| With the rapid development of China’s industrialization,the problem of environmental pollution has become increasingly prominent,and the problem of water pollution has caused widespread concern.Chemical oxygen demand(COD)is one of the important indicators issued by the state for water quality testing to measure the extent to which water is contaminated by organic matter.For the domestic COD detection device,the detection accuracy is not high enough,the injection method is not flexible enough,and the cost is high.This paper has carried out related research on the COD detection device.The main contents of this paper are as follows:(1)Aiming at the problem that the traditional COD detection device liquid intake metering system is not flexible enough,the continuity is poor,and the injection precision is not high enough,this paper proposes a new method of liquid sampling.The method takes the injection pump as the core,and the continuous,smooth,flexible and accurate measurement and addition of the water sample and the reagent can be realized under the cooperation of the eight-way valve,the pure water valve and the high pressure valve.(2)At present,the COD detecting device uses the photoelectric detecting mode of the single receiving end for the measurement of the COD value,which is the reason why the accuracy of the COD detection cannot be further improved.Based on this,this paper proposes a dual-receiver photoelectric detection method,which has higher detection accuracy and more accurate measurement of COD value.Conventional COD detection devices use a least squares method to establish a model between the photodetection signal and the COD value.In fact,the detection signal is not linearly related to the COD value,which makes the model established using the least squares method inaccurate.In order to further improve the accuracy of COD value detection,this paper designs a support vector regression(SVR)COD value model,which is more accurate for COD calculation.(3)Aiming at the problem of parameter setting,long adjustment time and poor adaptability of PID temperature control process in digestion reaction,this paper puts forward the theory of fuzzy control to PID temperature control process,and designs fuzzy PID temperature control model,which is more precise in temperature control,shorter in adjustment time and more adaptable.(4)According to the optimization of the key technologies of the detection device,the overall scheme of the COD detection device is established,the hardware platform of the detection device is built,and the software system is developed.Design experiments to verify the liquid metering scheme,photoelectric detection scheme and SVR model designed in this paper.(5)Based on the analysis of water environment characteristics and water quality prediction model,a water quality COD prediction model based on BP neural network was designed to predict the highest daily COD content in the next three days.In order to further improve the prediction accuracy of the model,the genetic algorithm(GA)is used to optimize the parameters of the BP neural network,and the GA-BP prediction model is established.The prediction results show that the GA-BP prediction model is more accurate than the BP prediction model and can be used to predict the highest daily average COD value in the next three days. |
