Researches On Control System For Municipal Wastewater Treatment Based On Improved A~2/O Process

With the rapid development of our economic and urbanization, urban sewage discharge is growing rapidly. Large amounts of untreated urban sewage were discharged to surface water, leading to serious pollution of the water environment. The water crisis is worsening; water environment pollution and water shortage has become a serious constraint to sustainable urban development. To protect the environment, developing a suitable for china sewage treatment automatic detection and control system by using automation technology, computer technology, communication technology. It is integrated application of advanced instrumentation, automation devices, various new specialized equipment and the reliably PLC and computer, not only ensure the stability of the sewage treatment process, reliable and safe operation. But also improve the quality and efficiency of sewage treatment. It has great economic and social benefits to achieve our energy reduction.In this paper, by using the development of a urban sewage treatment plant project in Shandong as background, the development status of urban sewage treatment at home and abroad, the basic principles of urban sewage treatment system, the basic process and requirements for control system are analyzed. To achieve the goal of integrated enterprise automation, a suitable for china distributed sewage treatment control system is designed. The whole structure, function, design of software and hardware and implement of the system are introduced in detail.The dissolved oxygen (DO) play an important role in sewage treatment effect and energy saving. the control of DO is the most critical part of the sewage treatment plant. According to dissolved oxygen(DO) has the characteristics of nonlinear, big time-delay, big time-varying, and hard to get an accurate mathematical model and get satisfactory control effect by using routine PID control. A fuzzy-PID control system of DO is designed and implemented combining with the advantages of both PID and fuzzy control, using fuzzy rules to tune PID parameters in line. The software is compiled with VC. The simulation and applications show the system improves the anti-interference ability and adaptability to parameters’ changing; it has the advantages of stronger robustness, faster response and higher static accuracy.The urban sewage treatment control system designed this paper meet the requirements of modern water treatment in reliability and degree of automation, reducing the day-to-day management of the maintenance work and the cost. The system has put into running, and it has been checked and accepted. The effluent quality indicators have reached an A emissions standard GB18918-2002, It has bring about obvious society efficiency and economic efficiency and has greater promotional value.