Emerging Feammox Technology: Mechanisms, Biotechnological Applications, and Future Prospects

Feammox, an innovative and energy-efficient biological ammonium removal technology, has attracted significant attention in recent years. Defined as the anaerobic ammonium oxidation coupled with Fe(III) reduction, Feammox involves Fe(III)-reducing microbes that oxidize ammonium to nitrite using ferric ions. Identified in diverse ecosystems, such as freshwater, marine, natural wetlands, and wastewater ecosystems, Feammox plays a vital role in the global nitrogen cycle. Numerous studies have investigated its performance, influencing factors, reaction mechanisms, and engineering applications. However, our understanding of the functional microorganisms and key genes involved in Feammox remains limited and controversial. Clearly identifying and characterizing the functional microorganisms responsible for the Feammox process are essential for its practical application in wastewater treatment. Therefore, this review critically analyzes and summarizes recent advances in Feammox research, with a focus on functional microorganisms, key genes, and regulation strategies. Initially, the review discusses the functional microorganisms of Feammox from the perspective of microbial cooperation. It then delves into the enzymatic and genetic mechanisms involved as well as the critical factors affecting Feammox microbial activity. Finally, regulation strategies to enhance the Feammox efficiency are systematically outlined. This comprehensive analysis of current Feammox research provides a clearer and more complete understanding of microbial Feammox, deepens the knowledge of its mechanisms, and establishes a solid foundation for its engineering application.