Effects of temperature on biofiltration of ammonia-containing waste gas: Removal efficiency, nitrous oxide...

Ammonia (NH₃) is a key odorous gas emitted from livestock and poultry farming, and biofiltration has been widely used for NH₃ removal. Temperature plays a critical role in regulating microbial activity and greenhouse gas emissions in biofilters. This study comprehensively evaluated the effects of temperature on biofilter performance by maintaining three identical biofilters at 5 °C, 15 °C, and 25 °C using external heating sleeves throughout 91 days experiment. The results showed that NH₃ efficiency was significantly higher at 15 ℃ and 25 ℃ (>93.1 %) than at 5 ℃ (80 %), with no significant difference between 15℃ and 25 ℃. However, N₂O generation was the highest at 25℃, significantly higher than that at 15℃ and 5℃. Quantitative PCR revealed that the amoA of ammonia oxidizing bacteria (AOB) genes copies increased with temperature, explaining the enhanced nitrification at 15 °C and 25 °C. The nitrite accumulation ratio was significantly elevated at 25 °C, indicating a decoupling between AOB and nitrite oxidizing bacteria activities under high temperature conditions. Microbial community analysis indicated that Nitrosomonas was the ubiquitous and the dominant AOB across all the temperature treatments, as the core functional microorganism mediating nitrification and nitrifier denitrification in biofilter systems, the universal dominance of Nitrosomonas reflects its competitive advantage under high-ammonia conditions. The denitrifer communities shifted from Pseudomonas at 5 °Ctoward thermotolerant genera (Luteimonas and Roseateles). These findings demonstrate that maintaining biofilter temperature around 15 °C can achieve high NH₃ removal with minimal N₂O emissions, providing practical insights for the sustainable operation of biofiltration systems in agricultural environments.