals in the rinsate;
  •  Decontamination and destruction process completed in less than 48 hours;
  •  16.8 grams PFAS removed and destroyed in PFASigator-firetruck recirculation loop for AFFF Foam Tanks and associated pipes, 20 times greater than the 0.8 grams PFAS removed by a single-rinse;
  •  Only 120 gallons of water was used for the cleanout of the Oshkosh TA-1500 firetruck;
  •  EPA PFAS MCLs were met after polishing steps and no other products of concern were generated from the PRD process;
  •  Rebound of total PFAS (including TOP assay analysis of unidentified PFCA precursors) was at low ppb levels 12 days after refilling the decontaminated AFFF foam tank with clean water.

Pilot Project Objectives

The transition from aqueous film-forming foam (AFFF) to fluorine-free foams (F3) and the associated progressive regulatory measures such as the 2023 National Defense Authorization Act to phase out purchase and usage of PFAS-containing AFFF enforce a need to decontaminate the interior surfaces of the PFAS-impacted firefighting systems. Unfortunately, current cleanup methods focus heavily on cleanout, leaving large volumes of PFAS-contaminated rinsate water unaddressed. Also, PFAS stuck to interior surfaces is resistant to removal. As a result, even after many time consuming sequential rinses, PFAS on interior surfaces serve as long-lasting PFAS source, leading to PFAS rebound in the solution that the fire system is ultimately refilled with.

This field demonstration used PFASigator equipment to implement photo-activated reductive defluorination (PRD) to make several advances in firetruck decontamination techniques: (1) simultaneously releasing PFAS from the system interior surfaces and destroying the molecules in solution; (2) augmenting PFAS desorption from interior surfaces with surfactant addition, temperature increase (40 – 50°C), and constant PFAS destruction in aqueous phase; and (3) minimizing water usage and eliminating the need for off-site PFAS disposal.

A truck parked next to a person

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Pilot Project Design

PFASigator implements Enspired Solutions’ patented PRD reactions to breakdown PFAS molecules into non-toxic byproducts under atmospheric temperature and pressure. Designed as modular equipment with a small footprint and fully automatic control, PFASigator is easily mobilized and fits into various application scenarios. The ease of PFASigator implementation enables direct connection with a fire truck for recirculating solution between the two systems to breakdown PFAS molecules while facilitating desorption of PFAS from firefighting truck (Figure 2).

The firetruck for this demonstration was an Oshkosh TA-1500 (Year 1993 model, 31’ long, 12’ tall, 10’ height) that had decades of service history. The truck contained two AFFF sub-tanks, both of which were coated with fiberglass internally, a material with strong PFAS adsorption. PFASigator was connected directly with each foam tank and the associated piping to form a recirculation loop. Approximately 120 gallons of water was recirculated between one AFFF tank and the PFASigator at 25 gallons per minute (gpm), with a temperature raised to 40-50°C when the PRD reaction was initialized. Fluoride production was measured in real-time by the PFASigator automated fluoride ion-selective electrode (ISE) as the direct indicator of PFAS destruction progress. Water samples were collected from the recirculation loop and sent to an analytical laboratory for PFAS, unidentified precursors, fluoride, potential byproducts, and other wet chemistry analyses. The test was conducted for the primary foam tank and the associated piping and then repeated for the secondary foam tank and the associated piping. Upon the completion of PFAS destruction phase, the treated recirculation rinsate was polished via a small vessel containing reversible sorbent media. The trace PFAS sorbed by this media can be washed-off and further destructed by PFASigator.

Demonstration Results and Conclusions

(A) Removed and destroyed 20 times more PFAS in less than 48 hours compared to single water rinse.

Tap water was recirculated at 25 gpm between PFASigator and the firetruck for multiple hours. Table 1 shows the PFAS released from the primary tank in this single water rinse reached a concentration of 1.8 mg/L (ppm), including all 40 PFAS analytes per EPA 1633 list and the unidentified precursors quantified by TOP assay. Adding surfactant to the recirculating water did not significantly impact PFAS desorption. However, initialization of PRD reaction resulted in real-time measurement of fluoride continuously increasing, well beyond the equivalent destruction of 1.8 mg PFAS/L, until a plateau was reached within48 hours (Figure 1). Fluoride measurements were confirmed by analysis with EPA method 300.0 (ion chromatography) at a third-party laboratory. The 24.2 mg/L fluoride production quantified by EPA method 300.0, represented that a total of 16.8 g PFAS was removed and destroyed in PFASigator-firetruck recirculation loop with the AFFF tank and associated piping. This is 20 times greater than the 0.8 g PFAS removed from the single rinse. Similar results were produced for the AFFF secondary tank within 24 hours. During the destruction phase, PFAS destruction and desorption occurred simultaneously. A combination of co-occurring PFAS destruction, recirculation and elevated water temperature (40 – 50°C) contributed to continuous PFAS removal.

(B) Limited amount of water was used for firetruck decontamination with no off-site disposal.

Once connecting PFASigator and firetruck in a recirculation loop, PFAS destruction and desorption occurred simultaneously. This setup combined PFAS removal and destruction in one single step, using water equivalent to volume needed to fill the system only once (~120 gallons), and was able to wash off and destruct 20 times of PFAS from the interior surface of the foam tank and piping than water wash only. Also, the recirculation loop was conducted in neutral pH, atmospheric pressure, at a temperature not higher than 50°C, which posed no concerns or any harmful damages on the system interiors.

(C) EPA PFAS MCLs were met after rinsate polish. No other products of concern were generated from the PRD process.

Upon completion of the PFAS destruction phase, the treated recirculation solution was polished via a small vessel containing reversible sorbent media to remove the trace PFAS remaining in the water. As shown in Table 1, all PFAS with EPA MCLs were non-detect at <2.1 ppt in the filtered water, providing a high level of flexibility and wide options for the final water disposal. The trace PFAS that had been sorbed can be washed-off from the media once the vessel is saturated, which can be further destroyed by PFASigator. Additionally, the treated recirculation rinsate was analyzed for metals, TOC, and several potential byproducts. The results demonstrated that no other products of concern were generated from the PRD process.

(D) PFAS rebound after 12 days was at low ppb levels.

After decontamination of the AFFF tank and associated piping was completed, the tank was refilled with clean tap water. A sample was collected after 12 days after the refill and the results are shown in both Table 1 and Figure 4. The concentration of the total 40 PFAS compounds in the rebound sample was 56 ppb while the unidentified precursors was 80 ppb. The overall PFAS concentrations of the rebound sample were significantly lower (93%) than the water sample collected from the initial tank fill (single water rinsate).

Overall, this demonstration is a revolutionary setup for decontamination PFAS-impacted firefighting systems. PFAS cleanout and destruction were combined to occur simultaneously, maximizing PFAS desorption from system interior surfaces, minimizing waste volume and meeting clients’ regulatory discharge limits and time constraints.

Acknowledgements

Thank you to our project partners: Department of Defense, Environmental Security Technology Certification Program, Tyndall Airforce Base Silver Flag Team, and our great Enspired team for their support throughout the demonstration and especially for safely operating through Hurricane Milton and Hurricane Helene with PFASigator during the 2024 summer.