Research On Modeling And Control And Operation Optimization Of Water Treatment System For Urban Water Supply

City water supply as a city infrastructure，the water quality of water treatment system isclosely related to the people’s health.As the primary part of the water treatment process, thecoagulation result of water will influence the subsequent processing units，filtration as afollow-up treatment process，it determines the quality and the cost of water.Therefore, toensure water quality and safety while minimizing energy consumption,modeling, control andoperation optimization of the water treatment system in-depth study is very meaningfulresearch.with the support of the relevant research projects and the cooperation of the relevantwaterworks,the study on water treatment system includes4aspects, and the main contentsand research achievements are as follows:1. Study the modeling of the dosage in the coagulation process, and establish three differentstructural mathematical models.Aiming at the arbitrariness of dosage usage in current water treatment process, thereduced exponential model of coagulation dosage has been established based on existingresearch achievement and the realtime data, the parameters of the exponential model havebeen identified by using an improved differential evolution algorithm. Depending on thescope of raw water turbidity, the piecewise linear model has been established, which includesthree input parameters:the raw water turbidity, raw water flow and the pending filter turbidity,the former two as feed-forward variable adjustment and the latter one as feedback variableadjustment.the parameters of the piecewise linear model have been identified by using linearregression analysis. Finally using neural network technology to model, a neural networkblack model with the best performance has been given by comparing and analysingperformance of model,which is composed of different intermediate nodes and mappingfunctions. The model test results show that the models are accurate and instructive, accordingto the model to achieve accurate control of dosage, reduce blindness in the production processand ensure the stability of water quality.2. Analysis the control algorithms of the coagulation process in-depth and study severalcontrol algorithms and analysis their simulation results. Aiming at the difficulty to obtain the model of coagulation process, two improved PIDalgorithm have been introuuced:the PID controller based on improved differentialevolution(MDE-PID) and the two freedom degrees PID based on iterative feedback(IFT-PID).MDE-PID algorithm uses an improved mutation strategy that the target vector depends on thebest vector according to their fitness value, the simulation results show that the algorithm canimprove the convergence speed and accuracy. for the IFT-PID algorithm, the effects of theiterative step and the parameters’ initial value on the iterative process have been discussedand the iterative step has been improved,the simulation results show that the method is betterthan other traditional methods.Taking into consideration more disturbance and large delay,two new algorithms have been proposed: dual controllers scheme based on Smith modelcontrol and internal model control based on iterative feedback tuning(IFT-IMC). The dualcontrollers scheme combines the advantage of the traditional Smith predictor and theindependence of dual controllers,and compensate the tracking PI controller. the simulationresults show that the adaptation to object parameters change and the stability are better.IFT-IMC algorithm combines the strong robustness of internal model control and the strongadaptivity of IFT, it has good adaptability and robustness and the control performance is bestamong IMC-PID and Smith-PID, so it can be used to control this system to achieve effectivecontrol.3. Study on the change of the headloss and sludge content per unit volume during filtrationprocess from the experimental point of view and establish two kind of mathematical modelsfor filter.Aiming at the difficulty to obtain the headloss and sludge content per unit volume duringfiltration process, the mathematical models of head loss and sludge content per unit volumehave been established. Firstly, the headloss values of different filter depth have been obtainedby means of experiment data, the exponential relationship of headloss with the filterlayer depth change and the quantitative relation between the headloss and sludge content aregiven, so the sludge content of different layer depth has been calculated. Then with the helpof the relations and the existing research results,the relationship of the headloss with thevarious influencing factors and the relationship of the sludge content with thevarious influencing factors have been obtained. Finally, based on the data of headloss and sludge content, adopted modified differential method to identify the parameters,the model ofheadloss and sludge content are established and the model test results shows that the twomodels are accurate respectively. With the help of two kind of models, from themacro perspective of headloss and the micro perspective of sludge content, the cloggedsituation of the filter layer is clear and the filter cycle has been set more reasonabley.4. Establish the turbidity mathematical model of water pending treatment and study onoptimization experiment of filter filtration and backwash.From the perspective of the total energy consumption, the energy consumption equationof coagulation and filtration has been made,so the optimal turbidity expression has beenobtained when the total energy consumption is minimal. Based on the filter parameters andreal-time data, the expression parameters has been identified by using recursive identificationmethod.this research result proves the existence of optimal economic turbidity concept thathas been proposed qualitatively.Then the actual work situation of water plant has beenanalyzed and the optimization experimental study on the filtration cycle and backwashingtime has been implemented,lastly comparison of energy consumption between before andafter optimization has been discussed, The experimental results show that optimizing theexisting filter conditions appropriatly can reduce energy consumption significantly andsave the cost of water, which has good economic benefit and social benefit.Finally, the research achievements of this paper have been concluded and the future ofdevelopment of modeling,control method and joint optimal operation has been introduced.