This study addresses the challenges of low efficacy and microbial activity in low-temperature municipal wastewater treatment by utilizing an air-lift micro-pressure internal circulation integrated reactor (AMICIR). The reactor creates alternating aerobic and anaerobic environments to explore the enrichment conditions of aerobic denitrifying bacteria, examine pollutant removal efficiency, and analyze bacterial colony structure. The results show that the average removal rates of NH4+-N, COD, TP, and TN reached 93.85%, 89.30%, 92.75%, and 75.4%, respectively. Microorganisms secreted large amounts of proteins and polysaccharides, forming zoogloea and creating anaerobic microenvironments conducive to denitrification. IlluminaMiSeq sequencing revealed the presence of anaerobic phyla, and the system enriched a large number of microorganisms, including aerobic denitrifying bacteria such as Flavobacterium, Rhodoferax, and Pseudomonas. Functional gene prediction indicated high abundance of aerobic denitrification genes, such as napA. The study demonstrates that aerobic denitrifying bacteria can be successfully enriched in the system to improve nitrogen removal from municipal wastewater at low temperatures.This study addresses the challenges of low efficacy and microbial activity in low-temperature municipal wastewater treatment by utilizing an air-lift micro-pressure internal circulation integrated reactor (AMICIR). The reactor creates alternating aerobic and anaerobic environments to explore the enrichment conditions of aerobic denitrifying bacteria, examine pollutant removal efficiency, and analyze bacterial colony structure. The results show that the average removal rates of NH4+-N, COD, TP, and TN reached 93.85%, 89.30%, 92.75%, and 75.4%, respectively. Microorganisms secreted large amounts of proteins and polysaccharides, forming zoogloea and creating anaerobic microenvironments conducive to denitrification. IlluminaMiSeq sequencing revealed the presence of anaerobic phyla, and the system enriched a large number of microorganisms, including aerobic denitrifying bacteria such as Flavobacterium, Rhodoferax, and Pseudomonas. Functional gene prediction indicated high abundance of aerobic denitrification genes, such as napA. The study demonstrates that aerobic denitrifying bacteria can be successfully enriched in the system to improve nitrogen removal from municipal wastewater at low temperatures.