(602e) The Influence of Suspended Sediment on Electrochemical Remediation of Karst Groundwater

Electrochemical remediation is an innovative, sustainable, and promising approach for treatment of groundwater in complex terrains such as karst. Electroremediation offers high flexibility in generation and control of conditions needed for the contaminants’ transformation to harmless byproducts. However, performance of the treatment can be affected by the presence of suspended sediments, which appear in karst groundwater due to the direct recharge through sink holes and other areas. In this study, we evaluated the impacts of suspended sediments originating from Meff Cave (MC), Drop Lick Cave (DLC), and Crab Tree Spring (CTS) on electrochemical processes supporting the electro-Fenton reaction. We tested the production rates of in situ electro-generated hydrogen peroxide in the absence (control experiment) and presence of 2 g/L of each sediment sample (particles size <2 mm). The tests were conducted in the flow-through electrochemical reactor under current intensity of 90 mA and flow rate of 5 mL/min. Comparing to the control experiment, the hydrogen peroxide production decreased by 53% in presence of MC, 49% in presence of DLC and 71% in presence of CTS. The preliminary tests confirmed sorption of sediment particles at the electrodes, which is suspected to cause a decrease of the electrodes’ active area and, therefore, limits the production of chemical species involved in hydrogen peroxide formation (oxygen and hydrogen from water electrolysis). Further, we are investigating other inhibition pathways, as well as the influence of additional redox-species from sediments such as Fe and Mn that may be responsible for hydrogen peroxide activation to hydroxyl radicals: a favorable pathway that supports creation of oxidizing conditions.