Study on the Influence of Temperature on Biogas-Coupled Anaerobic Ammonium Oxidation

Temperature is widely recognized as a critical limiting factor for the stable operation of anaerobic ammonium oxidation (Anammox) systems, with low-temperature environments typically imposing severe inhibition on the metabolic activity of functional anaerobic ammonium oxidation bacteria (AnAOB) and the overall nitrogen removal performance. While Anammox has emerged as a promising low-carbon nitrogen removal technology for wastewater treatment, its full-scale application in temperate and cold regions is largely constrained by low-temperature suppression, and the mitigation potential of biogas coupling in this context remains poorly elucidated. To address this knowledge gap, this study systematically investigated the alleviation effect of intermittent biogas injection on low-temperature inhibition of Anammox systems under a gradient of temperature conditions (30°C, 25°C, and 20°C) using upflow anaerobic sludge blanket (UASB) reactors. Results demonstrated that the experimental reactor with intermittent biogas injection exhibited significantly superior nitrogen removal efficiency and long-term operational stability compared with the non-biogas control group at each tested temperature. Specifically, the total nitrogen removal efficiency of the biogas-amended reactor remained as high as 74.83% at 20°C, which was markedly higher than that of the control group. Mechanistic investigations revealed that intermittent biogas injection optimized the physicochemical characteristics of Anammox granular sludge, slowed the attenuation of specific Anammox activity (SAA), and enriched the dominant AnAOB genus Candidatus_Kuenenia via three synergistic pathways: continuous inorganic carbon supply from CO₂ dissolution, pH buffering capacity, and shear force regulation. Collectively, these effects significantly enhanced the low-temperature resistance and operational resilience of the Anammox system. This work provides critical mechanistic insights and technical support for the stable operation of Anammox-based processes in low-temperature regions, advancing the practical application of low-carbon nitrogen removal technologies.