Towards scalable anammox: mechanistic insights and emerging strategies.

Anammox-based systems are promising wastewater treatment processes that utilize anaerobic ammonium oxidation (anammox) bacteria to remove nitrogen. These systems offer energy-efficient and carbon-neutral alternatives to conventional biological treatments but their practical application faces challenges, including limited total nitrogen (TN)-removal efficiency and sensitivity to adverse conditions. Recent research has explored innovative strategies to overcome these limitations, such as multi-metabolic pathway coupling, integration of photocatalysis and bioelectrochemical modules, and modulation of exogenous iron supply (e.g., iron oxides, ferroheme, and magnetite). In addition, mechanisms that support anammox resistance to environmental stressors are being uncovered. This review outlines these advances and proposes tailored engineering strategies to improve the performance and scalability of anammox-based systems and thus facilitate their application in complex wastewater treatment scenarios.