Study On Method Of The First Order Chlorine Decay Model Parameters Determination

With the progress of society, the demand for drinking water is no longer satisfied merely to "quantity", but more emphasis on "quality." As the network large and complex, regulation of water quality is inseparable from the water quality model, so the establishment of an accurate network model water quality is of great significance for water quality forecast, regulatory and emergency incidents. Currently,in the widely used quality simulation software EPANTE, there are two important factors that affect the accuracy of residual chlorine decay, they are the residual chlorine decay in the pipeline and mixing at the node. Therefore, the purpose of this study is to modify the way that determine the factors that have a significant impact on the accuracy of the model by experiment and numerical simulation, making the water quality model can more accurately simulate the actual water quality conditions in the pipe network.Firs, through the static experiments to study the main experimental factors that affect the bulk decay and wall decay of residual chlorine and the rule of residual chlorine decay and the changes of bacteria and BDOC in different conditions. It was found that: for the experiment in the beaker, the temperature has positive correlation with chlorine decay coefficient, and initial chlorine concentration and PH have negative correlation with chlorine decay coefficient; The measured chlorine decay data was analysed for three stages through exponentially fitted method, the correlation coefficient of each stage is very high, and have a large difference from each other, showed a trend of decrease gradually; For re-chlorination, chlorine concentration increases and chlorine decay rate is reduced. The measured chlorine decay data was analysed for two stages through exponentially fitted method, it is found that chlorine decay rate was slow at first and then quickly, which is different from chlorination. But the difference between two stages of residual chlorine decay coefficient is small; For the pipe study, it is found that initial chlorine concentration and the age of pipe have positive correlation with chlorine decay, PH and diameter of pipe have negative correlation with chlorine decay.Then, Implement a numerical simulation for the mixed water at the node in network by orthogonal experiment method. For the + junction, the ratio of diameter(Ds/Dw)and the ratio of inflow Reynolds(Res/Rew)have a great infect on the mixing of node. For the double –T junction, the distance between the double-T(H), the ratio of diameter(Ds/Dw)and the ratio of inflow Reynolds(Res/Rew)have a great impact on the mixing of node. Then, carry outing a comprehensive numerical simulation analysis for the independent variables which have a significant impact on the index of mixing at the node. By SPSS software, the experimental data and the mixing rule were subjected to regression analysis, and fitting to get two different node connection mode of mixed water quality equation.Combining with the northeast city water distribution system, based on the main water residual chlorine attenuation coefficient that was divided into three stages by water age and water quality model of mixing at node, some partial source of EPANET was improved. Compared the water quality simulation results with the actual value of the network, and analyzing the accuracy of the model.The results showed that theimproved program has higher accuracy.