Simultaneous perchlorate and nitrate removal coupled with electricity generation in autotrophic denitrifying biocathode microbial fuel cell

In this study, an autotrophic denitrifying biocathode was investigated to couple the reduction of nitrate or/and perchlorate with electricity generation. Results showed that when the current density in microbial fuel cell (MFC) with sole perchlorate and sole nitrate as the substrate stabilized at 3.00 and 1.52 mA/m3 respectively, the perchlorate and nitrate removal efficiency achieved 53.14% and 87.05%. As influent molar ratio of NO3−/ClO4− was 1:1, the stable current density reached the a peak value (3.10 A/m3) accompanied by the maximum integral mixed substrate removal (40.97% for ClO4− and 86.03% for NO3−). Open and close circuit experiments demonstrated that the nitrate and perchlorate removal should be ascribed to the bioreduction of autotrophic denitrifying biocathode. Cyclic voltammetry (CV) curves showed that all of biocathodes had strong electrochemical activity and there were few clear distinctions of redox potential between the biocathodes fed with different substrates. Results of 16S rRNA sequencing revealed a predominance of β-Proteobacteria in the autotrophic denitrifying biocathode, which is a well-known environmental nitrogen cycler.