Electron transfer pathways and kinetic analysis of cathodic simultaneous nitrification and denitrification process in microbial fuel cell system

Abstract

Microbial fuel cell (MFC) is an innovative bioconversion technology for wastewater treatment accompanied with electricity recovery. In this study, a kinetic model was developed base on Activated Sludge Model No.1 (ASM1) to describe electron transfer pathways during the simultaneous nitrification and denitrification (SND) process in the biocathode system of a dual-chamber MFC. The batch running of the dual-chamber MFC system showed that it produced a power density up to 2.96 W m−3 within 48 h, the achieved SND efficiency and autotrophic denitrification ratio in the cathodic denitrification process were up to 87.3 ± 0.8% and 69.5 ± 6.6%, respectively. Meanwhile, by integrating nitrification, autotrophic denitrification, heterotrophic denitrification, organic carbon oxidation, and oxygen reduction in the cathode, the model was able to precisely fit the concentration variations of NH3–N, dissolved oxygen (DO) and chemical oxygen demand (COD) during the cathodic SND process (R2 ≥ 0.9876). The cathode electrons tended to be completely utilized with the increase of autotrophic denitrification ratio in the cathodic denitrification process. When the nitrification rate was enhanced, the autotrophic denitrification would prevail in the competition with the heterotrophic denitrification. In summary, the developed model was confirmed to be effective and reliable for describing the electron transfer pathways and predicting the performance of the nitrogen removal reactions during the cathodic SND process in a double-chamber MFC.