The potential of electrotrophic denitrification coupled with sulfur recycle in MFC and its responses to COD/SO42- ratios.

Abstract Electrotrophic denitrification is a promising novel nitrogen removal technique. In this study, the performance and the mechanism of electrotrophic denitrification coupled with sulfate-sulfide cycle were investigated under different anodic influent COD/SO42− ratios. The results showed that electrotrophic denitrification contributed to more than 22% total nitrogen removal in cathode chamber. Higher COD/SO42− ratios would deteriorate the sulfate reduction but enhance methane production. Further mass balance indicated that the electron flow utilized by methanogenic archaea (MA) increased while that utilized by sulfate-reducing bacteria (SRB) decreased as the COD/SO42− ratio increased from 0.44 to 1.11. However, higher COD/SO42− ratios would produce more electrons to strengthen electrotrophic denitrification. Microbial community analysis showed that the biocathode was predominantly covered by Thiobacillus that encoded with narG gene. These findings collectively suggest that electrotrophic denitrification could be a sustainable approach to simultaneously remove COD and nitrogen under suitable COD/SO42− ratio based on sulfur cycle in wastewater.