Sulfur cycle process accelerates microbial fuel cells driven denitrification system: Low sulfate yield and enrichment of functional microorganisms.

The denitrification of dual-chamber microbial fuel cells cathodic chamber driven by sulfur powder has the advantages of economy, efficient and pollution-free. However, the low electron utilization of anodic chamber (ACE) and high sulfate (SO42-) production limit its application. Therefore, the cooperation of calcined pyrite (CP) and γ-FeOOH was proposed to solve the above bottleneck problems (S-CP-γ-FeOOH). The results showed that after adding CP and γ-FeOOH to S system, the nitrate removal rate (NRR) changed from 20.39 ± 0.37 % to 94.11 ± 1.40 %; ACE increased from 11.10 ± 0.76 % to 61.05 ± 7.82 %; and SO42- content decreased by 61.26 %. CP and γ-FeOOH promoted the intra/extracellular electron transfer process. SO42- was reduced to sulfur compounds after γ-FeOOH was added, which improved the electron generation efficiency of the anodic chamber. The addition of CP and γ-FeOOH not only enriched sulfur-oxidizing bacteria and enhanced their metabolic activity, but γ-FeOOH also promoted sulfate-reducing bacteria, all of which improved NRR.