Microbial electrochemical driven anaerobic ammonium oxidation coupling to denitrification in a single-chamber stainless steel reactor for simultaneous nitrogen and carbon removal.

Anodic ammonium oxidation mainly focuses on autotrophic process, and the removal combined with organic matter oxidation is still unclear in microbial electrolysis cell (MEC). Here, a stainless-steel tank is constructed as an MEC for anaerobic ammonium oxidation and organic matter removal. Results show that MEC increases ammonium oxidation from 3.83 ± 2.51% to 32.90 ± 3.39%, and the organic matter removal rises from 75.69 ± 0.59% to 92.12 ± 0.57%, and the energy consumption is only 0.80 ± 0.09 kWh kg-1N, indicating an energy-efficient approach for simultaneous ammonium and carbon removal. Cyclic voltammetry reveals two pairs of oxidative peaks (-0.4 V and + 0.6 V) which demonstrate the electrochemical activity of biofilms for organic matter and ammonium oxidation, respectively. 16S rRNA gene analysis clarifies the anodic biofilm mainly enriched by the genus of Azoarcus, Hydrogenophaga and Paracoccus. Further analysis indicates that anodic potential controls the community succession of heterotrophic and hydrogenotrophic denitrifying bacteria, and then regulates the nitrogen and carbon removal processes, which extend the insights of anodic anaerobic ammonium oxidation coupling to denitrification under organic conditions.