| In the process of pollutant transformation and decomposition in water,the complex microbial community in the sewage treatment system plays a key role.Based on the actual operation and management project of Zhoucun Town Integrated Wastewater Treatment Plant,this paper analyzes the microbial community structure,functional genes and metabolic potential of the wastewater treatment system through metagenomic sequencing technology.The main results are as follows :(1)During the long-term operation of the sewage plant,the average concentrations of chemical oxygen demand,ammonia nitrogen,total nitrogen,total phosphorus and suspended solids in the effluent were 20.5 mg/L,0.36 mg/L,11.29 mg/L,0.17 mg/L and 6.71 mg/L,respectively.The average removal rates were 90.95%,98.2%,62.12%,92.03% and 97.1%,respectively.All indicators can stably meet the new local environmental protection regulations.(2)Proteobacteria,Bacteroidetes and Firmicutes were the dominant bacteria in the influent and their relative abundances were 64.58%,14.37% and 13.49%,respectively.Thauera,Arcobacter and Bacteroidesa were the dominant bacteria in the influent and their relative abundances were 14.34%,6.98% and 6.72%,respectively.Proteobacteria,Actinobacteria,Chloroflexi and Nitrospirae were the common dominant bacteria in the activated sludge of A and B sections and oxidation ditch,and their relative abundances were44.26%–48.78%,11.18%–15.63%,12.02%–12.47%,5.68%–8.35%,respectively.The common dominant bacteria in the activated sludge of A and B sections and oxidation ditch were Nitrospira,Hyphomicrobium and Thauera.There was little difference in the species composition of activated sludge in A,B and oxidation ditch.The dominant bacteria in the effluent of the oxidation ditch sedimentation tank and the B-stage sedimentation tank were Nitrospira,Thauera,and Hyphomicrobium,and their relative abundances were9.36%–10.42%,4.52%–6.79%,and 2.49%–3.34%,respectively.(3)The KEGG functional annotation results of the whole sewage treatment system genes showed that the gene function was mainly related to Metabolism,followed by the number of functional genes related to Cellular Processes,Genetic Information Processing and Environmental Information Processing.Among the functional genes related to metabolism,carbohydrate metabolism,amino acid metabolism,energy metabolism and nucleotide metabolism were mainly involved,and the number of functional units related to these four metabolic pathways was 357800,273297,17702 and 140204,respectively.There is little difference in functional level between A section,B section and oxidation ditch,and the sewage treatment system has high consistency in species and functional level.(4)Nitrosomonas,Nitrosopumilus,Nitrospira and Thauera were the dominant AOB,AOA,NOB and denitrifying bacteria in the sewage treatment system,respectively.The relative abundance of AOB,AOA,NOB and denitrifying bacteria in the biological treatment unit was 0.459%–1.523%,0.00436%–0.0867%,10.27%–15.65%,11.38%–15.38%,respectively.A total of 6 functional genes related to the nitrification pathway and 10 functional genes related to the denitrification pathway were annotated in the sewage treatment system,indicating that the sewage treatment system has a complete nitrification and denitrification pathway.Among them,the abundance of nxr A and nxr B was higher,and they were the dominant genes related to the nitrification pathway.The abundance of nxr A and nxr B in the biological treatment unit was 371.905–383.96 CPM,161.47–181.08 CPM;the abundance of nar G and nar H was higher,and they were the dominant functional genes related to the denitrification process.The abundance of nar G and nar H in the biological treatment unit was 371.905–383.96 CPM and 161.47–181.08 CPM,respectively.Pseudomonas and Paracoccus were the dominant phosphorus metabolism bacteria.The relative abundance of various phosphorus metabolism functional bacteria in A,oxidation ditch and B section was2.902%,2.292% and 2.705%,respectively.The high abundance of pat B,pat,phn A and phn P is the dominant functional gene of phosphorus metabolism in sewage treatment system.The absolute abundance of pat B,pat,phn A and phn P in biological treatment unit is 69.59–79.86 CPM,80.51–104.52 CPM,39.76–49.71 CPM,54.09–75.41 CPM,respectively.In this paper,the long-term operation effect of wastewater treatment plant is studied from the level of water quality index.The structure and diversity of microbial flora in wastewater treatment system are studied from the level of species.The gene function and metabolic potential of wastewater treatment system are further elaborated from the functional level,which can provide some theoretical support for the long-term efficient and stable operation of wastewater treatment plant. |
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