Characteristics Of Bacterial Proliferation Induced By Stagnation In Indoor Drinking Water Pipelines

Drinking water safety is closely associated with human health.Because drinking water is directly exposed to the external environment where bacteria are abundant,the breeding of bacteria in drinking water is inevitable.In order to create a hygienic environment of drinking water supply,major water plants will choose drinking water sources,the address of the water plant and the water treatment process strictly to ensure that the effluent indicators meet the national drinking water standards.However,after long-distance transportation,when drinking water is transported from the water plant to thousands of households,the number of microorganisms and population structure will undergo subtle changes.Due to the limitations of technology and personal privacy,it is difficult to monitor the microbiological indicators of indoor drinking water.Furthermore,due to the inevitable natural laws,stagnation will take place to some extent.It has a major social value and scientific significance to explore the changes in water quality,microbial proliferation characteristics and bacterial community structure changes in indoor drinking water pipelines in the state of stagnation.This study takes indoor tap water as the research object,mainly studies the inevitable overnight stagnation caused by natural causes to induce bacterial proliferation characteristics of indoor drinking water pipelines,diagnoses the seasonal phase succession law of microorganisms in the water body of indoor drinking water pipelines.Exploring the coupling mechanism between pipeline water quality,microbial change characteristics and sudden algal pollution and water environmental factors,with a view to providing theoretical support for improving the research of microbial ecological structure in municipal pipelines and providing a scientific basis for improving the health status of drinking water.The main conclusions of this study include:?1?Revealing the characteristics of seasonal succession induced by overnight stagnation to the microbiological status of indoor drinking water pipes.The analysis of chemical parameters of water quality showed that the indoor water retained overnight in the water pipe showed regular changes with the seasonal changes,and the bacterial proliferation characteristics changed significantly with the seasonality.The proliferation in the high temperature period in summer and autumn was 3.31 time.ATP analysis and Biolog fingerprint metabolic technology analysis showed that the correlation analysis of carbon source metabolic characteristics showed that the fresh water body of the direct water supply was drastically affected by the season.The bacterial concentration in the overnight stagnation water reached the highest in summer,and the total ATP content in the water increased 4.20,5.15,5.22 and 2.32 time after stagnation,respectively.The metabolic activity of microorganisms in the secondary water supply is significantly higher than that in direct water supply.Co-occurance network analysis shows that Nitrospira,Dongia,Bryobacter,Halomonas,Corynebacterium play a leading role in the structure of the stagnation water network,while the core genus of fresh water was Hyphomicrobium,Pseudorhodobacter,Nesterenkonia,Psedomonas,Ralstonia,etc.?2?The quality of overnight stagnant water deteriorates,and both iron?Fe?and residual chlorine are below the Chinese drinking water standard?GB 5749-2006?on the influence of artificial heating.Bacterial concentrations,ATP contents,and bacterial metabolic capacity in water increased significantly after overnight stagnation?P<0.001?,the microbial community structure was more diverse and abundance,the content of opportunistic pathogens increased significantly and Legionella had become one of the hub genus bacteria,indicating that the water after stagnation had potential threat to human health.Temperature and sulfate have a significant effect on the formation of bacterial population structure.The combination of flow cytometry?FCM?,Biolog,ATP and DNA sequencing provides stability for drinking water bacterial detection a comprehensive approach.?3?During the natural warming period in summer,the increase in Fe concentration in August was the largest?6.04 time?;the TOC concentration was maintained at 1.31 mg/L?2.51 mg/L,and gradually increased.In August,the bacterial growth factor was the largest,reaching 2.33 times;the total ATP concentration showed a significant positive correlation with the total bacterial concentration?R²=0.83,P<0.01?,and the intracellular ATP ranged from 0.17 to 12.94×10^-17 g ATP/mL.The cell concentration also increased significantly after overnight of detention.Studies have shown that the higher the temperature,the worse the water quality after drinking water after overnight stagnation.?4?Drinking water quality had deteriorated,and the bacterial population interaction had changed significantly on the impact of low-concentration algae organic matter?AOM??TOC=5.77±0.01 mg/L?.In the later period of detention of drinking water,denitrification predominates,resulting in a significant increase in NO₂^--N content.The composition of organic matter in the water changes after stagnation,from fulvic acid-like,protein-like,and humus-like to humus-like.Under the stimulation of these organics,the number of bacteria and ATP content increased significantly,and the total cell concentration of bacteria reached 57.90±4.86×10⁵ cells/m L during the retention process.AOM is an important factor that affects the bacterial community structure.?5?Nitrogen and phosphorus indicators in the water all exceed the national standard?GB 5749-2006?under the stimulation of high concentration AOM?TOC=7.14±0.15mg/L?.Complicated,from humus to protein-like and fulvic acid-like,the bacterial concentration increased 28.08 time during stagnation,the microbial diversity in the water decreased.Proteobacteria,Bacteroidetes,Mycophyta,Planctomycetes is the dominant phylum.Neosphingobium,Sphingomonas,Acidovorax,Alcaligenes plays an important role in community structure.