Integrated simultaneous nitrification/denitrification and comammox consortia as efficient biocatalysts enhance treatment of domestic wastewater in different up-flow bioelectrochemical reactors.

Simultaneous nitrification/denitrification (SND) can efficiently deplete NH4+ by using air-exposed biocathode (AEB) in bioelectrochemical reactors. However, the fluctuation of wastewater adversely affects the functional biofilms and therefore the performance. In this work, four up-flow bioelectrochemical reactors (UBERs) with some novel inocula were investigated to improve domestic wastewater treatment. The UBERs exhibited favorable removal of chemical oxygen demand (COD, 95%), NH4+-N (99%), and total nitrogen (TN, 99%). The maximum of current (2.7 A/m3), power density (136 mW/m3) and coulombic efficiency (20.5%) were obtained. Cyclic voltammetry analysis showed all the electrodes were of diversified catalytic reactions. Illumina pyrosequencing showed the predominant Ignavibacterium, Thauera, Nitrosomonas, Geminicoccus and Nitrospira were in all electrodes, contributing functional biofilms performing SND, comammox, and bioelectrochemical reactions. FAPROTAX analysis confirmed twenty-one functional groups with obvious changes related to chemoheterotrophy, respiration/oxidation/denitrification of nitrite and nitrate. Comfortingly, such novel diversified consortia in UBERs enhance the microbial metabolisms to treat domestic wastewater.