Research On Online Monitoring System Of Ammonia Nitrogen In Water

In recent years,water pollution incidents occur frequently,and eutrophication has become the global concern.The content of ammonia nitrogen(NH3-N)in the water body is closely related to the eutrophication of the water body.The change of ammonia nitrogen content can objectively reflect the degree of water pollution.The principle methods of detecting the ammonia nitrogen,used for the automatic analysis,are ammonia-gas-sensing electrode method and Nessler's reagent colorimetric method.However,Nessler's reagent colorimetric method has many problems in the preparation of reagent,such as complex reagent preparation,highly toxic,long detection cycle and so on.Ammonia sensitive electrode rule is not affected by these factors,and the use of the market is expanding year by year.However,the ammonia sensitive electrode is affected by temperature,blank potential value and other factors.Therefore,in view of the above problems,based on the developed reagent freeon-line detection instrument for ammonia nitrogen,the instrument is optimized to further improve the detection accuracy,and reduce equipment maintenance rate.The main research results can be divided into four parts:1)Based on the traditional ammonia electrode method,the method to measure the ammonia nitrogen added needs to add sodium hydroxide reagent.it can lead to the problems of high running cost and easy cause corrosion.According to the characteristics of ammonia electrode by ion impact,this paper puts forward a scheme and implementation of an on-line monitoring device based on electrodialysis electrolysis of tap water instead of sodium hydroxide.Using PLC and touch screen control the operation of on-line monitoring system for ammonia nitrogen,which the upper computer implements data storage and management,as well as remote monitoring functions.And compared with GB method,the error is less than 7%,it meets the needs of online monitoring of water quality ammonia nitrogen.2)The detection process,hardware structure and system parameters are further studied.The influences of electrodialysis current,time,light,air and other factors in the detecting process are analyzed by experiments,and the best scheme of electrodialysis is obtained.Aiming at the problems in detecting process and cleaning process,the improved programmers are put forward,and the design scheme and working parameters of the instrument are optimized.Compared with the previous experiment,the detection cycle is shortened,and The service life has reached three months,and the detection accuracy has been increased from 7% to 5.5.3)Further research shows that the output potential of ammonia gas sensing electrode is affected by the concentration of ammonia nitrogen,temperature,pressure,blank potential value,stirring speed and other factors.The relationship between each factor and the output potential are analyzed.According to Nernst equation,the orthogonal test scheme is designed.This paper put forward the method of multiple regression analysis establishes a model to compensate the effects of the temperature,pressure,initial potential on the output potential of ammonia sensitive electrode,and the accuracy of the model is verified.The measurement errors of actual water samples are within 5%,and the stability and reproducibility of the data are improved.4)Based on the GPRS network and using LABWIEW software,the joint monitoring scheme of multi-ammonia nitrogen on-line monitoring device is established,which realizes the data transmission and remote control function of multiple ammonia nitrogen on-line detector.