This study is aimed at developing a novel treatment train that combines electrocoagulation (EC) with electrochemical oxidation (EO) treatment to remove and degrade perfluoroalkyl acids (PFAAs) and their organic co-contaminants in contaminated groundwater. PFAAs are extremely persistent because of their unique molecular structures, and currently, there is no cost-effective technology that is applicable for on-site PFAA destruction. This study is of great societal and environmental significance by providing a technology potentially practical for eliminating and destructing PFAAs in groundwater. Although PFAAs are proposed to be tested as the target contaminants in this study, the EC and EO technologies can be used individually or in combination to address a wide range of different co-contaminants.

Building upon the team’s past laboratory data, the researchers hypothesize that a treatment train coupling EC and EO can effectively address PFAAs and co-contaminants in groundwater. PFAAs and co-contaminants will be sorbed and concentrated on the flocs formed through EC. The flocs will then be dissolved in a low volume of acidic solution releasing PFAAs into the same acidic solution. PFAAs will then be destroyed effectively with the EO process. Specifically, the PFAAs and co-contaminants can be concentrated by a cost-effective EC process and then destructed by an efficient EO process. The study will be performed in four tasks. Task 1 is a laboratory bench study to verify and optimize the performance of EC and separation of PFAAs and co-contaminants from flocs. The study will first use deionized water spiked with the target PFAAs and co-contaminants, and then groundwater samples collected from Department of Defense (DoD) sites. Task 2 is a laboratory bench study to combine the individual treatment processes in an integral train and evaluate its performance. The EC treatment conditions will be selected based on the Task 1 results. EO treatment conditions will be selected based on the data collected from other studies. Both spiked water system and DoD site groundwater will be used in the treatment train study. Operation and treatment performance data will be collected from each process to evaluate its individual performance and as a whole. Task 3 is a pilot study to simulate the sequential and flow-through treatment train receiving the extracted groundwater from a DoD site. Researchers are aware of several potential sites where the project would be applicable, and will work with the DoD to identify the best candidate site for this project. Researchers will use Wurtsmith Air Force Base (WAFB) in Oscoda, Michigan, where a full-scale granular activated carbon (GAC) treatment system was built for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) treatment with an operation issue of frequent GAC change-outs. Task 4 will include project management; reporting, preparation of multiple peer-reviewed technical journal manuscripts, technology transfer, and an evaluation of life-cycle cost benefit for technology commercialization.

This research will support SERDP’s mission to reduce the DoD’s liabilities by developing sustainable, cost-effective technologies for expedited site cleanup and closure by proposing a treatment train that can remove and degrade PFAAs and co-contaminants in groundwater. This coupling approach allows for the treatment of contaminant concentrations from parts per trillion (ppt) to parts per million (ppm) levels and requires low energy consumption with no sorbent regeneration and PFAA waste generation. The project will prove the treatment effectiveness of the individual processes and the coupled processes. It is also important to note that the treatment train involves EO destruction on site, therefore it avoids off-site treatment (i.e., incineration). (Anticipated Project Completion - 01/2021)

Shi, H., S.Y.D. Chiang, Y. Wang, Y. Wang, S. Liang, J. Zhou, R. Fontanez, S. Gao, and Q. Huang. 2021. An Electrocoagulation and Electrooxidation Treatment Train to Remove and Degrade Per-and Polyfluoroalkyl Substances in Aqueous Solution. Science of The Total Environment, 788:147723.