Bioelectrochemical Remediation of Nitrate Contaminated Groundwater in Microbial Fuel Cell

Nitrate contamination in groundwater is a growing concern in Wisconsin, due to the increasing concentration in groundwater sources and its intensive application as a fertilizer for agricultural activities. In addition, most people in rural regions rely on groundwater as their primary supply of drinking water. There is increasing interest in groundwater nitrate removal. Traditional in-situ nitrate removal methods include reverse osmosis (RO) and ion exchange resin both of which have a high removal efficiency but are costly for decentralized in-situ treatment. Microbial fuel cell (MFC) is considered as a sustainable and efficient technology for nitrate removal from groundwater. However, in previous studies, groundwater is usually used as the anolyte, which potentially introduces bacteria and other ions into the treated groundwater that requires post-treatment. In this study, we designed a dual-chamber MFC system to remove nitrate ions from groundwater. Groundwater served as the catholyte, and the nitrate ions transported across the anion exchange membrane before being reduced by microorganisms. The system performance was evaluated under different conditions including varying influent nitrate concentrations, chloride concentrations, and external resistance. The kinetics of denitrification in the whole system under different operation condition was computed and the fundamental theory of the system was discussed. Most experiments achieved a high nitrate removal efficiency of greater than 95% when the nitrate concentration ranged from 14 mg L-1 to 56 mg L-1 under various operation conditions. The highest nitrate removal rate showed up when the catholyte influent nitrate concentration was 56 mg L-1. The removal rate of nitrate decreased from 4.77 ± 0.14 mg L-1 hr-1 to 2.41 ± 0.45 mg L-1 hr-1 as the chloride concentration increased from 142 mg L-1 to 710 mg L-1. The nitrate removal rate remained stable though the external resistance varied. When we fed real groundwater into catholyte influent, 90.6 ± 12.1 % of nitrate was removed and the removal rate reached 5.4 ± 0.7 mg L-1 hr-1