Research On Iron Release Of Water Supply Network Based On Dynamic Simulation Experiment And Multi-component Water Quality Model

In the urban water supply system,the water transmission and distribution link of the pipe network directly affects the water quality at the user end.Cast iron pipes are the most widely used pipes in the water transmission and distribution network,and the corrosion of the pipe walls will cause the p Henomenon of"yellow water"and cause abnormal water quality in the tap.Therefore,how to suppress the release of iron has become a research hotspot,but the current research on measures to control the release of iron has not proposed effective measures for the water quality in southern China.Based on the monitoring data of a water supply network in one city in the south,this paper aims to explore effective measures to suppress the release of iron from the water supply network.First,the characteristics of changes in the release of iron from the water supply network was analyzed using statistical methods,and the influences of other indicators that affect the release of iron was identified.Then,the dynamic simulation experiment was set up to analyze the influence of environmental factors,such as p H,alkalinity and corrosion inhibitors on the release of iron.Finally,the multi-component water quality simulation model was established based on the experimental data,and the model was used to further study the law of iron release in the pipe network.Based on the monitoring data of water supply network in a city in southern China,the water quality compliance rate,comprehensive index evaluation method,principal component analysis method and correlation analysis method were used to analyze the water quality status and the mutual influence law among the indicators.Results showed that the pipe water in 98%of the four districts have reached the water quality standard,and the water quality index of the pipeline network in most areas was basically within the range of 0 to 0.5,which indicated that the water quality of the pipe network was good and safe to drink.According to the correlation analysis between iron and other indicators,it can be concluded that there is a significant negative correlation between iron and p H,total hardness,free chlorine and total chlorine,and a significant positive correlation between iron and turbidity.Based on the analysis of the water quality characteristics of the pipe network,research on effective measures to restrain the release of iron from the water supply pipe network is carried out.Taking the unlined cast iron pipe as the experimental object,an innovative water supply network dynamic simulation experiment was set up to simulate the real water supply network environment.The structural composition and microscopic morp Hology of corrosive substances in the initial corrosion process were studied,and the influence of factors such as p H,alkalinity and corrosion inhibitors on the release of iron was analyzed.The experimental results showed that:（1）In the p H range of 6.5-8.5,the total iron release first decreased and then increased,the total iron release was the smallest at p H 7.8.（2）Increasing the alkalinity has a significant effect on restraining the release of iron from the water supply network.With the increase of alkalinity,the total iron release in the pipe network gradually decreased.（3）The addition of orthop Hosp Hate corrosion inhibitor did not inhibit iron release in the water supply pipe network;while after the addition of the polyp Hosp Hate corrosion inhibitor,it chelated with Fe²⁺on the pipe wall,which promoted the release of iron.Finally,in order to further clarify the inhibition effect of different p H,basicity conditions and pipe network operating time on iron release,a multi-component water quality simulation model of the pipe network was established,and the model was calibrated based on the aforementioned experimental data,so that the model could accurately simulate the change of total iron release with environmental conditions.Results showed that with the increase of network operation time,the concentration of iron increased gradually,but the release rate of iron gradually decreased.This was because with the reaction in the pipe network,the dissolved oxygen in the cast iron pipe was consumed,which made the iron release reaction stable.When p H varied in the range of 6-8.5,the concentration of Fe³⁺was larger than that of Fe²⁺,and iron release mainly existed in the form of Fe³⁺.