Carbon sources shortage of biological denitrification is a great challenge in municipal wastewater treatment. Bioelectrochemical system (BES) as a new approach for denitrification has not well been established to treat low-C/N wastewater. In this study, the nitrate removal was compared in a traditional anaerobic reactor (R1), two anaerobic reactors with C-C electrodes (R2) and Fe-C electrodes (R3), respectively. The results demonstrated that the electrodes could improve significantly the denitrification at low C/N, and Fe further enhanced its performance. The increased denitrification was a result from the combination of anodic oxidation and cathodic denitrification. The anodic oxidation competed with other heterotrophic processes for utilizing carbon sources to increase denitrification. The higher nitrate removal in R3 was mainly attributed that more exoelectrogenic bacteria were enriched with the presence of Fe to enhance the anodic oxidation and better drive the cathodic denitrification to occur. (C) 2015 Elsevier B.V. All rights reserved.