A review on low-temperature denitrification technologies: evolution, mechanisms and prospects for sustainable wastewater treatment

The inhibition of denitrification in low-temperature environments poses challenges for wastewater treatment plants in cold regions to achieve compliance and control costs. The cold tolerance mechanisms of existing technologies remain unclear, limiting their engineering stability and widespread adoption. Simultaneously, the lack of systematic evaluations balancing technical efficacy and economic viability hinders the selection of optimal technologies. Through bibliometrics analysis, mechanism comparison and multidimensional evaluation, this paper outlines trends in low-temperature denitrification technologies. It indicates that research focus has shifted from traditional methods like constructed wetlands and activated sludge to novel technologies such as biofilms, anammox and solid-phase denitrification (SPD). Among these, SPD and partial denitrification/anammox (PD/A) show promise as advanced solutions combining environmental effectiveness and economic sustainability. SPD achieves a high nitrate removal rate of 91 ± 4% by enriching functional microorganisms, enhancing enzyme activity and accelerating electron transfer, demonstrating outstanding environmental effectiveness. PD/A constructs a more efficient denitrification pathway, circumventing low-temperature limitations on Nir and Nos activity, holding potential for energy conservation and emission reduction. Future priorities should focus on leveraging artificial intelligence to optimize the composite carbon source ratios in SPD for enhanced economic efficiency and employing biofilm/granular sludge to enrich aerobic ammonium-oxidizing bacteria for scalable PD/A.