The relationship between energy production and simultaneous nitrification and denitrification via bioelectric derivation of microbial fuel cells at different anode numbers.

In this study, three microbial fuel cells (MFCs) with different numbers of anodes (i.e., 1A, 3A, and 5A) were constructed to study the effects of a multi-anode (MA) system on power generation performance and nitrogen (N) removal from low carbon (C)/N wastewater. The maximum power density of 3A-MFC was 236.7 mW m-3, which was 2.6-fold and 1.2-fold that of 1A-MFC and 5A-MFC, respectively. The 3A-MFC system produced the highest total energy output in one cycle, approximately 41.7 mW h, which was 1.5-fold and 1.3-fold that of 1A-MFC and 5A-MFC, respectively. 3A-MFC also had the highest total N (TN) removal efficiency (71.1 ± 3.9%) and simultaneous nitrification and denitrification (SND) rate (93.5 ± 2.4%). An analysis of electron flow distribution in the 3A-MFC biocathode showed that electro-autotrophic denitrification accounted for 19% of the total denitrification in the last 135 h. Thereafter, the relationships between TN removal, anode number, and bioelectricity were systematically evaluated. TN removal efficiency had a good linear relationship with energy production (R2 = 0.97539); TN removal was mainly dependent on SND. Generally, the MA-MFC configuration proposed in this study produced more electrical energy and improved TN removal by enhancing nitrification and heterotrophic and electro-autotrophic denitrification of the biocathode. The proposed method is therefore effective for enhancing N removal.