Progress in low‐temperature partial nitritation/anammox coupled with enhanced biological phosphorus removal: Development, mechanisms, and optimization strategies

Abstract With increasing concerns over eutrophication control and carbon‐neutral wastewater treatment, simultaneous nitrogen and phosphorus removal under low‐temperature conditions remains a critical challenge. Conventional biological nutrient removal processes suffer from high energy demand, external carbon requirements, and excessive sludge production, with significantly reduced efficiency at low temperatures. Partial nitritation/anammox (PN/A) has emerged as a promising low‐carbon nitrogen removal technology due to its low oxygen demand, limited carbon requirement, and low sludge yield. However, coupling PN/A with enhanced biological phosphorus removal (EBPR) under low‐temperature conditions remains difficult because of complex microbial interactions and process control challenges. This review summarizes the development, mechanisms, optimization strategies, and engineering perspectives of low‐temperature PN/A‐based phosphorus removal systems. The transition of PN/A from sidestream applications to mainstream nitrogen–phosphorus removal is discussed, followed by analysis of low‐temperature impacts on key microorganisms, including AOB, AnAOB, and PAOs. The effects of temperature reduction on nitrite conversion, phosphorus metabolism, substrate competition, microbial niche distribution, extracellular polymeric substances, membrane characteristics, enzyme activity, and energy metabolism are critically evaluated. Recent enhancement strategies, including microbial acclimation, functional materials, carrier‐based biofilm optimization, dissolved oxygen regulation, and intelligent control, are further discussed with respect to their mechanisms, limitations, and applicability. Finally, major engineering challenges, including microbial stability, scale‐up validation, environmental adaptability, and advanced monitoring, are highlighted. This review provides a mechanistic framework integrating microbial adaptation, ecological regulation, and process optimization for sustainable low‐temperature PN/A‐based nitrogen and phosphorus removal.