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Intelligent control is an advanced stage of the development of automatic control. It is a highly comprehensive and integrated integration of artificial intelligence, cybernetics, systems theory and information theory. It mainly includes fuzzy control, neural network control, learning* control and expert control etc. The application of intelligent control in various unstable dynamic engineering systems is becoming increasingly widespread and in-depth, especially the research and application results achieved in recent years have attracted more attention. Since the operating costs of sewage treatment are huge and long-term, if the operating costs of urban sewage treatment plants can be saved by 1% through effective control, it is an astronomical figure. It can be seen that it is very necessary to strengthen the research on intelligent control of urban sewage treatment system. 1 Analysis of the current status of automatic control technology at home and abroad Developed * * After the popularization of secondary treatment, a large amount of money and scientific research force were invested to strengthen the monitoring, operation and management of sewage treatment facilities, and realized computer control, alarm, calculation and instant recording. The United States began to realize automatic control of sewage treatment plants in the mid-1970s. At present, major sewage treatment plants have realized automatic testing and control of main parameters in the process flow. Since the 1980s, two international academic conferences on water treatment instruments and automation have been held in the United States. Hundreds of papers published at the conference reflect that water treatment automation has developed to a practical level. Compared with foreign countries, my country's sewage treatment automation control started relatively late. In the 1990s, sewage treatment plants began to introduce automatic control systems, but most of them directly imported complete sets of foreign automatic control equipment. Domestic automatic control systems are rarely used in sewage treatment plants. In recent years, scholars at home and abroad have conducted research on automatic control processes for sewage treatment in order to seek more accurate and reliable methods to implement automatic control. Zipper et al. developed an automatic control system suitable for small sewage treatment plants, which uses a controller based on oxidation-reduction potential (ORP). This controller works automatically and can optimize between nitrification and denitrification, thereby reducing energy consumption. They found in the pilot test that the actual load of the sewage treatment plant has a strong correlation with the ORP curve change. The use of two-point ORP control ensures that the ratio of nitrification time to operating time increases as the load increases, which lays the foundation for the development of control rules for small sewage treatment plants. John et al. used two SBR reactors to treat poultry production wastewater and evaluated their treatment efficiency. They also examined the relationship between denitrification and reactor ORP, and used advanced instrumentation for real-time pH, ORP and DO monitoring and process control to control the aeration time based on the ORP set value. When treating variable-component wastewater, this study not only achieved stable effluent quality, but also relied on ORP to control the aeration time and reduce the operating time of the air compressor. Yu et al. designed and studied a continuous water-feed SBR reactor with real-time ORP and pH control system. The real-time monitoring and control system consists of sensors, computers, human-machine dialogue interfaces and control components. Four ORP meters with Ag/AgCl electrodes, a DO meter and a pH meter are installed in the SBR reactor. The analog signals of the sensors are converted into digital signals through an AD/DA converter, and a computer is used to collect the signals every second. After the computer analyzes the collected data, it passes it to the relay through the control circuit, which turns on/off the mixer, decanter and blower. The test results show that the SBR reactor using real-time control is better than the SBR reactor using time sequence control in terms of substrate removal efficiency and energy consumption reduction. Puznava et al. introduced real-time aeration control in a simultaneous nitrification/denitrification biological filter, and established feedback control based on DO online monitoring and series control based on ammonia nitrogen and DO online monitoring. Compared with the traditional nitrification-denitrification biological aeration filter (BAF), the aeration volume of the biological filter using real-time aeration control is lower than 50% of the traditional method when achieving the same treatment effect (effluent TN <20mg/L). Wang Shuying proposed a SBR method for organic matter concentration control based on the existing time and flow program control abroad, making the control process more quantitative and precise. The water quality of industrial wastewater changes greatly. When the concentration of organic matter in the incoming water is high, in order to make the effluent water quality meet the standard, the reaction time should be appropriately increased to make the operation more reliable. ； When the concentration of organic matter in the incoming water is low, the reaction time can be reduced to save operating costs. The research results of Peng Yongzhen and others who used ORP as an indirect indicator of the degree of organic matter degradation in SBR reactors showed that whether the aeration volume or MLSS concentration was changed within a wide range, or the initial COD of the reaction was gradually changed or changed suddenly between 230 and 2180 mg/L, when the COD reached a refractory concentration, the ORP increased rapidly and significantly, and then quickly stabilized and stabilized within a certain range. Therefore, ORP can be used as the computer control parameter of the reaction time of the SBR method to realize computer online automatic control. Through the above analysis, the following problems exist in the current automatic control of sewage treatment:: ①Traditional sewage treatment automatic control systems require the establishment of accurate mathematical models and propose that some relatively stringent linearization assumptions must be followed. However, due to the complexity, nonlinearity, time variability, uncertainty and incompleteness of actual sewage treatment systems, it is generally impossible to obtain accurate mathematical models and assumptions that are consistent with reality. Therefore, sewage treatment automatic control systems established using traditional control theories have problems such as large fluctuations in effluent water quality in practical engineering applications. ②The functions of some automated testing equipment and instruments used in the sewage treatment automatic control system are still very imperfect. In actual testing, they fail to achieve the expected results and have large errors. Therefore, relying on these testing equipment to judge the sewage treatment situation and implement automatic control is often difficult to achieve the purpose of treating water quality and discharge up to standard and saving energy. ③Many scholars at home and abroad have conducted many real-time control studies to improve the treatment efficiency and reduce energy consumption of sewage treatment plants, such as using ORP, DO and pH values as control parameters to control effluent water quality and reduce aeration volume. However, these methods also have some problems, such as controlling nitrification-denitrification in sewage treatment plants. It is difficult to determine the ORP used in the process, so most sewage treatment plants based on ORP control also implement time control as emergency control when the controller cannot find the ORP characteristic point. This results in many sewage treatment systems actually still using time to control the entire treatment process. ④The automatic control of sewage treatment is different from other control systems. It requires the control of a large number of valves, pumps, blowers and mud suction (scraper) machines, agitators in aeration tanks and sludge digestion tanks, as well as the input and discharge of sludge in sedimentation tanks and digestion tanks. Therefore, sewage treatment plants need to control a large number of switches automatically, and they often need to be controlled according to certain requirements. Time or logical sequence to start/stop at a scheduled time. However, there are some problems with the quality of the valves produced in my country at present, and their service life is short. If imported from abroad, the price is very expensive, and it is difficult for general sewage treatment plants to afford it. Therefore, the author believes that the main reason that restricts the development of automatic control of sewage treatment in my country is not the production process problem, but the equipment problem.