Research On Aeration System Control Of Wastewater Treatment Plant

With the continuous development of society and economic, the amount of urban waste water has been increasing all the time. Wastewater treatment industry has attracted more and more people’s attention. Currently, biological treatment technology is widely used in wastewater treatment, which is relied on microbes in biochemical decomposition of organic matter in wasterwater. To maintain aerobic biological environment by aeration is the key segment, because the amount of aeration directly affect water quality and wastewater treatment plant energy consumption, so the research on aeration system control has important practical significance.This thesis takes biological treatment systems of wastewater treatment plant as the research background, and it makes a deep research on aeration system of the activated sludge treatment process. Through the analysis of wasterwater quality testing index, it has determined to use dissolved oxygen concentration as aeration process control parameters. As the sewage inputs are random variables and the external environment has many uncertain factors, such as water quality, quantity and temperature changes in water and other factors, moreover, the mechanism of biochemical reactions and dissolved oxygen homeostasis process are very complex, with a longer lag time, a non-linear nature and time-varying characteristics, so it is difficult to establish accurate mathematical model. The thesis establishes a similar model based on the approximation and empirical data, and analyses single-loop PID and cascade PID control system. Since fuzzy control does not depend on an accurate model of the controlled object, this thesis attempts to design fuzzy PID controller based on cascade PID control system. It not only maintains the simple, adaptable advantages of PID, but also self-regulates the PID controller parameters to adapt to changes in the aeration process model parameters. To simplify the initial domain of the fuzzy controller and improve control accuracy, this thesis attempts to design a variable universe fuzzy PID controller to control the aeration system.Finally, the thesis uses the matlab to simulate the aeration control system and analyses the tracking property of variable universe adaptive fuzzy PID control system. The simulation results indicate that the variable universe fuzzy PID controller not only has smaller overshoot and shorter settling time, but also has better anti-interference ability and adaptive capacity. It can achieve good control effect.