Research On AVRC Model Of Residual Chlorine Decay Based On Water Quality Assurance Of Pipe Network

Nowadays,chlorine disinfection is the most widely used method of drinking water disinfection in waterworks.And the disinfection by-products generated by chlorine disinfection is also too much.Therefore,the residual chlorine level in the pipe network is usually predicted and controlled by studying the chlorine decay model.The chlorine decay models include chlorine bulk decay models and chlorine wall decay models.The accuracy of the former is the basis for the latter modelling.In chlorine bulk decay models,first order model is the most widely used model,but it is not reliable enough.Moreover,other models are hard to apply due to some limitations.Among these models,VRC model has the advantages of high accuracy and good reliability,but there are also some points of it that have been questioned by other researchers.Therefore,the VRC model was improved and improved in order to improve its applicability.Inspired by the mathematical derivation of the VRC model,a second order model was developed through analyzing the influence factors of residual chlorine decay that can describe the reaction between chlorine and reactants in the bulk water,which was called the AVRC model.In this model,the overall reaction rate coefficient changed continuously in the reaction process,and its rate of change could reflect the gradual decrease in the reactivity of substances reacting with chlorine in the bulk water.The relationship between the reaction rate coefficient and temperature was represented by the Arrhenius relation.According to the model,chlorine decay experiments with different temperatures,secondary chlorination,and water mixing were designed and carried out.The model was solved and validated with experimental data.R²,RMSE and F-test of the model fitting was analyzed and the results show that the AVRC model has good accuracy and applicability.The improvements of the AVRC model over VRC could be summarized as follows:the maximum chlorine demand of the water sample is used to represent the concentration of all chlorine-reactive sites instead of the fixed value found through calculation.The change of the overall reaction rate coefficient can be explained by the conversion fraction of chlorine decay ratio rather than simply represented by a mathematical formula.The number of model parameters are reduced from four to two,simplifying the model and improving the efficiency of its calculation.The nonlinear least squares method function was used in the parameter checking process.Compared to the SCE method of VRC model,the calibration process is much simpler.The real initial chlorine concentration is applied in the AVRC model,instead of lower concentration after an initial loss period to improve the fit to data.In the range of initial chlorine concentration from 1.77 to 2.93 mg·L^-1,the model parameter value remained unchanged for HRB water samples.In 2²8?temperature range,the model coefficients at different temperatures can be calculated directly from the formula,without having to check the parameters at each temperature separately.For water mixing,the parameters can be used without change.In other words,the model coefficients can be directly derived from the model formula.