Research On Key Technology Of Ammonia Nitrogen Field In-situ Online Monitoring System

Under the support of the field water quality in situ monitoring system of the cooperative project of Jilin Jiaheng Geological Environment Surveying and Mapping Co.,Ltd.,a prototype of the ammonia nitrogen online monitoring system was developed based on the real-time online monitoring requirements of ammonia nitrogen,an important water pollution indicator,in natural waters.In order to meet the requirements of anti-interference ability and measurement accuracy of the monitoring system in the open environment,this paper focuses on the study of ammonia nitrogen detection method and sensor anti-interference technology,which lays a theoretical foundation for the establishment of real-time and efficient water quality ammonia nitrogen monitoring system.Ammonia nitrogen in water quality is one of the important monitoring indexes for water pollution prevention and control.Excessive ammonia nitrogen in water will cause the death of fish and shrimp,the proliferation of algae and thus destroy the balance of aquatic ecosystem.In order to realize the remote,accurate and fast real-time online monitoring of ammonia nitrogen in the field waters,a set of chemical-free ammonia nitrogen online detection system based on ammonium ion selective electrode was developed in this project.In view of the problem that electricity is easily disturbed by environmental factors,support vector regression algorithm is introduced into the optimization of detection algorithm to realize the optimization and improvement of ammonia nitrogen monitoring method,which improves the anti-interference ability and accuracy of the system in the field open water detection.The research results of this paper are mainly composed of the following aspects:1)Selection of ammonia nitrogen detection method.The principle,advantages and disadvantages and application scenarios of various existing ammonia nitrogen measurement methods are analyzed.Combined with the research objective of this topic and the actual use requirements,the ammonium ion selective electrode method is proposed as the systematic ammonia nitrogen measurement method,and the performance parameters and detection process of the electrode are analyzed and verified.2)Research on some key technologies of the on-line monitoring system of ammonia nitrogen.Aiming at the problem that ammonia nitrogen detection in the field environment is easily interfered by environmental factors,resulting in inaccurate detection results,interference experiments were designed to analyze the main interference factors affecting ammonia nitrogen detection in the field environment.The support vector regression(SVM)algorithm was applied to the anti-interference detection of electrodes because of the coupling between the influence factors and the nonlinear effect on the results.Aiming at the problem that the input parameters of the algorithm are difficult to obtain,the particle swarm optimization algorithm is used to optimize the input parameters of the support vector regression machine,which improves the scientificity of the algorithm and the accuracy of modeling.The experimental results show that the determination coefficient of the antiinterference detection model of ammonia nitrogen established by this algorithm is 0.998,the average error of the test set is 1.88%,and the error is basically concentrated within 4%,which meets the requirements of national standard,and has good anti-interference detection ability and high accuracy and stability.3)Hardware circuit design and overall mechanical structure design of the on-line monitoring system of ammonia nitrogen.STM32F407ZGT6 is selected as the main control MUC to design the hardware control circuit of the system.USR-G780 4G LTE DTU is used to send and receive system data through GPRS communication technology,and RS485 bus is used to connect and communicate with DTU inside the system.The mechanical structure of the system is designed,which is divided into energy supply module,floating body and instrument bin according to its functions.The total power consumption of the system is calculated,and the energy supply module of the system is designed based on solar photovoltaic power generation.4)Test the overall performance of the system.The stability and accuracy of the system are compared with the actual water samples.The experimental results show that the system has high detection accuracy and good consistency with the national standard method,which can meet the requirements of real-time online monitoring of ammonia nitrogen in the field environment.