Feammox in wastewater treatment: Mechanisms, synergistic interactions and future engineering applications.

Ferric ammonium oxidation (Feammox) has been found to play a non-negligible role in nitrogen loss in nature and artificial reactors, demonstrating a potential alternative pathway for nitrogen removal. Through the comparative analysis among Feammox, nitrification-denitrification, and anaerobic ammonium oxidation, this review systematically elucidates the mechanism, nitrogen removal efficiency, influencing factors of Feammox and its synergistic interactions with traditional other biological nitrogen removal pathways. Besides, the contribution of Feammox to nitrogen loss in natural environments, and the performance, enhancement measures in artificial reactors are summarized. Finally, based on the synergistic interaction of Feammox and nitrification-denitrification, two potential application scenarios are proposed: 1) Feammox combined with constructed wetlands: the Fe (III)/Fe(II) cycling in biological filler loaded iron-biochar enhances the simultaneous removal of NH4+ and NO3-; 2) Feammox combined with A2O sewage treatment plant: fillers loaded with iron-biochar in the anoxic/anaerobic tanks could also enhance co-removal of organics and nitrogen. This review is conducive to a clearer understanding of Feammox. More importantly, it provides some support for future practical applications.