Design Of Real-time Online Detection System For Water Quality Parameters Based On Ultraviolet-visible Spectrum Absorption Technology

With the continuous development of society and economy,water pollution has become increasingly serious.After a large amount of domestic sewage is discharged into the water body,the p H,dissolved oxygen(Chemical Oxygen Demand,COD)and turbidity and other water quality parameters of the water body will change,water resources will deteriorate,and the ecological balance will be destroyed.Therefore,the rapid and accurate detection of water quality becomes very important.There are various water quality detection methods,but traditional water quality detection methods have disadvantages such as high cost,long detection cycle,complicated operation,susceptibility to interference,pollution,and inability to perform real-time detection.Aiming at the problems of traditional water quality detection methods,this paper chooses ultraviolet-visible spectroscopy as the design method of water quality detection system.Although UV-Vis spectroscopy overcomes the shortcomings of traditional water quality detection methods,environmental factors will interfere with the UV-Vis spectroscopy measurement during actual use.Therefore,it is necessary to analyze the influence of its interference factors on the water quality measurement results.Based on the ultraviolet-visible spectroscopy technology,this paper designs an online water quality detection system for measuring water turbidity and COD parameters.The water quality detection system mainly includes light source,spectrometer,photoelectric detector,AD acquisition module and FPGA transmission system.The system uses FPGA as the main controller to establish the concentration-voltage mathematical model of the water quality parameters collected by the AD9226 chip on the transmitted light intensity data,and uses the spectral data collected by the spectrometer as the standard to verify the accuracy of the established model.Finally,the prediction accuracy of different models is compared.At the same time,considering the environmental interference factors that may appear in the actual water body detection,the influence of turbidity,p H and temperature on the COD measurement results is analyzed,and the constructed model is compensated and corrected,and unknown water samples are detected.Compared with traditional water quality detection technology,this system provides a fast and high-precision solution for real-time on-line detection of on-site water sample water quality.This article mainly includes the following three aspects:(1)Aiming at the problems of long measurement period,complicated operation and inability to perform real-time detection of traditional water quality detection technology,a water quality online detection system based on ultraviolet-visible spectrum was designed,including the design of light path and circuit.The optical path consists of a light source,a cuvette and a spectrometer.The circuit mainly includes AD data acquisition and FPGA transmission system to realize the functions of transmitted light intensity data acquisition and voltage signal real-time display.(2)Based on the spectrum and voltage data measured by the water quality detection system,normalized spectrum analysis was performed on the spectrum and voltage data of the turbidity solution,and the PLS algorithm model and voltage solution model were established.The characteristic wavelength model,PLS algorithm model and voltage solution model are established using the spectrum and voltage data of COD solution.The turbidity and COD values were predicted using the established mathematical model,and the errors of the predicted values were compared and analyzed.(3)Taking into account the environmental interference factors that may appear in the actual water body detection,the influence of turbidity and temperature on the COD measurement results is analyzed,and the constructed model is compensated and corrected.Finally,unknown water samples are tested.