Case Studies

Pilot Demonstration of PFASigator™ PFAS Destruction in Groundwater Concentrate

In November 2023, Enspired Solutions conducted a pilot demonstration of our groundbreaking PFAS destruction technology, the PFASigator™. During the successful project, we were able to efficiently destroy PFAS in groundwater concentrate at an industrial site, meet client effluent regulatory limits, and achieve zero off-site PFAS disposal.

Study Highlights

  • Successfully treated PFAS-contaminated groundwater with ~1,500 ppt PFOS and a flow rate of 5 GPM on site for one month resulting in zero off-site PFAS disposal
  • Using foam fractionation, transformed high-volume, low-PFAS groundwater into low-volume, high-PFAS, destruction-ready concentrate
  • Using PFASigator, efficiently destroyed PFAS in groundwater concentrate
  • Confirmed PFAS destruction in real time using fluoride-ion monitoring
  • Achieved site-specific discharge limit of < 28 ppt PFOS for duration of the pilot


Pilot Project Objectives

Project objectives were to demonstrate Enspired Solutions’ ability to destroy PFAS in contaminated groundwater at the commercial scale, eliminate the need for off-site PFAS disposal, and meet site-specific discharge PFAS criteria using photo-activated reductive defluorination (PRD) and the PFASigator. The project also demonstrated the ability to combine PRD with foam fractionation (FF) to optimize PFAS destruction efficiency.

The PFAS-contaminated groundwater selected for the pilot test was pumped from a well at an industrial facility at 5 GPM. Analytical testing of the groundwater prior to treatment showed PFOS at levels exceeding 1,500 ppt. The site discharge limit for PFOS is < 28 ppt.

Pilot Project Design

PFAS contaminated groundwater (System Influent) was pumped into tanks for subsequent treatment. The tanks were connected to a recirculating PFAS treatment loop that began with a FF unit where air and boost reagent were added to separate and concentrate PFAS from the System Influent and generate a destruction-ready, low-volume foam with high PFAS concentration. The foam concentrate was then conveyed to the PFASigator in batches where reagents were added to prepare for PFAS destruction using PRD. Each foam concentrate batch was then circulated through the PFASigator’s ultraviolet light reactor to catalyze the PRD reaction. When real-time monitoring of fluoride ions released during PFAS destruction indicated batch treatment was complete, PFASigator effluent was recycled back to the FF unit. Foam production in the FF unit was controlled such that discharge from the FF unit (System Effluent) met the site-specific discharge requirements. The pilot-scale treatment plant at the site is shown in Figure 1.


Figure 1 —Pilot-scale treatment plant including totes of contaminated groundwater (left), the foam fractionation unit (center back, provided and operated by ECT2) and PFASigator (right).

Pilot Project Results and Conclusions

  1. Transformed high-volume, low-PFAS groundwater into destruction-ready concentrate
    Approximately 50,000 gallons of groundwater were treated during the pilot project. The FF unit successfully separated and concentrated PFAS from the source groundwater and produced destruction-ready foam concentrate. During FF, the PFOS concentration increased from approximately 1,500 ppt in the source groundwater (System Influent) to 600,000 ppt in the foam concentrate that was delivered to the PFASigator.
  2. Efficiently destroyed PFAS on site
    PFAS destruction efficiencies using PFASigator were excellent. After a startup period during  which operational conditions were optimized for both the FF unit and PFASigator, destruction extents for PFOS in test batches ranged from 87.2% to 99.7%. PFASigator performance results for both PFOS and total PFAS are illustrated in Figure 2.



Figure 2 — PFOS (top) and total PFAS (bottom) concentrations in foam batches pre and post treatment in the PFASigator and percent destruction for each batch.

  1. Recirculating process flow achieved discharge limit and zero off-site PFAS disposal 
    PFASigator effluent was recycled back to the FF unit at the start of the recirculating PFAS treatment loop. By blending PFASigator discharge with the source groundwater (System Influent), steady-state operation was achieved between FF and PFAS destruction while maintaining < 4 ppt PFOS in the full System Effluent. This closed-circuit concentration and destruction loop eliminated the need for off-site PFAS disposal. The recirculating process flow and performance metrics for a representative test batch can be seen in Figure 3.


Figure 3 — Recirculating process flow and test batch performance metrics for PFAS treatment using FF for PFAS separation and concentration and the PFASigator for PFAS destruction.

  1. Real-time fluoride monitoring confirms PFAS destruction
    As PFAS destruction occurs and carbon-fluorine bonds are broken in PRD, fluorine is released into solution as inorganic fluoride ions. The PFASigator is equipped with a real-time fluoride ion-selective electrode (ISE) probe. Figure 4 illustrates real-time fluoride monitoring data and the resulting fluorine/fluoride mass balance. From start to end of the PFAS destruction batch, over 96% of the decrease in organic fluorine is accounted for by the observed increase in fluoride ions. The excellent fluorine mass balance achieved using PRD indicates 1) the utility of using fluoride ion as a proxy for extent of PFAS destruction and 2) the PRD reaction defluorinates PFAS with little loss of PFAS to other pathways such as physical adsorption, conversion into toxic byproducts, etc.


Figure 4 — Fluorine/fluoride mass balance overlapped with real-time fluoride monitoring for one PFAS destruction batch. Fluorine masses were calculated for the sum of organic fluorine concentration in each PFAS analyte, grouped into categories shown in colorful bars. The final measured fluoride concentration represents 96% of the decrease in organic fluorine mass between batch start and batch end.

Overall, results of this study demonstrate the ability to destroy PFAS in contaminated groundwater at commercial scale using the PFASigator, eliminate the need for off-site PFAS disposal, and meet site-specific PFAS discharge criteria. The project also demonstrated the ability to combine PFASigator with FF to optimize PFAS destruction efficiency.

Acknowledgements

Thank you to our project partners: the owner and operators of the industrial facility at which this project was executed; Emerging Compounds Treatment Technologies (ECT2); and United States Bureau of Reclamation, Desalination and Water Purification Research Program.