Enhancing bio-cathodic nitrate removal through anode-cathode polarity inversion together with regulating the anode electroactivity

Bio-cathodic nitrate removal uses autotrophic nitrate-reducing bacteria as catalysts to realize the nitrate removal process and has been considered as a cost-effective way to remove nitrate contamination. However, the present bio-cathodic nitrate removal process has problems with long start-up time and low performance, which are urgently required to improve for its application. In this study, we investigated an anode-cathode polarity inversion method for rapidly cultivating high-performance nitrate-reducing bio-cathode by regulating bio-anodic bio-oxidation electroactivities under different external resistances and explored at the first time the correlation between the oxidation performance and the reduction performance of one mixed-bacteria bioelectrode. A high bio-electrochemical nitrate removal rate of 2.74 +/- 0.03 gNO(3)(-)-N m(-2) d(-1) was obtained at the bioelectrode with high bio-anodic bio-oxidation electroactivity, which was 4.0 times that of 0.69 +/- 0.03 gNO(3)(-)-N m(-2) d(-1) at the bioelectrode with low bio-oxidation electroactivity, and which was 1.3-7.9 times that of reported (0.35-2.04 gNO(3)(-)-N m(-2) d(-1)). 16S rRNA gene sequences and bacterial biomass analysis showed higher biocathodic nitrate removal came from higher bacterial biomass of electrogenic bacteria and nitrate-reducing bacteria. A good linear correlation between the bio-cathodic nitrate removal performance and the reversed bio-anodic bio-oxidation electroactivity was presented and likely implied that electrogenic biofilm had either action as autotrophic nitrate reduction or promotion to the development of autotrophic nitrate removal system. This study provided a novel strategy not only to rapidly cultivate high-performance bio-cathode but also to possibly develop the bio-cathode with specific functions for substance synthesis and pollutant detection. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigated an anode-cathode polarity inversion method to rapidly cultivate high-performance nitrate-reducing bio-cathode and found a correlation between the oxidation performance and the reduction performance. The bioelectrode with high bio-anodic bio-oxidation electroactivity achieved a significantly higher nitrate removal rate compared to the bioelectrode with low bio-oxidation electroactivity. The findings provide a novel strategy for enhancing bio-cathodic nitrate removal performance and have potential implications for the development of bio-cathodes with specific functions.