The purpose of this pilot-scale investigation was to validate the effectiveness and develop scale-up criteria for integrating a per- and polyfluoroalkyl substance (PFAS) treatment and destruction technology into existing groundwater treatment systems. This pilot study evaluated the effectiveness of the PFAS treatment train: ion exchange resin, resin regeneration, distillation of spent regenerant, and low energy plasma destruction of concentrated PFAS waste.
The goal of this project was to demonstrate the effectiveness of the proposed PFAS treatment train and provide guidance on how to integrate the treatment train into existing co-occurring chemical treatment systems. Specific technical objectives included:
The pilot-scale PFAS treatment train consisted of four technologies that complemented each other to remove PFAS from treated water with reusable media, reduce the volume of the PFAS-impacted waste stream, and destroy that waste stream on-site:
The first performance objective for the pilot test was to demonstrate that the HC1 IX resin was able to consistently treat the incoming groundwater to levels at or below the EPA Lifetime Health Advisory (2016). The sum of analyzed PFAS remained at greater than 95% removal efficiency. The second performance objective for the pilot test was to demonstrate the successful reuse of regenerated IX resin over multiple loading cycles and recovery of the regenerant solution using distillation. The original HC1 resin loaded at the start of the pilot test remained in use for the duration of the test and continued to provide PFAS treatment effectively, meeting PFAS removal performance objectives. The performance objective for plasma destruction of the still bottoms was that all identified PFAS be below 70 ppt on an individual compound’s basis. All measured PFAS were below detection limits at the conclusion of treatment, exceeding the performance objective, except for PFBA.
The need for pre-treatment of influent water was understood at the outset of this pilot study as a requirement to effectively operate the system. As influent water quality and co-occurring chemicals will vary for each site, an appropriate pre-treatment design, bench testing, and operational optimization may be required. This PFAS Treatment Train can be integrated into existing groundwater treatment systems with co-occurring chemicals, typically after the existing treatment processes, as long as there is appropriate pre-treatment of the influent water prior to the PFAS Treatment Train.
The findings from the pilot study have been used to develop a cost model for regenerable IX/distillation/plasma scenario to be used as a comparison to other currently available technologies. While each of the PFAS treatment technologies has its advantages and disadvantages, and while it remains true that site specific conditions will generally determine which treatment alternative is selected, some key takeaways from this project can be made that will help in the decision framework:
In general, this technology appears to have good performance and can be cost competitive with other currently available technologies depending on individual site-specific requirements.
The following issues are presented to help with additional design considerations:
(Project Completion - 2023)
Blossom N.N., M. Crimi, S. Mededovic Thagard, and T.M. Holsen. 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS). Critical Reviews in Environmental Science and Technology, 49(10):866-915. doi.org/10.1080/10643389.2018.1542916.
Kempisty, D.M., Y. Xing, and L. Racz. 2018. Chapter 14: Ion Exchange for PFAS Removal. In Perfluoroalkyl Substances in the Environment: Theory, Practice, and Innovation (Environmental and Occupational Health Series), 1st edition S. Woodard (Ed.), CRC Press, 325-352.
Kempisty, D.M., Y. Xing, and L. Racz. 2018. Chapter 21: Case Study: Pilot Testing Synthetic Media and Granular Activated Carbon for Treatment of Poly- and Perfluorinated Alkyl Substances in Groundwater. In Perfluoroalkyl Substances in the Environment: Theory, Practice, and Innovation (Environmental and Occupational Health Series), 1st edition; S. Woodard (Ed.), CRC Press, 467–484.
Shangtao, L., R. Mora, Q. Huang, R. Casson, Y. Wang, S. Woodard, and H. Anderson. 2022. Field Demonstration of Coupling Ion-Exchange Resin with Electrochemical Oxidation for Enhanced Treatment of Per- and Polyfluoroalkyl Substances (PFAS) in Groundwater. Chemical Engineering Journal Advances, 9:100216. doi.org/10.1016/j.ceja.2021.100216.
Singh, R.K., S. Fernando, S.F. Baygi, N. Multari, S. Mededovic Thagard, and T.M. Holsen. 2019. Breakdown Products from Perfluorinated Alkyl Substances (PFAS) Degradation in a Plasma-Based Water Treatment Process. Environmental Science and Technology, 53(5):2731–2738. doi.org/10.1021/acs.est.8b07031.
Singh, R.K., N. Multari, C. Nau-Hix, R.H. Anderson, S.D. Richardson, T.M. Holsen, and S. Mededovic Thagard. 2019. Rapid Removal of Poly- and Perﬂuorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor. Environmental Science and Technology, 53(19):11375-11382. doi.org/10.1021/acs.est.9b02964.
Singh, R.J., N. Multari, C. Nau-Hix, S. Woodard, M. Nickelsen, S. Mededovic Thagard, and T.M. Holsen. 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21):13973−13980. doi.org/10.1021/acs.est.0c02158.
Wang, L., M. Nickelsen, S.Y. Chiang, S. Woodard, Y. Wang, S. Liang, R. Mora, R. Fontanez, H. Anderson, and Q. Huang. 2021. Treatment of Perfluoroalkyl Acids in Concentrated Wastes from Regeneration of Spent Ion Exchange Resin by Electrochemical Exidation using Magnéli Phase Ti4O7 Anode. Chemical Engineering Journal Advances, 5:100078. doi.org/10.1016/j.ceja.2020.100078.