Aqueous film-foaming foams were widely used for firefighter training exercises and fire response. Due to their stability at high temperature and amphiphilic properties, these foams contain per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Additionally, chlorinated solvents, such as tetrachloroethene (PCE) and trichloroethene (TCE), were commonly used for aircraft engine cleaning, paint removal, and degreasing metal parts. Thus, impacted groundwater plumes often contain mixtures of chlorinated solvents and PFAS, both of which have stringent drinking water standards. Although bioremediation is commonly used to treat PCE and TCE, most PFAS are extremely recalcitrant to conventional thermal, chemical, or biological treatments. The goals of this project were to develop coupled in situ remediation approaches that could be used to effectively treat groundwater plumes containing mixtures of PFAS and chlorinated ethenes, and to understand the potential synergies and limitations of these combined remedies.

This project was structured around three integrated tasks that were designed to (1) develop and test highly reactive materials capable of degrading and/or sequestering PFAS and chlorinated ethenes, (2) develop biological systems to treat chlorinated ethenes and PFAS reaction byproducts following sorptive and reactive treatment, and (3) evaluate the performance of the combined physicochemical and biological systems developed in Tasks 1 and 2 using groundwater containing mixtures of PFAS and chlorinated ethenes. The first system consisted of an upgradient microbial reductive dichlorination zone to treat PCE and TCE, followed in series by a sorptive barrier to remove and sequester PFAS and any other byproducts. The second system consisted of a reactive barrier to degrade PFAS and chlorinated ethenes, coupled with a downgradient sorptive barrier to capture residual reaction byproducts. Materials used in the permeable barriers can be delivered as an aqueous suspension, emplaced as a trench, or as a “funnel and gate” system.

Microcosm studies, conducted with a mixture of 10 PFAS at concentrations of up to 120 mg/L, indicated that the time required for microbial reductive dechlorination of PCE and TCE was not impaired in the presence of PFAS. In addition, growth of Dehalococcoides mccartyi (Dhc) strains responsible for ethene formation were not impacted by PFAS, but at the highest PFAS concentration tested, Dhc shifted from cells harboring the vcrA gene to cells harboring the bvcA gene. The project team synthesized iron oxide nanocapsules coated with polyethylenimine, which exhibited large adsorption capacities for both PFOA and PFOS. Composite materials were also synthesized from metal organic frameworks with titanium dioxide nanoparticles to degrade PFOA under ultraviolet irradiation, and an electrochemical-based (cathodic) process was demonstrated for rapid PFOS degradation. Finally, injectable stabilized ion excahnge resin and powdered activated carbon were developed for permeable adsorptive barriers that could be implemented individually or combined in series to treat groundwater plumes containing mixtures of chlorinated ethenes and PFAS.  

The overall goal of this project was to develop coupled biological and physical-chemical systems that can be used to treat groundwater plumes containing mixtures of chlorinated ethenes and PFAS. The project team was able to synthesize iron oxide nanoparticles coated with polyethyleneimine that exhibited large adsorption capacities for both PFOA and PFOS. The findings of this project were distributed to remediation professionals, site managers, and academic researchers via publications, web-based media, seminars, and active participation of the research team in organizations such as the Interstate Technology and Regulatory Council. Two of the injectable adsorptive materials developed as part of this project will be evaluated in the field as part of ESTCP demonstration project ER23-7936. This research yielded data essential for the development of advanced technologies aimed at enhancing ongoing remediation efforts at PFAS-impacted sites, thereby providing crucial safeguards for warfighters and installation communities. (Project Completion - 2024)

Hnatko, J.P., C. Liu, J. Elsey, S. Dong, J.D. Fortner, K.D. Pennell, L.M. Abriola and N.L. Cápiro. 2023. Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium is not Inhibited by Perfluoroalkyl Acids (PFAAs) at Field-Relevant Concentrations. Environmental Science and Technology, 57:8301-8312. doi.org/10.1021/acs.est.2c04815

Lee, J., C. Kim, C. Liu, M. Wong, N.L. Cápiro, K.D. Pennell, and J.D. Fortner. 2023. Ultra-high Capacity, Multifunctional Nanoscale Sorbents for PFOA and PFOS Treatment. NPJ Clean Water, 6:62. doi.org/10.1038/s41545-023-00263-9

Liao, S., M. Arshadi, M.J. Woodcock, Z.S.S.L. Saleeba, D. Pinchbeck, C. Liu, N.L. Cápiro, L.M. Abriola, K.D. Pennell. 2022. Influence of Residual Nonaqueous-Phase Liquids (NAPLs) on the Transport and Retention of Perfluoroalkyl Substances. Environmental Science and Technology, 56(12):7976–7985. doi.org/10.1021/acs.est.2c00858.

Liao, S., Z. Saleeba, J.D. Bryant, L.M. Abriola, K.D. Pennell. 2021. Influence of Aqueous Film Forming Foams on the Solubility and Mobilization of Non-Aqueous Phase Liquid Contaminants in Quartz Sands. Water Research, 195:116975. doi.org/10.1016/j.watres.2021.116975.

Liu, C., J. Chu, N.L. Cápiro, J.D. Fortner, and K.D. Pennell. 2022. In Situ Sequestration of Perfluoroalkyl Substances Using Polymer-Stabilized Ion Exchange Resin. Journal of Hazardous Materials, 422:126960. doi.org/10.1016/j.jhazmat.2021.126960. 

Liu, C., J. Hatton, W.A. Arnold, M.F. Simcik, and K.D. Pennell. 2020. In Situ Sequestration of Per- and Polyfluoroalkyl Substances (PFAS) Using Polymer-Stabilized Powdered Activated Carbon. Environmental Science and Technology, 54:6929–6936. doi.org/10.1021/acs.est.0c00155.

Naidu, R., P. Nadebaum, C. Fang, I.T. Cousins, K. Pennell, J. Conder, C.J. Newell, D. Longpré, S. Warner, N.D. Crosbie, A. Surapaneni, D. Bekele, R. Spiese, T. Bradshaw, D. Slee, Y. Liu, F. Qi, M. Mallavarapu, L. Duan, L. McLeod, M. Bowman, B. Richmond, P. Srivastava, S. Chadalavada, A. Umeh, B. Biswas, A. Barclay, J. Simon, and P. Nathanial. 2020. Per- and Polyfluoroalkyl Substances (PFAS) Current Status and Research Needs. Environmental Technology and Innovation, 19:100915. doi.org/10.1016/j.eti.2020.100915.

Dissertation

Lui, C. 2021. In Situ Sequestration of Perfluoroalkyl Substances Using Polymer-Stabilized Adsorbents (Ph.D. Dissertation). Brown University.