Optimal Operation Of Multi-source Water Supply System And Iron Release In Water Supply Network

Realizing the optimal operation of water supply system, inhibiting iron release iniron pipes, preventing iron concentration in water supply network out of limits andensuring the water supply safety are the common problems of water supply enterprises.The main objectives of this dissertation are as follows: the optimal operation model ofmulti-source water supply system and its solving method. Aimed at the complexity ofthe water supply system optimization scheduling model and the shortage of theexisting algorithm, the more suitable algorithm is studied. The phenomenon of ironrelease in water supply network caused by water quality index and the hydraulicconditions change was examined. Based on the analysis of the morphology andcomposition of pipe scale and the iron in the water, the single factor rotationexperiment was used to determine the impact of different water quality indexes andhydraulic conditions change on iron release. Surround the iron release rules under thecondition of water source switch and multi-water resources supply, the control effect ofadjust the pH value and alkalinity, addition the polyphosphate inhibitor was studiedrespectively. The results are shown below:First, the hydraulic balance equations are replaced by BP neural network model ofpipe networks, and then a more universally applicable water supply systemoptimization scheduling model is established. The improved particle optimizationalgorithm is used to solve the model, which can avoid the algorithm getting into a localoptimum, and improve the precision of the algorithm. Then, the model was applied toTianjin water supply system, which proved the applicability of the model and thefeasibility of the algorithm. Second, the morphology and composition of pipe scale in different pipes all haveobvious layered structure: compact appearance and internal loose. The iron oxides arethe primary components, account for more than70%of the total. Due to the differentdiameter, pipe laying years, water hydraulic and water quality conditions, themorphology and composition of the pipe scale have some differences. The iron in thebulk water is comprised of different iron oxides which suspend in water with tinyparticles, and it is the direct cause of the "red water" phenomenon. On this basis, theprocess of iron release and "red water" formation are discussed, different iron releasemodels all think that the dissolution of high solubility ferrous compounds is the mostimportant process of iron release.Third, the inlet water quality including DO, pH, chloride ion, sulfate, alkalinityand residual chlorine, and the hydraulic state, such as flow rate, residence time, flowregime and flow direction change will affect the release of the iron, but the mechanismis not the same, the former often lasts longer, while the latter is a short-term effect.Then the grey correlation analysis method was used to analyze the correlation degreeof seven factors with iron release, and the sorting result for: Cl-> SO42-> alkalinity>residual chlorine> time> pH> velocity, which provides the basis for the iron releasepractical control.Fourth, the frequent switching between the different water resources will destroythe passivation layer on the surface of the pipe scale, the iron release rate will rapidlychanges, and then will be eased, but it requires a longer time to the formation of a newequilibrium. To the mixed water in dividing line, it is difficult to form the stablepassivation layer because of the water quality changes constantly, the continued highrate of iron release occurs. It can be suppressed only when the proportion of theYangtze River water is as high as75%or more.Fifth, the controlling technologies of adjust the pH value and alkalinity; additionthe polyphosphate inhibitor can decrease the iron release. Via the comprehensiveanalysis of different control techniques, increasing pH value of the product water is avery effective method.