Aerobic denitrification with an electrode as the sole electron and energy source

Abstract

Biological nitrogen removal from water and wastewater typically requires separate processes for nitrification and denitrification due to the different oxygen concentration requirements of these processes. However, in a simpler and more economic approach, denitrification can occur under aerobic conditions if a suitable electron donor is available. While organic compounds have traditionally been used as electron donors for aerobic denitrification, this study explores the application of an electrode as the sole electron donor and energy source for denitrifying bacteria in the presence of oxygen. This approach enables simultaneous nitrification and denitrification in a single vessel, even in the absence of organic carbon. Results indicate that nitrate removal rates are higher under aerobic conditions than under anaerobic conditions, owing to the higher respiration rate of the involved bacteria. Electron flux analysis reveals that each bacterium reduces nitrate preferentially over oxygen. Notably, the electrochemical potential for aerobic denitrification with an electrode as the electron donor is higher than that for anaerobic denitrification, which could increase the power output of microbial electrochemical technologies. These findings expand the potential applications of aerobic denitrification and highlight the promising use of electrodes as electron donors for simpler and more efficient nitrogen removal from carbon deficient water and wastewater.