SRP402959 PRJNA891044 Enhancement of N removal by electrification coupled by Feammox and Fe(II)/Fe(III) cycle in wastewater treatment Ammonium (NH4+) is a known toxic nitrogen pollutant in wastewater and causes serious deterioration of water quality when discharged without treatment. Feammox, Fe(III) reduction coupled with ammonium oxidation (Anammox), is a new promising NH4+ removal pathway. However, the low efficiency of Feammox limits its application in wastewater treatment. In this study, NH4+ removal efficiency by Feammox was promoted by introduction of Fe2O3 and AQDS (Anthraquinone-2,6-disulfonic acid) as electron shuttling molecules with and without electrification in two batch experiments Rn(Fe2O3+AQDS) and Re(Fe2O3+AQDS+electrification). Results from this study showed that NH4+ removal was significantly enhanced under electrification, with the efficiency increased up to 74.3% by day 34. Based on microbial community analysis by High Hrough-put sequencing, both the FeRB and denitrification bacteria were promoted in their relative abundance under electrification. Genus of denitrification bacteria Citrifermentans, Klebsiella, Legionella, Clicycliphilus and Ciaphorobacter were confirmed by their Feammox function for the first time since they were closely related clustered with Feammox bacteria from the phylogenetic tree. The high efficiency of NH4+ removal was accelerated by Fe(II)/Fe(III) cycling under electrification and mediated by the combination of FeRB, NDFO and denitrifying bacteria coupled with Feammox process in the reactors. This study provided new evidence and revealed insightful functional microbial groups for enhanced Feammox process in ammonium-rich wastewater treatment with amendment of ADQS under electrification.