Electrochemical treatment is a promising emerging technology in which direct current is applied to drive the degradation of aqueous contaminants. Several bench‐scale studies have demonstrated the capability of electrochemical oxidation to fully mineralize refractory organics such as pesticides and perfluorinated compounds. However, insights into large‐scale design and field performance are critically lacking. Here, we designed six pilot‐scale reactors and tested their performance and efficiency for the treatment of groundwater contaminated with 1,4‐dioxane (1,4‐DX) at concentrations exceeding 1000 mg/L. Anode surface area‐normalized degradation rates increased with increasing potential applied, while the process was more energy‐efficient per mass unit removed at low potentials. While not all 1,4‐DX was completely mineralized, the detected ring‐opening intermediates are known to be readily biodegradable. Analyses of potential by‐products from chloride oxidation revealed the generation of chloromethanes and perchlorate at low mg/L concentrations. Towards the end of the 8.5‐month pilot test, decreasing currents and degradation rates indicated progressing passivation of the electrodes, likely due to cathodic carbonate precipitation and/or poisoning by the uniquely high organic carbon load of this source zone groundwater. The findings of our study demonstrate that electrochemical groundwater remediation is a capable approach for the treatment of persistent organic pollutants. Our pilot‐scale test provides practitioners with a basis for evaluating its efficiency under site‐specific conditions and collecting critical performance metrics for technology scale‐up.

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