Simultaneous nitrification, denitrification and carbon removal in microbial fuel cells

Microbial fuel cells (MFCs) can use nitrate as a cathodic electron acceptor, allowing for simultaneous removal of carbon (at the anode) and nitrogen (at the cathode). In this study, we supplemented the cathodic process with in situ nitrification through specific aeration, and thus obtained simultaneous nitrification and denitrification (SND) in the one half-cell. Synthetic wastewater containing acetate and ammonium was supplied to the anode; the effluent was subsequently directed to the cathode. The influence of oxygen levels and carbon/nitrogen concentrations and ratios on the system performances was investigated. Denitrification occurred simultaneously with nitrification at the cathode, producing an effluent with levels of nitrate and ammonium as low as 1.0 ± 0.5 mg N L−1 and 2.13 ± 0.05 mg N L−1, respectively, resulting in a nitrogen removal efficiency of 94.1 ± 0.9%. The integration of the nitrification process into the cathode solves the drawback of ammonium losses due to diffusion between compartments in the MFC, as previously reported in a system operating with external nitrification stage. This work represents the first successful attempt to combine SND and organics oxidation while producing electricity in an MFC.