Project 5: Remediation of Contaminated Groundwater by Solar-Powered Electrolysis

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PROJECT SUMMARY Study Objectives: Our long-term goal is to develop novel, sustainable, solar-powered and environmentally- friendly technologies for remediation of contaminated groundwater, especially in karst regions. We will use solar panels to apply low direct electric currents through electrodes in wells to manipulate groundwater chemistry by electrolysis. Our 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 we demonstrated that chemically reducing groundwater could be developed by iron anodes, leading to almost complete dechlorination of aqueous TCE. We also evaluated chemical oxidation of TCE in groundwater by electro- generated H2 and O2. Our objectives in this competitive renewal study are to understand and improve the process using innovative electrode systems for transformation of mixtures of contaminants under variable flow rates, assess the transformation pathways and their associated effects on groundwater toxicity, and measure the performance of the process in field-scale testing. Study Approach: We will conduct laboratory experiments in vertical column setups made of acrylic and limestone and in electrochemical reactors. We will use the reactors to test innovative three-electrode treatment units to induce reducing or oxidizing conditions and investigate a novel two electrode system with polarity reversal to achieve oxidizing conditions. We will measure degradation and transformation products, as well as toxicity evolution, during the course of the process in batch electrochemical setups. In addition to a commonly used phenotypic in vitro assay, an innovative newly-developed fast and mechanistic toxicogenomics-based temporal gene or protein expression profiling technique will be employed. The variations of toxicity levels and mechanistic profiles during the course of the electrochemically-induced degradation will disclose the potential causal agents and their links to the degradation pathways. For these laboratory tests, groundwater collected from Puerto Rico will be mixed with target contaminants and used for testing. To facilitate translation of the process into field implementation, we will conduct and measure the performance in a small field-scale test using a single well or multiple wells. Treatment units in the wells will be connected to solar panels/controllers and different operation modes will be tested. Observation wells will be used to monitor changes. Expected Results: We will develop a technology for sustainable remediation of contaminated groundwater. We will design electrochemical reactors with innovative electrode systems for contaminant degradation and prove the reduction or elimination of toxicity during and after the treatment. Finally, we will design and measure the performance of the technology in wells in a small-scale field study in aquifers in karst regions.