Research On Portable COD Detector Based On UV-Vis Spectroscopy Technology

Nowadays,the process of social development is becoming faster and faster.The degree of industrialization and urbanization in China is becoming higher and higher.Subsequently,the pollution of the water environment is becoming increasingly serious.Water quality detection can judge the degree of water pollution as early as possible,and provide early warning for the subsequent timely treatment of polluted water sources.Chemical oxygen demand(COD)is an important indicator for water quality detection.However,traditional COD detection methods have problems such as slow detection speed,high detection cost,poor portability,complex operation,and easy to generate secondary pollution.Aiming at the above problems,this paper designs a portable COD detection system based on the principle of UV-Vis spectroscopy technology.The COD detection system has the advantages of high detection accuracy,fast detection speed,no secondary pollution,and real-time detection.It can perform turbidity compensation while detecting COD,and is used for COD detection of surface water.The main research contents of this paper are as follows:1.A data processing algorithm for detecting COD based on UV-Vis spectroscopy technology is proposed.Combined with the principle of dual-wavelength absorption method to detect COD,the characteristic wavelengths of COD and turbidity detection are selected respectively by analyzing the absorption spectra of COD and turbidity.The COD prediction model is established.The DWA＿PLS algorithm is proposed for turbidity compensation when detecting COD with turbidity interference.The method of establishing turbidity compensation model is introduced in detail.2.A portable COD detection system based on UV-Vis spectroscopy technology was designed,including optical system,hardware system,and software system.The optical system includes two light sources,sample cells and a photoelectric sensor.The photoelectric sensor is used to convert optical signals into voltage signals.The hardware system includes ARM controller module,photoelectric signal acquisition circuit module,LED constant current source circuit module and power supply circuit module.In the circuit structure,the voltage signal output by the photoelectric sensor is processed by RC filter,and converted into digital signal after AD conversion for processing by the core controller.The software system includes sensor control and signal acquisition.The data is processed according to the established model,and the COD concentration value is calculated and displayed on the screen.3.The portable COD detector based on UV-Vis spectroscopy technology was analyzed experimentally.The stability of the light source of the COD detection system is tested.COD standard solution and turbidity standard solution were tested.The turbidity compensation model of COD detection system is established according to DWA＿PLS algorithm.Finally,the detection accuracy,average relative error and standard deviation(RSD)of the COD detection system are verified.