Design And Research Of Automatic Monitoring And Control System For Sewage Treatment

With the improvement of living standards and the needs of sustainable development, 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 quality and efficiency of sewage treatment, and save manpower and raw materials, it is very necessary to research and design a batch of automatic control systems of sewage treatment, which can meet the requirement of emission standard and run efficiently and economically, and is with high degree domestic and high automatic level.This paper introduced the typical process of sewage treatment, and explained the basic methods and principles of the urban sewage treatment according to the process flows briefly; analyzed the composition of automatic control systems for domestic sewage treatment domestically, and compared factory integration mode of systems with automation and management integration mode; analyzed the selection of PLC (Programmable Logic Controller), which is the most important part of automatic control systems, and concluded the "4+1+N" selection set mode of PLC station, which is composed of 4 basic PLC stations such as pretreatment system PLC station, biological treatment system PLC station, sewage disinfection system PLC station, sludge dewatering system PLC station, and 1 PLC station for aeration system, and other PLC stations for sewage recycle; analyzed the network structure of the communication systems in the automation control system and its communication protocol configuration; given the commonly used typical layout of inspection instruments in the sewage treatment plants according to sewage treatment process and control requirements; concluded a typical procedure for video monitoring systems in sewage treatment plant.Control schemes for each process section of sewage treatment directly determine the effect of sewage treatment. This paper analyzed and summarized most control schemes for major facilities, including period control and level difference control for mechanical grilles, split range control by liquid level for lift pumps, period control for grit chambers, period control for primary sedimentation tanks, PID (Proportion, Integration, and Differentiation) control or PID parameter fuzzy tuning control for aeration systems, split range control by sludge level for secondary sedimentation tanks and so on.Meanwhile, take the second sewage treatment plant in YunCheng as an example, the paper specified how to design a automation control system for sewage treatment plants. It gave a design scheme including PLC station selection, layout of inspection instruments, communication system design, video monitoring system design, control center design, modular design of PLC control procedure, and controlling procedure of upper computer design.