[Simultaneous electricity generation and nitrification in a microbial fuel cell with aerobic biocathode]

The present study demonstrated simultaneous electricity generation and nitrification in a two-chamber microbial fuel cell (MFC) with aerobic biocathode seeded with nitrifying bacteria. Nitrification process and power production simultaneously happening in the same region not only saved energy consumption of aeration by making the best use of oxygen, but also produced additional proton by nitrification process, which effectively prevented alkaline at the cathode caused by power production. The maximum nominal current and maximum power density were 47 mA and 45.50 W/m3, respectively. The NH4+ -N removal rate was 5.98 mg/(L x d) when NH4+ -N concentration was 153.4 mg/L. The nitrifying bacteria competed with electrochemically-active bacteria for oxygen. However, the nitrification was of little effect on bioelectricity production when oxygen concentration was as high as 3.5-5.0 mg/L. The average cathodic voltage with addition of NH4+ -N was 124 mV higher than that of without NH4+ -N addition when no buffer was added in the medium. Cathodic variations were corresponded with nitrification process. The theoretical calculation of H+ ion proved that, the additional H+ ion produced by nitrification process (8.14 x 10(3) mol) was similar with the H+ ion consumed by power production process (8.54 x 10(-3) mol), which confirmed that nitrification could compensate the pH gradient caused by bioelectricity process in the cathode, and maintained the stable pH value to a certain extent.