Research On Distributed Control System Of Municipal Wastewater Treatment

Taking wastewater treatment plants in certain one city of Heilongjiang as anexample, by introducing the CASS(cyclic activated sludge system) treatmenttechnology and advantage which were used by this plant, a set of DCS systemmeeting the requirements of the plant were designed based on the characteristicsof field instrumentation and control object.The structure of the system wasdiscussed in detail in the paper. Based on the structure, Process Control, CentralControl and Production Management were described in detail. The design part ofthe system was divided into the design of host computer and the design of lowercompute. The whole control system was divided into four PLC sub-stations bylower computer. Based on the characteristics of each sub-station the hardwarewas disposed, the address was chose and the hardware configuration wasdesigned. Adapting the King SCADA configuration software, the host computercompleted the real-time data acquisition for instrument operating conditions ateach processing chain. Further the process flow was displayed, the data of testingwere recorded, the variable trend chart of water quality parameters was analyzedand field failure was diagnosed promptly and alarmed. It can complete advancedcontrol strategies which did not complete by artificial.The communicationbetween host computer and PLC was completed by Combination of industrialEthernet and field bus.Finally, the controlling process of dissolved oxygen (DO) in WastewaterTreatment was analyzed theoretically. Considering the characteristics of puredelay, large inertia and uncertainty, the fuzzy intelligent control system was ledinto the traditional PID theory. The fuzzy controller of dissolved oxygen (DO)was designed and simulations were done using the Matlab.The simulation resultsshown that the controlling system had smaller overshoot, faster response speed, better stability after using the adaptive fuzzy PID controller.