Study On The Microbial Community Structure And Biological Risk In Water Purification Process Unit

Conventional and ozone-biological activated carbon?O₃-BAC?process is widely used in the advanced treatment of potable water,in which the microbial community composition of different unit is complex.The operation accident in the water purification plant or microorganism outbreak would increase the biological risk in the treated water.However,a comprehensive analysis of the group structure of bacterial,fungal and virus in this water purification process is absent.Related research,such as comparative analysis method of common pathogenic bacteria and conditional pathogen in water treatment process,high-throughput rapid detection methods for risk microbes,is very scarce.Emergency disinfection methods for risk microbial outbreaks and predicting methods for main metabolite outbreaks cannot ensure the bio-safety of the treated water.In this regard,our research mainly studied the following contents:The study adopted the method of biodiversity sequencing to analyze the spatial and temporal changes of bacterial community and fungal community during water treatment.A total of 43 phyla,832 genera bacteria and 6 phyla,227 genera fungi were obtained from the water treatment process.The temporal and spatial changes of bacterial and fungal communities in effluent of each unit and the effects of water quality parameters on bacterial and fungal communities were studied.It was found that:compared with seasonal factors,the water treatment process unit had a significant influence on the bacterial and fungal communities.The composition of bacterial and fungal communities in adjacent water treatment units was more similar.Among the water quality indicators,temperature,total phosphorus,total nitrogen,ammonia nitrogen,COD_Mn and others related to microbial nutrition,growth and reproduction had a greater impact on most bacteria and fungi.In water purification unit,ozone oxidation unit and disinfection unit had good removal efficiency on microbial species and abundance.The microbial community structure of carbon filter unit was complex and the abundance distribution was more uniform.Carbon filter unit was the main source of microbial leakage risk in water treatment process.The 16S rDNA full-length gene database including 352 common pathogens and conditional pathogens as well as alignment method was established.The 16S rDNA of 33 common pathogens and conditional pathogens in the water treatment process was found.The number of 16S rDNA sequences accounted for 21.08%of the total number obtained by sequencing.The 16S rDNA of pathogenic bacteria and conditional pathogens?B.cenocepacia,C.Botulinum,NMEC,etc.?presented in the effluent of each unit and maintained a high abundance.The validity and limitation of the comparison method were verified by selective medium.The study showed that:in the process of water treatment,the pathogenic bacteria and conditional pathogens in the hot season were complex.The abundance of some pathogenic bacteria and conditional pathogens?N.meningitidis and C.thermocellum?in the low temperature season was relatively high,which should be paid attention to.The O₃-BAC process had a great influence on the pathogenic bacteria and the pathogenic bacteria community.The carbon filter unit increases the abundance of low-abundance pathogenic bacteria and conditional pathogens.The 16S rDNA of new pathogenic bacteria and conditional pathogens derived from long-term accumulation of biological activated carbon appeared in the unit effluent.These gene fragments may originate from microbial communities attached to biological activated carbon.Based on SISPA-PCR and viral macro-genome sequencing,this study analyzed the virus diversity in raw water and treated water.Practice showed that the viral titer in raw water was very low under normal conditions.After 10⁶ fold concentration of raw water,the genome of the virus was obtained for sequencing and analysis.The virus diversity in the raw water was complex,including ssDNA virus,dsDNA virus,linear DNA virus,linear RNA virus,circular RNA virus,etc.,defined by three viral species?Caudovirales,Herpesvirales,Ligamenvirales?,including human viruses?Spumavirus,etc.?,animal viruses?Asfarviridae,etc.?,plant virus?Eragrovirus,etc.?and phage?T₄ like virus,etc.?The virus with higher abundance in the raw water belonged to Microvirus,accounting for 18.16%.In the study,the volume of raw water samples was increased,but no viral genome was obtained for research,it showed that the virus can be well removed by conventional and O₃-BAC water treatment processes.The study used biodiversity sequencing and macro-gene sequencing to analyze the effects of carbon filtration units on microbial communities.The common pathogenic bacteria and conditional pathogenic bacteria in the effluent of carbon filter unit mainly come from the influent of this unit.The effect of carbon filtration on common pathogenic bacteria and conditional pathogens was not obvious.It brought uncertainty to the analysis of possible pathogens and conditional pathogens in the effluent of carbon filter unit.At the beginning of the end of backwashing of carbon filter,the abundance of pathogenic bacteria and conditional pathogenic bacteria in the effluent of carbon filter unit increased,and the burden of disinfection increased.Macro-genome sequencing showed there were not only bacteria,archaea,fungi and viruses,but also some protozoa and echinoderms on bio-active carbon.It had the genes which can degrade organic matter,cause human diseases and metabolize harmful substances to human body.The study established a rapid high-throughput detection method for 19common pathogens?B.cenocepacia,Staphylococcus aureus,etc.?A post-step regression analysis was used to establish a disinfection model for common pathogens?S.aureus?.The artificial neural network was used to establish a2-Methylisoborneol prediction model in water.It laid the foundation for the adjustment of disinfection process and the prediction of biological metabolites when pathogenic bacteria broken out.In this paper,the study on microbial safety of common water purification processes,conventional and O₃-BAC advanced water treatment processes were more in-depth.Relevant research results have positive significance for guaranteeing the biological safety of drinking water.