Metagenomic Analysis of Bacterial Community Structure and Pollutant Removal Process in High-Altitude Municipal Wastewater Treatment Plants of Tibet, China

The bacterial communities of activated sludge are correlative with influent characteristics, geographical discrepancies, and environmental variables, which are essential for wastewater treatment plants (WWTPs). However, the comprehensive deciphering of bacterial community diversity in high-altitude WWTPs is scarce in Tibet, China. This study collected activated sludge samples from four A2O WWTPs (2980–3650 m above sea level) in Tibet. Illumina NovaSeq high-throughput sequencing revealed that Proteobacteria was the most abundant phylum (46.2–62.9%), followed by Bacteroidetes (14.8–21.8%) and Actinobacteria (3.5–10.9%). Candidatus Accumulibacter (7.2–15.1%) was the dominant denitrifying polyphosphate-accumulating organisms (DPAOs). Moreover, a principal coordinate analysis (PCA) revealed strong correlations between environmental factors and dominant phyla, while Candidatus Accumulibacter as a dominant genus was unaffected by environmental factors. Additionally, the reaction mechanisms were analyzed based on the functional gene abundance of carbon, nitrogen, and phosphorus metabolic pathways in high-altitude WWTPs. The carbon metabolism pathway, especially carbohydrate metabolism (14.52%), has more abundant functional genes in Nyingchi (LZ). Nitrogen metabolism mainly consists of assimilatory nitrate reduction, dissimilatory nitrate reduction, and denitrification; the high abundance of functional genes in phosphorus metabolism ensures efficient phosphorus removal. The obtained microbial information in the WWTPs could provide essential guidance for the sustainable management of wastewater treatment systems in high-altitude environments. Future research should focus on monitoring the seasonal dynamics of bacterial communities in high-altitude WWTPs and responses to environmental disturbances, to optimize treatment efficiency and ensure long-term sustainability.