Design And Research Of Automatic Monitoring And Control System In Guiyang County Sewage Treatment Plant

With the improvement of living standards and the needs of sustainable development strategy, sewage treatment has aroused much attention of the society. It can play a role in environmental protection, and can deal with water reuse to conserve water resources. In order to improve the efficiency and quality of sewage treatment, and save manpower and raw materials, designing an automatic monitoring system is very necessary.This thesis takes Guiyang County Sewage treatment plant as an example, introducing the process,character and technical criteria of Carrousel 2000 Oxidation Ditch.The control system selection and design is according to the actual on-site equipment and the control objects' characteristics, composing two level computerized distributed control system composed by the on-site control level and process control level, so that the production process information can be centralized and decentralized control, improving the system reliability. This system takes SIEMENS Corporation's S7-300 and S7-200 as data acquisition and the control unit, using Microsoft Corporation's Visual C# 2008 to develop Upper Computer Software, Upper Computer communicate with each control unit through PROFIBUS Fieldbus. Upper Computer and control units coordinate each kind of examination measuring appliance and the control device to collect, monitor, analysis and process the data of several control quantities—sewage fluid position, current capacity, pH, temperature and dissolved oxygen concentration. This paper elaborated on the functions of the control systerm's structure, hardware configuration, monitoring software and video monitoring System, and described the design pinciples of sewage treatment plants' video monitoring System and communication network integrating several kinds of communication protocols.The dissolved oxygen (DO) which is an important parameter of attribute water quality in the process of sewage treatment is the focus of control. But because the volatility of sewage components is quite big, the dissolved oxygen is also the difficulties in the process of control. Based on the massive researches on control objects and combining with the DO control experience of other sewage treatment projects, this thesis decides to use fuzzy PID control algorithm which combines fuzzy control with commonly used PID control to control the process of air blower's opening so that the content of DO is controlled in certain scope.This system has been adopted by the Guiyang County Sewage treatment plant,operating in good condition and has served the anticipated control purpose. It is economically and socially significant.