Enhanced denitrification through microbial and steel fuel-cell generated electron transport

Enhancement of nitrate reduction was studied in a two-chambered microbial fuel cell (MFC) and a similar abiotic fuel cell (steel fuel cell or SFC) with an oxidizable steel wool anode and catalyst-free stainless steel mesh cathode. In the MFC and SFC systems, nitrate was reduced in the cathode chamber at 11.4 or 40.0 mg nitrate/L/day, respectively. The MFC utilized petroleum compounds in refinery wastewater as the electron donor and the SFC utilized steel wool as the electron donor. Oxidation of the petroleum compounds in the MFC and steel wool in the SFC caused electron flow from the anode to the cathode, where nitrate was reduced. Nitrate reduction was significantly (P < 0.001) higher in SFCs with non-sterile groundwater in the cathode chambers and the flow of electrons to the cathode stimulated microbial growth. Our results suggest the both MFC and SFC designs could serve as electron source for nitrate reduction at the cathode. Particularly the SFC could be an innovative low-cost, low-maintenance alternative for in situ remediation of nitrate-contaminated groundwater.