Evaluation And Study On The Disinfection Effect Of Liquid Chlorine And Sodium Hypochlorite Disinfectant In Water Supply Network

Liquid chlorine is more likely to leak and explode than sodium hypochlorite disinfectant.Both have a strong killing effect on bacteria,which can effectively ensure the safety of drinking water microorganisms.However,when the water from the water purification plant is transported to users through a complex water supply network,the residual chlorine continues to decay,and the water quality may deteriorate.Bacteria in the network will grow and reproduce again.Affect the water quality of pipeline network and user safety.Therefore,this paper combines the laboratory simulation pipe network system and the beaker test with the actual measurement of the water supply area pipe network before and after the replacement of liquid chlorine with sodium hypochlorite in the fifth water plant of Yangzhou City,to explore the residual chlorine attenuation and pipe wall of the pipe network disinfection Influence of biofilm growth and corrosion of pipe wall and water quality of pipe network.(1)The rule and influencing factors of residual chlorine attenuation in the pipe network water under the action of two disinfectants were studied through a laboratory-made pipe network simulation device.The results show that the decay rate of residual chlorine in the pipe network increases with the decrease of the initial residual chlorine;the decay rate of residual chlorine in the pipe network is positively correlated with temperature;the decay rate of residual chlorine in the pipe network is negatively correlated with pH value.Under the same influencing factors,the residual chlorine decay rate of sodium hypochlorite disinfection is slightly lower than that of liquid chlorine disinfection.(2)Through the simulation of the pipe network system,the growth law of the biofilm on the wall of the pipe under the action of two disinfectants was studied.The results show that the biofilms of cast iron and PE pipes can develop stably within 10 days,the biofilms of the former is 12.63?14.22 times of the latter.The amount of biofilm on the wall of cast iron is positively correlated with the concentration of residual chlorine,and the amount of film on the wall of PE pipe is negatively correlated with the concentration of residual chlorine.The corrosion rate of the cast iron pipe wall decreases with time and gradually stabilizes after 28 days.The higher the concentration of residual chlorine,the more severe the corrosion of the cast iron pipe wall.The corrosion rate of residual chlorine is 0.5 mg/L,1.5 mg/L and 3.0 mg/L between 0.54?0.006 g/(m2·h).The aging rate of PE pipes increases with time,and the aging rate is between 0.003?0.025 g/(m2·h).(3)Through the actual measurement of the factory water and the water supply pipe network of the fifth water plant from June to December,the comparative analysis of the changes in the water quality of the pipe network after treatment with the two disinfectants and the relationship between some water quality indicators and temperature.At the same time,supplemented by a small laboratory beaker test,the relationship between different forms of aluminum content in water and pH was explored.The results show that the residual chlorine decay exponentially along the way.The residual chlorine decay of sodium hypochlorite is slower than that of liquid chlorine,which is more conducive to maintaining the residual chlorine in the pipe network.During the sodium hypochlorite disinfection,the pH value of the pipe network is higher than that of liquid chlorine disinfection.During the liquid chlorine disinfection,the pH value of the pipe network increases from 7.48 to 7.8 along the pipeline During the sodium hypochlorite disinfection,the pH value of the pipe network decreases from 8.0 to 7.4 to 7.6 along the pipeline.There was no obvious change along the pipeline network CODMn.Sodium hypochlorite disinfection effluent CODMn is slightly lower than that of liquid chlorine disinfection.The turbidity of the pipe network increases along the way.There was no significant difference in the turbidity of the two disinfectants.The total number of bacteria in the pipe network water increases along the index.The total number of bacteria in liquid chlorine disinfection is slightly higher than that of sodium hypochlorite.CODMn is negatively correlated with temperature;turbidity and total bacterial count are positively correlated with temperature.The AOX content of the pipe network increased linearly along the way,and sodium hypochlorite disinfection reduced the AOX by 19.8%compared with liquid chlorine disinfection.During sodium hypochlorite disinfection,the chlorate content of the pipe network increases linearly with time,and the growth rate constant is 0.0002 mg/(L·min).Liquid chlorine disinfection basically does not produce chlorate.The difference in total aluminum concentration along the pipe network is not large,between 244.38?308.71 ?g/L.During liquid chlorine disinfection,the dissolved aluminum content increased along the route;during sodium hypochlorite disinfection,the pipe network dissolved aluminum content decreased along the route.The average soluble aluminum content increased by 6.7%compared with liquid chlorine disinfection.In the range of pH=7.4?8.2,the content of dissolved aluminum increases with the increase of pH.