Complete nitrogen removal and electricity production in Thauera-dominated air-cathode single chambered microbial fuel cell

Electrochemically active bacteria (EAB) usually catalyze the electrochemical reactions on the electrodes of microbial fuel cells (MFCs) to fulfill organic oxidation and electricity generation. In this work, an aerobic consortium of Thauera-dominated denitrifiers was investigated in anaerobic single chambered MFC (SCMFC) for simultaneous electricity generation and pollutants removal. Using a batch regime feeding COD (240 mg L-1) and ammonia (130 mg L-1), the removal efficiencies of COD, ammonia and total nitrogen (TN) obtained highly at 90%, 98%, and 95%, respectively, and a maximum power output of 1250 +/- 20 mWm(-2) was found. High-throughput sequencing illustrated that the dominant species at the anode was Thauera (75% abundance), indicating its important role in oxidation reactions and electron transfer. At the water-facing side of the air cathode, the predominated bacteria were Thauera (43-74%), Nitrosomonas (3-8%), Desulfomicrobium (1-8%) and Thiobacillus (3-5%), which are involved in nitrification/denitrification process. It can be inferred that complete nitrogen removal may facilitate simultaneous nitrification/denitrification with such inoculum. Furthermore, cyclic voltammetry measurements showed obvious oxidation peaks at -0.40 V and +0.60 V, which indicated that the anode with Thauera-dominated consortium could efficiently catalyze oxidation reactions of organic matter for current generation and nitrogen removal. Therefore, it was demonstrated that to introduce the Thauera-dominated aerobic denitrifying consortium into MFCs is a new and promising approach to enrich EAB for wastewater treatment.