Case Studies

Benchtop Demonstration of PRD in Municipal Wastewaters

Authors: Dr. Tess Sobolewski and Sarah Meyer

 

Enspired Solutions has conducted benchtop treatment using our novel technology, photoactivated reductive
defluorination (PRD), for PFAS destruction in several wastewater samples. Results from testing two distinct samples are
discussed below: (1) foam fractionate from municipal wastewater, and (2) reverse osmosis (RO) brine from municipal
wastewater.


 

Study Highlights

  • Sample #1 – Foam fractionate from municipal wastewater
    • Near-complete destruction of PFOS: Achieved >99.9% destruction at UV dose 600 kilowatt hours per cubic meter (kWh/m3)
    • Strong destruction of EPA Maximum Contaminant Level-listed (MCL) PFAS and total PFAS: Achieved 98% destruction of EPA MCL PFAS and 95% destruction of total measured PFAS at 2,400 kWh/m³, with PFOA and PFOS reduced below the EPA MCL of 4 nanograms per liter (ng/L)
  • Sample #2 – Reverse Osmosis (RO) brine from municipal wastewater
    • Near-complete destruction of PFOA and PFOS: Achieved 97% destruction at UV dose 600 kWh/m3
    • Strong destruction of EPA MCL and total PFAS: Achieved 98% destruction of EPA MCL PFAS and 95% destruction of total measured PFAS at 2,400 kWh/m3
    • Effective destruction despite more challenging water quality: little to no effect on destruction rate from low to moderate ultra-violet light transmittance (UVT) (17%), 860 parts per million (ppm) total dissolved solids (TDS), and elevated sulfate and chloride.

PRD achieved strong PFAS destruction across both municipal wastewater samples, with >97% removal of PFOA and PFOS at moderate UV doses and further reductions to near or below regulatory limits at higher doses. Depending on client needs, lower UV doses combined with recirculation can provide a more energy-efficient treatment strategy.

Benchtop Destruction Testing - Results
Sample #1 – Foam fractionate from municipal wastewater

Benchtop testing using PRD was conducted on a composite wastewater foamate seeded with cocamidopropyl hydroxysultaine (CAHS) produced by a foam fractionation vendor. The sample exhibited low TDS (230 ppm), a neutral pH of 7.3, and high UV transmittance (75%). All other wet chemistry was assumed to be consistent with the raw wastewater sample pre-foam fractionation. PFOS was identified as a primary contaminant of concern at the wastewater treatment plant, comprising approximately 26% of total PFAS, while 6:2 FTS accounted for about 30% of the PFAS profile. The sum of EPA MCL PFAS (PFNA, PFOA, PFOS, PFHxS, PFBS, and HFPO-DA) decreased by 95% at 600 kWh/m3 (from 4,166 ng/L to 208 ng/L, and by 98% (to 71 ng/L) at 2,400 kWh/m3 (Figure 1). Total measured PFAS decreased by 82% at 600 kWh/m3 (from 13,279 ng/L to 2,401 ng/L), and by 95% (to 607 ng/L) at 2,400 kWh/m3 (Figure 1).

Sample #2– RObrine from municipal wastewater

Benchtop testing using PRD was conducted on an RO brine derived from a wastewater sample, with primary constituents including PFBS (25%) and PFPeA (15%) of the total PFAS profile. The sample exhibited low TDS (860 ppm), a neutral pH of 7.2, and low to moderate UV transmittance (17%). The sample contained elevated concentrations of sulfate (400 mg/L) and chloride (600 mg/L) prior to destruction treatment due to the RO concentration step. In addition, the sample exhibited observable suspended solids indicating as a high total suspended solid (TSS) level. The sample was treated as raw without any pretreatment steps before PRD reaction. At a UV dose of 600 kWh/m³, PFOA and PFOS achieved 97% destruction, while the sum of EPA MCL PFAS decreased by 95%. At a higher UV dose of 2,400 kWh/m³, the total EPA MCL PFAS decreased further to 98% destruction, from an initial concentration of 3,014 ng/L to 49 ng/L posttreatment (Figure 2). Similarly, total measured PFAS decreased by 68% at 600 kWh/m³ and by 85% at 2,400 kWh/m³, corresponding to a reduction from 7,161 ng/L to 1,080 ng/L (Figure 2).

PRD Benchtop Demonstration for Wastewaters - Conclusions


PRD demonstrated strong performance for PFAS destruction across both municipal wastewater samples, achieving nearcomplete removal of key regulated compounds, PFOA and PFOS, at moderate UV doses. In both the foam fractionate and RO brine samples, PFOA and PFOS were reduced by >97% at a UV dose of 600 kWh/m3. At full scale, even lower effective doses may be achievable when PRD is implemented in a recirculating configuration integrated with foam fractionation or RO systems, where repeated passes can improve overall treatment efficiency.

At a higher UV dose of 2400 kWh/m3, PRD was able to reduce PFOA and PFOS to single digit parts per trillion or below MCLs (4 ppt) and achieve >90% destruction of total PFAS. These results highlight the capability of PRD to meet stringent regulatory targets; however, operating conditions should ultimately be selected based on a cost-benefit balance between energy input and treatment goals. In many cases, a lower UV dose combined with recirculation may provide a more energy-efficient alternative to single-pass, high-dose treatment.


Across both samples, PRD performance remained consistent despite differences in water quality, including the presence of CAHS as a foam fractionation booster reagent, variations in TDS, and differences in UV transmittance. While TDS and UVT can give a general sense of matrix complexity and the potential for radical scavenging, they are not definite predictors of performance. For example, effective PFAS destruction was achieved in both a low-TDS, high-UVT foamate and a higher-TDS, lower-UVT RO brine, suggesting that PRD can perform reliably across a wide range of wastewater conditions.


These results reinforce that PRD performance is site-specific and driven more by overall matrix composition than by any single bulk parameter. As a result, basic water quality characterization, screening, and bench-scale treatability testing represent important, low-cost and efficient steps for estimating reaction kinetics and informing full-scale system capacity and design.


From an implementation standpoint, several practical points stand out:

  • PRD pairs well with upstream concentration technologies like foam fractionation and RO, making it a good fit for treating PFAS-enriched side streams.
  • Performance can be reliably predicted and optimized through site-specific treatability testing.


Overall, these results show that PRD is a flexible and effective PFAS destruction technology that can achieve regulatory targets across a range of wastewater matrices, with multiple pathways available to balance performance and cost depending on site needs.