Research On Influence Factors Of Iron Stability In Ductile Iron Pipe Under Water Source Switch

At present,there is an increasing shortage of high-quality freshwater resources on the surface.Water diversion projects and water source switching projects have been adopted by some cities.In the process of water source switching,it is necessary to focus on the iron stability of the pipe network.A region plans to introduce a new water source to supply water.This article analyzes the current status of regional water sources,which can provide a reference for the prevention focus after the implementation of water source switching in the future.This article makes a preliminary judgment on the iron stability of the pipe network from pipeline characteristics,differences in water between the two places and Larson index.Then the judgment was verified by plastic steel and ductile iron pipe section reactors.The influencing factors that easily increased the risk of pipe network iron stability were determined.The factors that increase the stability risk of pipe network are identified.This article also builds a ductile iron pipe circulation operation device to further simulate the water quality changes under real hydraulic conditions,and clarifies the influence of flow rate and direction on the changes of turbidity and total iron concentration.Subsequently,the effectiveness of increasing the pH to control turbidity and total iron release was verified.Provide feasible precautions to maintain the iron stability of pipe network after water source switch.The main results are:In the vicinity of the boundary between the two water sources,27%of the sampling points have a risk of exceeding the standard of iron ion,and 18%in the remaining areas.It is recommended to take preventive measures against changes in hydraulic conditions near the boundary with the hydraulic model.Analysis of the pipe section characteristics found that the ductile iron pipe scale is relatively loose,the main components are SiO2 and a small amount of ?-FeOOH.The Larson index of CA County's treated water is 0.39,which means it is less corrosive.Through the experiment of the pipe section reactor,it is found that the mixing ratio has no obvious effect on the iron stability of the pipe network after water source switching.Besides,turbidity and total iron release in the ductile iron pipe are easily affected by the change of the flow rate.Comparing the microscopic morphology of pipe scale before and after the experiment,it was found that iron stability of the pipe section after water source switching was mainly due to the shedding of particles caused by hydraulic erosion.Therefore,it is recommended that water plant flush the pipe network and replace the old pipes in time before water source switching.In the experiment of simulating the real hydraulic conditions in the ductile iron pipe circulation device.It is found that the residual chlorine attenuation coefficients of the new and the original factory water are 0.015 and 0.087min-1,respectively.After water source switching,the initial residual chlorine concentration of treated water should be adjusted to prevent problems such as excessive residual chlorine concentration.Quantitative analysis of changes in water turbidity and total iron concentration in ductile iron pipe under different flow rates,pH and directions.Quantitatively studied the effect of increasing the pH of inlet water on the turbidity and total iron release in ductile iron pipe.Provide emergency countermeasures to deal with the problem of excessive turbidity and iron release after water source switching.