Electrolytic circulation well coupled with oxidation and reduction for trichloroethylene degradation in groundwater

Trichloroethylene (TCE) is a common organic pollutant in groundwater. Traditional groundwater circulation wells (GCW) are effective but time -consuming and requires ground treatment. This study develops a coupled system for treating TCE -contaminated groundwater through sequential chemical oxidation and reduction. In this system, groundwater is circulated by two separated wells, and electrolysis in a pumping well is utilized to generate O2 and H2 in situ. To degrade TCE, Fe（Ⅱ） -EDTA is added to activate O2 to hydroxyl radicals for oxidation, and Pd catalyst is coupled to catalyze H2 for reduction. The system performance is evaluated in a 2D sandy tank. The initial TCE concentration in the tank is 7.50 mg/L. After 13 days of continuous electrolytic treatment, TCE concentration decreases to 1.65 mg/L (78%). The corresponding increase in Cl-concentration (118.20 μmol/L) is nearly three times that of the decrease in TCE concentration (44.50 μmol/L), which proves the near complete TCE dichlorination. During the operation, the average degradation rate of TCE decreases from 0.90 (0~5 d) to 0.10 (9~13 d) mg/(L·d). Oxidative degradation mainly occurres in the early stage, and catalytic reduction efficiency is relatively stable. The degradation efficiency of both mechanisms decreased gradually in the later stage, which is attributed to the decreased concentration of dissolved Fe（Ⅱ） and decreased activity of Pd catalyst. The coupled system is an improvement of GCW technique, which is feasible for oxidizing and reducing a wide range of different organic contaminants.