Research On Microbial Growth Model And Character Istic In Water Distribution System

Water quality safety is an important part of water supply system which is large,complex,and whose operation condition is transiently change.In order to guarantee people's health,the water quality safety is no longer just staying in the monitoring of the water works but paying more attention to the water pipe network peripheral.However,the number of water quality monitoring stations in water supply network is limited.If we want to get a comprehensive water quality in water distribution system in the whole space and time distribution,we should build up a water quality model for the water supply system,and the water quality simulation is necessary and reliable way.Based on the analysis of existing microbial growth models,these models didn't consider speed changes effect and diffusion effect in the water distribution system.Designing experiments to verify the speed effect,buliting microbial growth model,adding speed model and diffusion factors.Because wall zone is stationary and bulk flow is moving,those meshes are divided to static and dynamic meshing respectively,and we proposed the EulerianLagrangian split method to calculate its numerical solution,and the microbial growth model coupled unsteady hydraulic conditions undergoing changes water supply to simulate its growth.In this paper,the main work and achievements are as follows:(1)Experiment research with speed change effecting on microbial growth.The current microbial growth models did not take into account in speed effect on water quality,and the experiment found that speed changes had a significant effect on microbial growth.Through studying on the microorganism concentration with the experiments,we can obtain distribution of residual chlorine concentration and AOC concentration change and the biofilm growth.The results showed that speed effect has a significant effect on microbial growth.This research can provide basis for the construction of microbial growth model.(2)According to the analysis of microbial growth mechanism,this chapter constructs the microbial growth model which contains consume organic matter,natural death,melting,deposition,disinfection and the microbial inactivation in the process of microbial growth.This paper proposes two main innovations of the model,the first is the accumulation of biofilm formed on the model,the accumulation of microbial membrane and accumulation of organic matter and the second is to consider the shear force impact on the biofilm formation.The parameter estimation of microorganism growth model was estimated by Bayes parameter estimation,and the optimization parameters were obtained.The growth characteristics and biofilm accumulation process of microorganism in pipeline network were obtained by simulation of single-tube and tube network.(3)In the classical water quality model,axial dispersion is generally ignored during simulation in WDS.In this study,the classical model is embedded in axial dispersion and applied to numerically simulate the hypothetical contaminant-intrusion from water source under hydraulic unsteady conditions.The ELOS model is used to solve the advectiondispersion-reaction equations and compared with the analytical solutions and other numerical solutions.When u is big,the dispersion effect can almost be neglected.However,when u is small,the dispersion effect begins to become prominent.The contaminant concentration at downstream node is gradually accumulated with time along the upstream pipelines from the source,which is particularly reflected in the terminal.The simulation results compared with EPAnet-MSX show that biomass concentration may exhibit synthetic effects of axial dispersion and radial mass transfer and reaction given the multicomponent reaction transport processes.The dispersion effect features a large difference between the bulk flow and wall zone to mutually increase the radial mass transfer and reaction.Therefore,biomass concentration significantly changes,and this phenomenon is particularly reflected in the low flow velocity.(4)Water quality prediction research under the variance of water supply: water supply prediction,water hydraulic parameters on the change of the calculation and water quality prediction.In this paper,a multiple random forests model,integrated wavelet transforms and random forests regression(W-RFR),is proposed for the prediction of daily urban water consumption.The results indicated that the W-RFR can capture the basic dynamics of the daily urban water consumption.The forecasted performance of the proposed approach was also compared with those of models,i.e.,the RFR and forward feed neural network(FFNN)models.The results indicated that among the models,the precision of the predictions of the proposed model was greater,which is attributed to good feature extractions from the multi-scale perspective and favorable feature learning performance using the decision trees.After rebuilding the hydraulic model,each section node parameters such as traffic flow and pressure are calculated.In order to increase the randomness of the water consumption per user,we embedded the normal distribution of random numbers into water hydralic models,and then the new hydraulic parameters are calculated and predicted water quality.Through the 219 days of water quality simulation we can get in: the components were added to the interaction,the hydraulic change effect was obvious,the microbes were influenced by all kinds of the most obvious,AOC concentration change was minimum,residual chlorine concentration was in the middle,wall area biofilm is the accumulated,it is still affected by the environment latterly.(5)Build online analysis platform of water quality and hydraulic based on the GUI in Matlab.This chapter will set up visual graphical user interface based on the analysis platform in the urban water supply network coupled with water quality and hydraulic model related to 2th,3th,4th,and 5th chapters.The construction of the platform will provide a highly efficient management for urban water resources development and utilization.Users do not need to master the principles of the model,nor do they need to be good at computer technology to achieve water quality assessment analysis.It provides solid technical support for the analysis of water quality model in the urban water supply pipe network.