Grantee Research Project Results
Final Report: Electrochemical Pretreatment of PFAS-Contaminated Aqueous Effluents
EPA Contract Number: 68HERC20C0058Title: Electrochemical Pretreatment of PFAS-Contaminated Aqueous Effluents
Investigators: Lee, Katherine
Small Business: Faraday Technology, Inc.
EPA Contact: Richards, April
Phase: II
Project Period: June 1, 2020 through May 31, 2022 (Extended to May 31, 2023)
Project Amount: $300,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2020) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , SBIR - Water and Wastewater
Description:
The electrochemical oxidation (EO) technology developed in this program addresses the need for efficient and cost-effective technologies that destroy per- and polyfluoroalkyl substances (PFAS) in contaminated water. Existing water treatment techniques (e.g., ion-exchange/granular activated carbon, membrane separation, foam fractionation) separate PFAS from contaminated water, generating PFAS-free water and a PFAS-concentrated waste stream that must itself be treated to prevent re-release of PFAS back into the environment. There is an urgent need for the development of efficient, cost-effective, and scalable technologies for destruction of PFAS. However, the high chemical stability of PFAS makes these species impervious to common biological and chemical degradation processes. EO is an emerging PFAS destruction technology that has the unique ability to drive the complete mineralization of PFAS. EO uses an electrical current/voltage applied to an electrode to drive electron transfer reactions that break PFAS down into environmentally benign products (e.g., CO2. F‒).
A growing number of companies are developing EO systems for treatment of PFAS in industrial wastewater, landfill leachate, groundwater, and other solutions. These EO systems are designed to be used either as a stand-alone technology or as part of a treatment train in which an initial separation technology is followed by EO destruction. While significant strides have been made towards the development and deployment of EO systems, system/process improvements that decrease costs and enable treatment of complex water sources are needed to enable widespread commercial uptake of EO PFAS treatment. Traditional EO PFAS treatment use direct current (DC) waveforms in which a constant voltage or applied current is held for the duration of the trial. However, the use of this constant voltage or applied current is well-known to drive side reactions which decrease energy efficiency, increase costs, and can generate toxic by-products.
In this research program, Faraday developed a pulsed-voltage EO process (FARADAYIC® EO) that uses the power of pulse/pulse-reverse waveforms to maximize the rate of PFAS destruction while minimizing energy-intensive side reactions, thereby decreasing treatment costs. The FARADAYIC® EO process developed is designed to augment commercially available reactor systems, enabling them to reach the performance and economic benchmarks necessary for commercial uptake. During the Phase I program, Faraday demonstrated the technical feasibility of this approach using simple electrolyte solutions and un-optimized reactor configurations. The purpose of the Phase II program was to validate the commercial viability of FARADAYIC® EO by demonstrating efficient, rapid destruction of PFAS in commercially-relevant waste streams with industrial reactor systems.
To demonstrate the commercial viability of FARADAYIC® EO, Faraday evaluated the PFAS destruction performance of DC and FARADAYIC® EO using solutions modelled after PFAS-contaminated landfill leachate. For each waveform, LC-MS/MS and fluoride ISE/ion chromatography was used to quantify the amount of PFAS destroyed and fluoride ion generated, respectively. Using this data, the PFAS destruction performance for each waveform was evaluated in terms of the kinetics of and energy requirements for PFAS destruction as well as the fluoride mass balance. As a capstone demonstration, Faraday validated FARADAYIC® EO in real landfill leachate samples procured from a commercial landfill waste treatment facility.
Specific objectives/tasks completed as part of this work included:
(1) Design a Landfill Leachate Model Solution: Faraday worked with collaborators at U.S. Ecology - who own and operate multiple Subtitle C landfill sites permitted to handle hazardous PFAS waste - to design a test solution that modelled landfill leachate solution. This landfill leachate model solution contained a diverse range of species, including the oxidizable inorganic ion chloride, which have the potential to interfere with PFAS destruction. By working with these solutions, Faraday was able to provide clear evidence of the robustness of FARADAYIC® EO in the presence of common interferences.
(2) Benchmark PFAS Destruction Performance of Commercially-Available EO Reactors Using DC Waveforms: Using this landfill leachate model electrolyte, Faraday conducted DC benchmarking studies with two commercially available EO reactor systems. Both systems used the same type of electrode material (boron doped diamond), but varied the electrode shape and geometry. The first reactor design used electrode plates which the PFAS-contaminated solution flowed-by. The second reactor design - developed by project partner CONDIAS - was a CONDIACELL® Cell Model D20 ECWP which uses perforated boron doped diamond electrodes. During operation, the PFAS-contaminated solution flows through the perforated electrodes. This solution flow is designed to promote turbulence and mass transfer at the electrode surface. As discussed below, the CONDIACELL® was found to provide significant processing advantages and was down-selected for future work.
(3) Compare DC and FARADAYIC® EO: Using the landfill leachate model electrolyte and the CONDIACELL®, Faraday conducted a design-of-experiment with different FARADAYIC® EO waveform parameters. The PFAS destruction performance of these FARADAYIC® EO were compared to results from DC benchmarking studies. Results from these trials are discussed under the Summary of Findings sub-section below.
(4) Validate FARADAYIC® EO in Real Landfill Leachate Samples: Samples of landfill leachate were procured from a hazardous landfill waste treatment center. The landfill leachate has been pretreated using foam fractionation, a PFAS separation technology which generates a PFAS-enriched foam.
(5) Technoeconomic Analysis: To compare the economic performance of DC and FARADAYIC® EO, preliminary analysis of capital and operating expenses was conducted using the experimental results from DC and FARADAYIC® EO trials. This analysis compared the economic performance of DC/FARADAYIC® EO treatment as a stand-alone technology and as part of treatment train involving a foam fractionation pre-treatment followed by EO destruction. Foam fractionation has been reported to achieve PFAS enrichment factors on the order of 10‒1,000,000 (depending on the treatment duration and PFAS identity). The ultimate result is a decrease in the volume of PFAS-contaminated solution to be treated by EO and an increase in the PFAS concentration in that solution. Technoeconomic analysis compared the capital and operating expense required for EO treatment of the higher volume/lower PFAS concentration solution that had not been treated via foam fractionation as well as the lower volume/higher PFAS concentration solution after foam fraction.
Summary/Accomplishments (Outputs/Outcomes):
Key Finding 1: DC benchmarking studies which compared the performance of the flow-through CONDIACELL® and commercial flow-by EO reactor demonstrated that the CONDIACELL® provided significant processing advantages. Specifically, these studies found that (under DC conditions) the CONDIACELL® was able to achieve PFAS destruction 3-3.5x faster with 5.5-6.5x less energy than the flow-by reactor.
Key Finding 2: FARADAYIC® EO provided further enhancement to the PFAS destruction performance of the CONDIACELL®. Specific performance enhancements included:
- For a given voltage, the best performing FARADAYIC® EO waveforms achieved up to a 55% increase in the kinetics of PFAS destruction and a 60% decrease in energy requirements relative to DC.
- For longer timescale experiments (where the PFAS concentration was being decreased by > 99.9%), FARADAYIC® EO achieved the same level of PFAS destruction while stabilizing reactor performance. Specifically, during DC EO trials, a large increase in energy requirements was observed at longer timescales as PFAS concentration decreased. FARADAYIC® EO mitigated this undesirable increase in energy requirements.
- Technoeconomic analysis using data from experimental trial found that FARADAYIC® EO could achieve a 2.7-times reduction in operating expenses and 1.5-times reduction in capital experiments relative to DC EO.
Key Finding 3: Coupling DC/FARADAYIC® EO with a foam fractionation pre-concentration step provided significant capital and operating expenses. Specifically, the capital and operating expense for DC/FARADAYIC® EO treatment of the high volume/low PFAS concentration solution prior to foam fractionation was 5,000-times higher than for the low volume/high PFAS concentration solution after foam fractionation.
Key Finding 4: FARADAYIC® EO enabled safe treatment of real landfill leachate samples that had been pre-treated via foam fractionation. During DC EO treatment in these solutions, excessive gas formation resulting from side reactions led to aggressive foaming/frothing of the solution. The ultimate result was obstruction of flow in the reactor and overflow of PFAS-contaminated solution out of the reactor. The safety/treatment challenges presented by this foam formation have been previously reported for foam fractionation-DC EO treatment trains. Because FARADAYIC® EO minimizes the side reactions that lead to gas formation, FARADAYIC® EO mitigated foaming during treatment and enabled safe reactor operation. In work to date, FARADAYIC® EO of these landfill leachate samples has achieved up to 65% PFOS destruction and 30% PFOA. The ability to enable safe operation of foam fractionation-FARADAYIC® EO treatment trains is significant given the substantial decreases in capital and operating expenses that can be achieved with this treatment train approach.
Conclusions:
Results from the Phase II activity validate that FARADAYIC® EO can provide significant operating advantages in commercially-relevant solutions using industrial reactor systems. Key performance enhancements (relative to DC EO) include faster PFAS destruction kinetics, lower energy requirements for PFAS destruction, more stable reactor performance over longer timescales/larger PFAS concentrations, and enabling safe operation of treatment trains such as tandem foam fractionation- FARADAYIC® EO systems.
During this program, Faraday presented this work at a number of conferences and held one-on-one meetings with commercial, academic, and government entities interested in PFAS destruction technology. Insight from these discussions was used to develop our technology transition plan. Faraday does not anticipate being the eventual manufacturer, distributor, or operator of complete EO treatment systems for PFAS destruction. Rather we will align with strategic partners who will manufacture and distribute the technology. As mentioned above, EO is an established method for the destruction of PFAS and multiple companies are pursuing the commercialization of EO systems for PFAS destruction. Faraday anticipates developing a strategic partnership with at least one of these companies as a next step towards commercialization of FARADAYIC® EO. Given the savings in capital and operating expenses expected by coupling FARADAYIC® EO with a pre-concentration technology, a second prong of the commercialization strategy for FARADAYIC® EO is to form strategic alliances with key players in the separation/concentration technology space (e.g., ion-exchange/granular activated carbon, foam fractionation) and demonstrate the compatibility of FARADAYIC® EO with their technology. We anticipate that a competitive advantage of FARADAYIC® EO (relative to DC EO) will be enhanced compatibility with separation/concentration technology. This is consistent with Phase II results which showed that FARADAYIC® EO was critical for enabling safe and effective PFAS destruction in PFAS-concentrated foam fractionate.
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this projectSBIR Phase I:
Electrochemical Pretreatment of PFAS-Contaminated Aqueous Effluents | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.