Functional biological anode as electron acceptor for direct oxidation of ammonia nitrogen to N2 in an anaerobic single-chamber reactor

A functional biological anode (nonwoven-wrapped functional microbial carbon felt bag) was constructed to realize the ammonia oxidation to nitrogen gas in a single-chamber anaerobic microbial electrochemical system (MES). The applied potential has a significant impact on oxidation products of ammonia. As the applied potential was reduced from +0.8 V to +0.3 V (vs. Ag/AgCl), the ammonia oxidation rate increased from 65.2% to 94.7% and the TN removal rate increased from almost 0 to 88.0% on the bio-anode. At +0.3 V ammonia could be converted to N2 on the bio-anode and hydrogen is generated on the cathode. The zeolite adsorbent added inside the anodic carbon felt bag was also a key factor to accelerate nitrogen removal in the MES. The dominant genera of SWB02 sp., Nitrospira sp. and Bryobacter sp. played a crucial role in ammonia oxidation according to 16S rRNA analysis. This paper provides a new idea for NH4+-N removal and hydrogen production from wastewater.