Effects of ultraviolet radiation on the community structure and metabolic pathways of A2O process in plateau environment

Water treatment ecosystems provide an important habitat for a variety of bacterial communities, but the mechanisms by which this ecosystem responds to UV irradiation are unclear. For this reason, 16S rRNA gene sequencing was used to study bacterial community structure and metabolic pathways under UV irradiation. It was shown that bacterial communities were different under different UV irradiation, suggesting that the time of UV irradiation has an effect on the structure of bacterial communities. Analysis of the drivers showed that COD, pH, TN and NH3-N also had an effect on the relative abundance of keystone species. The key species under UV irradiation were Bacteroidetes, Proteobacteria, Actinobacteria, Firmicutes, Chloroflexi, and Chlamydiae, accounting for 96.69% to 98.30%, and UV irradiation had a significant inhibitory effect on the relative abundance of key species. Chlamydiae, as the dominant bacterial phylum in the highland environment, was identified for the first time. Network co-occurrence plots constructed under different UV radiation showed that each sample consisted of three independent network plots. There are six common dominant phyla and 33 common dominant bacterial genera in each sample, which reveals that the ecosystem is structured by more similar microorganisms rather than a random phenomenon. This also reflects the competitive relationships between species and the adaptability of bacteria to their environment. The analysis of metabolic pathways revealed that the dominant metabolic pathways in the highland environment changed somewhat under UV irradiation. Further analysis of carbon, nitrogen and phosphorus metabolic pathways showed that there were some changes in the relative abundance of the relevant metabolic pathways, but the differences in the metabolic maps were minimal, i.e., the effects of UV radiation were mainly reflected in the relative abundance of the metabolic pathways. These findings suggest that UV radiation in the plateau environment acts as an important influencing factor on the structure and metabolic pathways of microorganisms. This study provides an important theoretical basis for further understanding of the water treatment ecosystem in the plateau environment, and also provides a new perspective for the study of wastewater treatment systems.