Study On Water Quality Analysis And Improving Program Of Water Distribution Network In N District

With the development of economic,and people living standard rise,safe and high quality water quality has increasingly become the focus of attention.In general,China's large and medium-sized city water plant annual factory water comprehensive pass rate of up to 99% or more.But residents complain of water quality issues are still frequent,the main reason is that a complex biological role and physical and chemical changes occurring in water,when the water is transported from the water plant to the user through the pipe network,water quality has changed.Therefore,the study of transmission and distribution technology to keep the water safe will become the focus of water quality assurance research.In this thesis,we track the changes of water quality when water is transported in the trunk pipeline network and the branch pipeline network.First,a hydraulic model is needed for the pipe network,based on the hydraulic model,selecting a single-stranded water line that is not affected by the mixing of water,setting the sampling point on the pipeline,according to the results of water age that calculated by the model,then sampling detection at the fixed time and place.According to the sampling results,in the long-term stable operation of the water supply network,the water quality indicators can meet the national standards,and maintained at a level below the national standard of 30%.In the sampling process,because of the network structure problem cause stagnant water points,and individual water quality indicators have changed to some extent while the pipe flow too fast or too slow,turbidity increased 218%(0.22NTU),CODMn increased 38%(0.32mg/L).The influence of pipe material on water quality is different,the chemical stability of the old concrete pipe is worse than the steel pipe and the ductile iron pipe.At night the residual chlorine content below 0.15mg/L in the end of branch pipe network,the water that back-end users used is unsafe.After that,we select four secondary water supply community th at different in construction age and water supply way,then we sampling in the tank that on the ground floor or the roof,and the faucet in the home.According to the sampling results,the water quality that supplied by variable frequency pump and pressure tank water supply or non-negative pressure water supply is better than traditional forms of water supply,turbidity keeping about 0.15 NTU,residual chlorine stay above 0.5mg/L.The concrete structure of the water tank design size is so large that water stay too long,the maximum stay time is 103 h that far more than the specifications required less than 48 hours,therefore,the water deteriorate and microbial indicators exceed the national standard.The water tank isn't cleaned more than half a year.In resident's home,there are some pipe that residents don't use frequently,the water in that pipes deteriorate.In order to solve the water quality problems caused by the structure of pipe network,Using the model proposed reform of the pipe network structure optimization comments,to reduce stagnant water points,avoid pipeline flow velocity too high or too low,increase the rate of pipe ring formation.In order to solve the water quality problems in the secondary water supply,the property should strengthen the maintenance and management of the secondary water supply facilities,Water Division should to strengthen supervision and inspection work,do a good job in monitoring records.Recommended new community with non-negative pressure water supply mode or variable frequency pump water supply mode,it can avoid the secondary pollution of water quality in the water tank.The calculation of water consumption by residents should not be too large,to avoid the volume of the water tank too large that the water stays too long.For the old community,it is recommended to modify the water tank,or cleaning the water tank mor e frequently,in order to protect the residents to safe water.