The Design And Implementation For Urban Sewage Treatment Distributed Control System

With the development of economy and the needs of sustainable development in ourcountry, sewage treatment has aroused much attention of the society. For sewage treatmentfactory, distributed control system can improve the treatment efficiency and the stability ofthe system, besides, it also can save energy and improve the economic benefits.Using the engineering project for sewage treatment system of zhanjiang garbage treatmentfactory as background, this paper introduce the overall design scheme and implementationmethod of the distributed control system. The sewage treatment plant uses the craft of A2Oand conducts sewage treatment30000tons per day. Sewage treatment distributed controlsystem is divided into three parts: the field level, control level and management level. Thefield level is the field instruments and control equipment, completing data acquisition andprocess control; Control level is PLC control station, responsible for the data processing andautomatic control; Management level is PC monitoring system, responsible for monitoring theprocess operation condition and remote control.According to the requirement of A2O, this paper introduces how to choose sensors andPLC, according to the control requirements, makes the PLC control program of the fielddevices. The control station chooses Siemens S7-300PLC and the server device uses PC.Through the PC monitoring system, the staff of the central control room can implementreal-time monitoring and adjusting. The interface of monitor is designed, using theconfiguration software KingView as tools. The interface includes login interface, overall flowdiagram interface, water intake system interface, reaction system interface, etc.The system network communication uses IE (Industrial Ethernet) and PROFIBUS-DPnetwork. PC connects with PLC through IE and PLC communicates with the field’s devicesthrough PROFIBUS-DP, configures the network hardware and make communication programto realize the communication system.Considering the sewage treatment process is time-variant, nonlinear and complex system,this paper proposed a control method combined PID control with the Fuzzy control system onthe oxidation ditch facilities and dissolved oxygen concentration control.This system has been put into operation, get good effect, and reach the control purpose.