For a long time, water quality monitoring usually uses manual water sampling, and monitoring and analysis in the laboratory not only consumes a lot of manpower and material resources, but also has a long working period. The automatic water quality monitoring system can keep abreast of water quality changes and improve work efficiency. It is widely used in water quality early warning systems, boundary river water quality management, supervision and management of sewage inflows, and monitoring of total pollutants in water functional areas.
Brief History: The construction of China's water quality automatic monitoring system started in 1988. In the same year, the first automatic water quality monitoring system was established in Tianjin. Since the 1990s, automatic water quality monitoring systems have been built in key sections of Shanghai, Beijing, Songhua River, Huaihe River, Yangtze River, Yellow River and Taihu Lake. Local water quality has been established more than 500 local level according to environmental management needs. Monitoring System. Since 2011, the pace of construction of automatic monitoring system for surface water quality has been accelerated, and more than 300 automatic water quality monitoring systems have been newly built each year.
Composition: The automatic water quality monitoring system is generally composed of monitoring station, sampling unit, water sample pretreatment system, online automatic analyzer system, control and management system, data acquisition and transmission system, remote data monitoring and management center, etc. 1). In addition, air compressors, pure water systems, UPS backup power supplies, AC regulated power supplies, video surveillance systems, lightning protection systems, automatic samplers, and waste liquid handling systems are also indispensable components for the normal operation of water quality automatic monitoring systems. section.
Control system: remote data management (central monitoring room) data acquisition and transmission unit analysis unit preprocessing and auxiliary unit sampling unit
Classification: According to the different automatic monitoring instruments, the automatic water quality monitoring system can be divided into four major categories: electrode method, wet chemical method, spectroscopy and biological class. Among them, the wet chemical monitoring system that monitors the indicators such as turbidity, conductivity, dissolved oxygen and chemical oxygen demand by adjusting the probe type and the monitoring of total phosphorus and total nitrogen by different chemical reagents is the most popular. According to different installation methods, the automatic water quality monitoring system can be divided into cabinet type, buoy type and vehicle type.
Principle: The electrode method is to put the measuring electrode into the water body and directly sense the value of a certain water quality parameter; the wet chemical method is to draw the measured water sample into the analyzer, and add various reagents according to different parameter analysis requirements. It is measured by internal electrodes and optical measuring instruments; spectroscopy is a continuous spectrum measurement in a wide frequency band in water samples. The molecules such as organic matter in the water sample absorb the emitted light to weaken its intensity, and the detector can measure a certain range of wavelengths. The absorption line and intensity of the photon pass through the water sample; the biological class uses the light-emitting diodes of different colors as the excitation light source to detect the change of the fluorescence intensity, and obtain the concentration of chlorophyll a contributed by different types of algae, thereby determining the chlorophyll a and the algae. The total concentration, as well as the concentration of various algae and its contribution to the chlorophyll a concentration curve.