Remediation of COD-Contaminated Groundwater by Coupled Electro-Fenton and Groundwater Circulation Well: An Experimental Study.

Groundwater circulation well (GCW) technology and electro-Fenton (EF) technology offer promising prospects for groundwater remediation due to their high efficiency in removing volatile organic compounds and their advantage of causing no secondary pollution. In this study, chemical oxygen demand (COD) was selected as the target contaminant to investigate the remediation performance of the EF coupled with GCW technology. The results indicate that the optimal COD removal was achieved at an applied voltage of 30 V, as higher voltages facilitate the accelerated generation of ·OH radicals, thereby enhancing the degradation rate of pollutants. However, excessively high voltages may lead to increased current, elevated energy consumption, and potential anode damage; thus, considering both treatment efficiency and economic cost, 20 V was identified as the optimal voltage. In the coupled EF-GCW system, the optimal aeration rate was determined to be 1.3 L/min. Increasing the aeration rate beyond this value did not significantly improve the removal performance and instead reduced EF efficiency due to decreased dissolved oxygen residence time. Furthermore, the current GCW hydraulic design presents flow blind zones, which limit remediation efficiency in certain regions. This study defines the optimal operational window for the EF-GCW system and provides insights into overcoming hydraulic circulation blind spots, offering valuable process parameters for the optimization and practical application of groundwater remediation technologies.