Simultaneous electricity generation and pollutant removal in microbial fuel cell with denitrifying biocathode over nitrite

• An MFC was successfully started up using nitrite as cathodic electron acceptor.
• The optimal HRT was deemed to be 8 h in this study.
• The suitable temperature for power generation was found to be 20 °C.
• The suitable temperature for pollutant removal was found to be 25 °C.
• Free buffer led to 50% decrease of TN removal rate and power generation.

The influences of hydraulic retention time, temperature and free buffer on the performance of short-cut denitrifying microbial fuel cell were investigated after it was successfully started up using nitrite as the cathodic electron acceptor. The results revealed that a power density of 8.3 ± 0.5 W m−3 NC was obtained after 15 days operation. The desirable hydraulic retention time was found in this study to be 8 h, with a COD removal rate of 2.117 ± 0.006 kg m−3 NC d−1 and a total nitrogen removal rate of 0.041 ± 0.002 kg m−3 NC d−1, respectively. It demonstrated that temperature had different effects on the electricity generation and pollutant removal performance of microbial fuel cell. The suitable temperature for power generation and pollutant removal was found to be 20 °C and 25 °C, respectively. Free buffer led to 50% decrease of both total nitrogen removal rate and power density of microbial fuel cell compared to that with phosphate buffer solution addition. The optimal total nitrogen removal rate obtained in the case with sodium azide addition (0.075 ± 0.008 kg m−3 NC d−1) increased by 50% as compared to that without sodium azide addition. It suggested that abolishing oxygen or inhibiting nitrite oxidizing bacteria would favor nitrogen removal.