Research On Key Technology Of Multi Parameter Water Quality On-line Monitoring System Based On Spectral Analysis

Water resources are the material basis for the survival and development of human society.China is a country with a shortage of water resources,and the overall situation of water pollution is serious,which badly restricts the sustainable development of China's economy.Water quality on-line monitoring is an important technical method and scientific basis with impressing demand for us to master water environmental quality and implement water environment protection and control.On the basis of systematically analyzing the present situation of water quality on-line monitoring system at home and abroad,in order to meet the requirement of water quality on-line monitoring system such as speed,continuity,automation,low-cost and multi-parameter,the article studies the chemical pretreat and detect method using spectral analysis on the main water pollution indicators such as chemical oxygen demand?COD?,total phosphorus?TP?,ammonia nitrogen?AN?and sudden heavy metal water pollution indicator hexavalent chromium(Cr⁶⁺).We have proposed a new multi-parameter water quality on-line monitoring system?MWQMS?structure based on Flow-Batch Analysis?FBA?and continuous spectrum analysis technology,and the key technologies such as integrated light source and multi-function sample detection chamber,system sampling and cleaning,on-line chemical pretreatment,water quality detection information processing,intelligent control,system self-inspection and remote monitoring have been broken through.We have studied the characteristics,main constructive factors and solutions of multi-parameter water quality monitoring spectral signals and background interference,and have formed the theory and new method of spectral signal processing for multi-parameter water quality monitoring.The engineering prototype of MWQMS has been successfully developed and the key performance indicators testing of the prototype and the comparison test using actual water samples have been carried out.The experimental results show that the prototype meets the application requirements for multi-parameter water quality on-line monitoring.The main contents of this paper are as follows:?1?The research status and the existing scientific and technical problems of multi-parameter water quality on-line monitoring technology and equipment based on spectral analysis have been systematically and thoroughly studied.Aimed at the present problems of first generation prototype in the laboratory,the technical way for the MWQMS based on spectral analysis has been determined.?2?Pretreatment and determination methods of multi-parameter water quality on-line monitoring based on continuous spectrum analysis have been studied.The chemical pretreatment and the spectral determination methods of COD,TP,AN and Cr⁶⁺have been determined.?3?Aimed at the problems of the first generation prototype such as poor accuracy and repeatability and the functional requirements of water quality monitoring,a new prototype structure of MWQMS based on FBA and continuous spectral analysis technology has been proposed.The key technologies such as modual light source,multi-functional sample detection chamber,system flow path and cleaning,on-line chemical pretreatment,information processing of water quality monitoring,intelligent control,system self-inspection and remote monitoring have been broken through.The engineering prototype of MWQMS based on spectral analysis has been successfully developed.?4?Aimed at the characteristics of spectral singal and noise for water quality on-line monitoring,an adaptive spectral signal denoising method based on Ensemble Empirical Mode Decomposition?EEMD?has been proposed.On the basis of researching the invariance of dual-wavelength light intensity ratio to eliminate the systematic error of absorption spectroscopy,a new method for suppressing background interference with dual-wavelength spectroscopy based on the transmitted light intensity of measured water sample as the reference light intensity has been proposed.The accuracy and efficiency of the water quality monitoring system have been improved.?5?Based on the MWQMS developed in this paper,the on-line chemical pretreatment control conditions and determination process of COD,TP,AN and Cr⁶⁺have been experimental researched.The key performance indicators testing of the MWQMS and the comparison test using actual water samples have been completed.The results show that the MWQMS developed in this paper meet the requirements of national environmental protection standards and the application requirements of multi-parameter water quality on-line monitoring.