Superfund Research Program

Portable, Self-Cleaning Advanced Electro-Oxidation Systems for Distributed and Point-of-Use Water Treatment

Project Leader: Akram N. Alshawabkeh
Co-Investigators: April Z. Gu (Cornell University), Philip Larese-Casanova
Grant Number: P42ES017198
Funding Period: 2010-2025

Project-Specific Links

Final Progress Reports

Year:   2019  2013 

Studies and Results

The goal of this project is to develop novel, sustainable, solar-powered and environmentally-friendly technology for remediation of contaminated groundwater, especially in karst regions. Dr. Alshawabkeh and his team of investigators will use solar panels to apply low direct electric currents through electrodes in wells to manipulate groundwater chemistry by electrolysis. Their target contaminants are chlorinated solvents, specifically trichloroethylene (TCE), but the process will also be designed to treat a mixture of contaminants. Two specific transformation mechanisms are evaluated: electrochemical reduction and chemical oxidation. Previously the investigators measured the geochemical changes induced by the process and demonstrated that chemically reducing groundwater could be developed by iron anodes, leading to almost complete dechlorination of aqueous TCE. They also evaluated chemical oxidation of TCE in groundwater by electro-generated reactive oxygen species. They identified conditions (e.g., current rates and geochemistry) for optimum transformation and demonstrated the potential of electrochemically induced transformation of other chemicals.

The team investigated the effects of chemicals, specifically reduced sulfur compounds (RSCs), on Pd-catalytic hydrodechlorination of TCE. This is important since the catalytic activity of Pd significantly decreases in the presence of reduced sulfur compounds (RSCs), such as sulfite and sulfide, generated from sulfate-reducing bacteria respiration. They discovered a distinct mechanism for the effect of sulfite on TCE hydrodechlorination by Pd and H2 in oxic groundwater and published the results (in ES&T) with an alternative approach to increasing resistance of Pd to RSCs poisoning. Currently the investigators are building a pilot-scale laboratory system that includes a pump and a treatment unit; both operated by a solar panel. The system will be tested in the lab to assess performance and identify potential challenges. In collaboration with Prof. April Gu, Giese (Discovery of Xenobiotics Associated with Preterm Birth project) and Loch-Caruso (Pollutant Activation of Cell Pathways in Gestational Tissues project) Dr. Alshawabkeh and his team of investigators are assessing toxicity evolution by the electrochemical oxidation process using a new innovative toxicogenomics-based toxicity assessment method. The evolution of toxicity, particularly the detailed mode of action, during the course of degradation was evaluated. The results show that while concentration of some chemicals (e.g. Ibuprofen) decreases by the process, the overall toxicity of the intermediates increased shortly after treatment before it finally decreased. This indicates that decrease in contaminant concentration is not sufficient and longer treatment may be necessary. In addition, the detailed stress response pathway information showed that the potential toxicity action mode and profile, expressed in redox, protein, membrane and DNA stress index value (TELI) etc., were quite distinct over time. Correlation of the toxicity evolution information with identified intermediates led to the insights of a possible transformation pathway and potential toxicity mechanism associated with different intermediates. These results are summarized in a recent publication in Chemosphere.

The investigators compared the performance and environmental impacts of the technology as an Electrochemical E-Barrier with conventional permeable reactive barriers (PRB's). They used a theoretical case study for the E-barrier system to quantitatively establish the technology as environmentally friendly. Based on data availability they identified a pilot-scale and full-scale developed by Battelle for the Dover Air Force Base (AFB) contaminated VOC's plume in Dover, DE, an analysis was made to obtain major design elements, materials, and energy usage. The team conducted an LCA analysis and identified the major drivers of impacts in both technologies. Sensitivity analysis was conducted in order to determine the robustness of the models.

Significance

The project is focused on green and sustainable treatment of chlorinated solvents, including TCE, which are among the most frequently encountered and persistent contaminants in soil and groundwater in the United States. This project is also significant for improving the state-of-knowledge on electrochemical transformation of chemicals in water.