Study On The Cluster Analysis And Functional Bacteria Distribution Characteristics Of Urban Sewer System

A series of biological and chemical reactions will take place in the process of sewage transportation in municipal sewage pipe network.Microbial community will participate in biochemical reactions and bring dangerous gas emissions to the pipe network.In this paper,cluster analysis method is introduced into the study of microbial community distribution in sewage pipe network.The complex actual sewage pipe network is simplified and classified.Based on the classified characteristic pipes,field investigation is carried out.The distribution characteristics of microbial community in sewage pipe network are analyzed from the aspects of microbial diversity,phylum and genus level.The relationship between microbial community structure in biofilm of water head and sewage pipe network is analyzed the microbial community structure of biofilm in the net was compared and analyzed.Combined with water quality and environmental factors,the relationship between microbial community and water quality indicators and environmental factors was explored.Firstly,the actual sewage pipe network was investigated,the characteristic parameters of sewage pipe were collected,and the sewage water quality indexes were detected.It was found that the actual sewage pipe network situation was complex.If the water quality and microbial community of a certain pipe were analyzed,there was no rule to follow.In order to solve this problem,K-means clustering analysis was used to simplify and classify the complex municipal sewage network.The results showed that the actual sewage pipe network in this study was suitable for k=4 mean clustering algorithm to classify the characteristics of sewage pipe network.In the area of 4.5 square kilometers,it was suitable to cluster the pipe network into four types of characteristic pipe segments to study the distribution of microbial community.I pipe and IV pipe can be regarded as the first section and the end of the sewage pipe network respectively.The main characteristics of class I-IV pipe are that the pipe sections receive less and less fresh sewage discharged from buildings along the way,the number of branch pipes converging in was increasing,the epidemic time of sewage in the pipe was getting longer and longer,the pipe diameter was gradually increasing,and the chemical oxygen demand in the water quality index was reduced from 700-1000 mg/L to 100-300 mg/L.Total nitrogen and ammonia nitrogen decreased from 70-100 mg/L,60-90 mg/L to 30-50 mg/L,30-40mg/L respectively;total phosphorus decreased from 7-10 mg/L to about 3 mg/L.Based on the results of the cluster analysis of the sewage pipe network,the municipal sewage pipe network of a certain city in Shaanxi Province was taken as the research object.Sampling points were selected for each type of pipe section,and the biofilm in the wet junction area of the inner bottom of the pipe was collected for biological phase detection to explore the actual situation,and the distribution characteristics of functional bacteria in the sewage pipe network.The results of PCA analysis based on the Alpha diversity of bacteria and archaea showed that the results after cluster analysis of the sewage pipe network are reasonable.At the genus level,carbon cycling bacteria were mainly fermenting bacteria,and the most obvious fermenting effect was found in type II and type III segments;Among the sulfur cycling bacteria,desulfobulbus has always been in the dominant position in the pipe network,and the class I and class II pipe sections are likely to produce high concentration of hydrogen sulfide;The dominant species of nitrogen cycling bacteria changed from Acinetobacter to Acidovorax;Methanothrix was the dominant genus in methanogens,which indicated that methane emission may threaten the four types of pipe segments.In addition,the distribution differences of microorganisms in the water source and sewage pipe network were compared,and a large number of functional bacteria were found,which indicated that organic matter transformation had begun in the building drainage riser,providing nutrients for the microorganisms in the front of the pipe network.The water quality in different types of pipe sections was tested,and it was found that the decrease in the total phosphorus content in the pipe network may be caused by the sedimentation of particulate matter.Spearman and RDA analysis of water quality indicators,environmental factors and dominant bacterial communities showed that water quality indicators have a great influence on the changes of microbial communities in Class I and II pipe,while environmental factors had an impact on the changes in microbial communities in III and IV pipe.The order of water quality indicators and environmental factors’influence on microorganisms was NH₃-N>ORP≈COD>TP,pipe diameter≈water depth>flow velocity≈fullness.