Analysis Of Purification Effect And Bacterial Community Structure Of Different Process Units In A Water Purification Plant

Drinking water sources in China were generally polluted,In response to the pollution of water sources,relevant research on water purification technology had been carried out and achieved certain effectiveness.In the early phase,the research was focused on the development of single technology which lacked representativeness,integration and systematicness.After the implementation of the National Major Science and Technology Project of Water Pollution Control and Management in China,attention began to be paid to the systematic research on the safety of drinking water,and extensive engineering demonstrations were carried out during the"Eleventh Five-Year Plan"and"Twelfth Five-Year Plan"period.This article took a water supply plant with a water demonstration project in the north during the"Twelfth Five-Year Plan"period as the research topic,and the purification effect of conventional-O₃-BAC advanced treatment process and conventional treatment process running simultaneously in the water plant was compared for one year.Based on the biological function was the key to the persistent removal of pollutants such as organic matter and ammonia nitrogen in some certain process units,in order to figure out the internal mechanism of the pollutant removal in each process unit of water plant,high-throughput sequencing technology was used to study the microbial community structure and its spatiotemporal variation in each unit of the two groups of process in summer and winter.The correlation between microbial community structure and pollutant treatment efficiency was explored,and the correlation between environmental factors and the effluent of each unit and dominant bacteria genus was investigated,so as to provide basis and guidance for further optimizing the operation and management of the water plant process.The specific research results were as follows:Based on the characteristics of raw water with low turbidity and micro-organic pollution,the removal efficiency of pollutants between conventional-O₃-BAC advanced treatment process and conventional process was compared.The results showed that the average removal rates of permanganate index,UV₂₅₄ and turbidity by conventional process were 21.7%,26.8%and 81.8%,respectively,while 38.4%,66.3%and 90.8%by conventional-O₃-BAC advanced treatment process,respectively.The ozone-activated carbon combined process was beneficial to remove organic matter in water,and the two groups of process all had good treatment efficiency on the removal of ammonia nitrogen and nitrite nitrogen,and there was no significant difference in the pollution removal capacity.The decontamination ability of each unit in the two groups of process was explored.The results showed that purification effect of the coagulation and sedimentation in the conventional process was limited due to the characteristics of low temperature and turbidity of raw water,and the removal of pollutants mainly depended on the sand filter.the removal efficiency of organic matter and nitrite was improved in high temperature period in summer,and the removal efficiency of turbidity and ammonia nitrogen was not affected by seasonal variation.In the conventional-O₃-BAC advanced treatment process,each unit had certain removal effect on organic matter,mainly in coagulation-sedimentation unit and ozone-activated carbon unit;Turbidity was mainly removed by conventional process units,ammonia nitrogen was mainly removed by coagulation-sedimentation,carbon filter and sand filter,and nitrite nitrogen was mainly removed by ozone oxidation unit.High-throughput sequencing technology was used to study the whole change of microbial diversity and biological risk during two groups of process,the results showed that bacteria community diversity of the water and filter biofilm in summer was significantly higher than that in winter,while which of advanced treatment process was higher than that in conventional process,coagulation-sedimentation unit had little impact on the bacterial community,granular activated carbon,sand filtration and disinfection units were main affecting process units on bacteria community diversity and composition.In the water samples,the composition of bacterial community showed certain seasonal changes,and the dominant bacteria mainly included Actinobacteria,Proteobacteria,Cyanobacteria,etc.At the genus level,Hgcl＿clade,CL500-29＿marine＿group and Cyanobium＿PCC-6307 were the dominant bacterial genera in water samples.A variety of pathogens or conditional pathogenic bacteria were detected,which included Legionella,Mycobacterium,Acinetobacter and Bacillus,etc.The abundance of pathogenic bacteria in disinfection effluent in winter was higher than that in summer,and which of conventional process was higher than that in advanced treatment process.So Extra attention should be paid to microbiological risk of conventional process effluent in winter.The main factors affecting the bacterial community in drinking water treatment process were p H,temperature and dissolved oxygen.The community structure and function of biofilm were analyzed at different levels.The results indicated that the dominant phyla in biofilm samples were Proteobacteria,Chloroflexi and Acidobacteria,andα-Proteobacteria was the absolute dominant at the class level.At the genus level,the dominant bacteria genera were mainly norank＿f＿A4b,unclassified＿Caldilineaceae,unclassified＿Saprospiraceae,Blastocatella,Cyanobium PCC-6307,Hyphomicrobium,Sphingorhabdus,Pedomicrobium,etc.The dominant bacteria were mostly obligate aerobic or facultative anaerobic bacteria,which were beneficial to the removal of organic pollutants in water.Meanwhile,Nitrospira and other functional bacteria were found,indicating that the filter also had the function of biological reduction and removal of ammonia nitrogen.In this paper,the purification effect and the biological function in common water purification process were studied more deeply.The relevant research results provided theoretical support for the water purification plant to further explore the optimal operation of the process combined with the biological effect,which had positive significance for ensuring the safety of drinking water.