Abstract：To enhance the biological nitrogen removal efficiency of acidic nitrogen-containing wastewater and improve the adaptability of water treatment microorganisms to acidic water conditions, a "bottom-up" strategy for constructing a nitrogen removal bacterial consortium was adopted. Core strains were selected through statistical analysis and partial factorial experiments, and a group of denitrifying composite bacteria, S119-S136-L22, was rationally designed and constructed around these core strains. Under conditions of pH 4.0 and an initial nitrate nitrogen (NO3--N) concentration of 200mg/L, the nitrate removal rate reached 97.32% after 36hours. Through whole-genome sequencing combined with analysis of genes related to nitrogen metabolism and denitrification in each strain, it was speculated that strains S136 and L22 in the consortium are mainly responsible for reducing NO3--N to nitrite nitrogen (NO2--N), while S119 was responsible for reducing NO2--N to nitrogen gas (N2). Sequencing batch reactor (SBR) studies showed that the removal rates of NO3--N and total nitrogen (TN) in the experimental group were increased by 28.99% and 28.67%, respectively, compared to the control group. High-throughput sequencing and analysis of the microbial community interaction network in the system indicated that, compared to the control group, two additional functionally distinct bacterial genera, Cloacibacterium and Serratia, emerged in the experimental group, along with Enterobacter, Alcaligenes, and Klebsiella. The experimental group exhibited a more complex and diverse network of positive correlation pathways, not only showing synergistic interactions between the bacterial genera within the composite consortium but also collinearity between Serratia, Acinetobacter and Achromobacter, as well as between Cloacibacterium, Macellibacteroides and Pleomorphomonas. Analysis of the interaction network between effluent TN, NO3--N, and the microbial community revealed that Cloacibacterium primarily drives the removal of TN and NO3--N, while Pleomorphomonas, Microbacterium, and Propionicicella also play important roles in the removal process of TN and NO3--N.
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