Case Studies

Enspired Solutions Collaboration with Allonnia and SAFF® to Destroy PFAS in Airport Surface Water

Enspired Solutions® and Allonnia recently collaborated on a successful test of our PFAS treatment technologies to capture and destroy PFAS in surface water at a Midwest airport.

Study Highlights

  • Using Surface Active Foam Fractionation® (SAFF®), Allonnia was able to successfully remove PFAS to concentrations below USEPA drinking water Maximum Contaminant Levels (MCLs) after treatment and generate PFAS concentrate for destruction testing.
  • Using photo-activated reductive defluorination (PRD), Enspired Solutions was able to successfully destroy PFAS in concentrate generated by Allonnia’s SAFF.
  • At a low UV dose of 200 kWh/m3, one to two orders of magnitude degradation was observed in the majority of PFAS compounds.  
  • At a UV dose of 600 kWh/m3, all but two measured PFAS concentrations were reduced to single or double-digit ppt levels. At this dose, the majority of PFAS destruction occurred.
  • Results indicate that practical, on-site PFAS destruction using PRD would be successful using a low UV dose that achieves 1-2 orders of magnitude PFAS destruction and a recirculating process flow that returns the remaining PFAS to the SAFF unit for reconcentration. Using this recirculating process flow can keep energy use low and destruction efficiencies high.

Project Objectives

Historic use of aqueous film-forming foam (AFFF) that contained PFAS at airports to train for and fight fires has resulted in PFAS contamination in groundwater and surface water. The airport is interested in effective options to control off-site migration of PFAS-contaminated surface water. Enspired Solutions and Allonnia tested our combined technologies to capture and destroy PFAS in surface water at the airport.

Results

Allonnia tested three initial treatments of the surface water for PFAS removal: a control (no treatment) and two different additives to enhance PFAS removal. The extent of PFAS removal ranged from 31.2% (control) to 61.3%. When using additives, PFAS concentrations were below USEPA drinking water MCLs after treatment.

Enspired Solutions then used the PFAS concentrate generated by Allonnia in the control test to perform destruction testing using PRD treatment over multiple UV doses. PFAS samples were collected for third-party analysis at UV dosages of 0 kWh/m3, 200 kWh/m3, 600 kWh/m3, 2,400 kWh/m3 and 3,000 kWh/m3. Concentrations of PFAS compounds detected in at least one sample are shown at each UV dose in Figure 1.

Table 1 shows detections and degradation percentages for those PFAS detected in at least one sample. Observations of PFAS destruction at each UV dose were:   

200 kWh/m3 Applied Dose – One to two orders-of-magnitude degradation was observed in the majority of PFAS compounds. The sum of the USEPA’s MCL list of six PFAS (PFNA, PFOA, PFOS, PFHxS, PFBS, and HFPO-DA) decreased by 97.0%. The total PFAS decreased by 91.3%.

600 kWh/m3 Applied Dose – All measured PFAS concentrations were reduced to single or double-digit ppt levels except for PFPeA (450 ppt) and PFBA (270 ppt). This result is expected at this stage because these shorter chain compounds were produced as intermediates by the breakdown of long-chain PFAS compounds. The sum of USEPA’s MCL list of 6 PFAS decreased by 99.9%. Total PFAS decreased by 98.5%.

2,400 kWh/m3 Applied Dose – Over 99% degradation was detected in every PFAS compound measured except for PFBA, which had a concentration of 110 ppt. Furthermore, three out of six PFAS on USEPA’s MCL were reduced to non-detects, and the total PFAS concentration was reduced by 99.7%.

3,000 kWh/m3 Applied Dose – There was an apparent slight increase in total PFAS concentration and a decrease in % destruction after this last measurement. The appearance of an increase was due to the lower detection limits achieved by the analytical lab, as total PFAS concentrations also decreased over the sample set, which allowed for the quantification of additional compounds. Even with this change, a total decrease in PFAS of 99.2% from the untreated sample was observed.

It’s worth noting that the majority of PFAS destruction occurred within a UV dose of 600 kWh/m3. All destruction after the 600 kWh/m3 dose is 1.3% of the total PFAS concentration and 2.6% of the EPA’s MCL PFAS. Practical, on-site PFAS destruction using PRD would be recommended using a relatively low UV dose that achieves 1-2 orders of magnitude PFAS destruction and a recirculating process flow (Figure 2) that returns the remaining PFAS to the SAFF unit for reconcentration. Using this recirculating process flow can keep energy use low and destruction efficiencies high.