污水处理过程溶解氧浓度的自抗扰控制

溶解氧是活性污泥法处理污水的一个关键变量,它关系到污水中有机物的生物降解、微生物生长和出水水质.多数污水处理过程选择溶解氧为被控量.然而,溶解氧浓度受进水流量,进水组分、浓度波动等诸多因素影响,较难控制.本文根据曝气量变化确定溶解氧浓度设定值,以污水进水变化率为控制量,设计线性自抗扰控制实现对溶解氧浓度的跟踪,进而获得对污水出水底物浓度的间接控制.设计两组仿真实验,分别模拟进水底物浓度固定和变化时,线性自抗扰控制对溶解氧浓度和出水底物浓度的控制;同时,设计仿真实验验证线性自抗扰控制对总扰动的估计和补偿效果.仿真结果表明,线性自抗扰控制可获得良好的溶解氧浓度跟踪和出水底物浓度控制效果;在进水水质波动时,线性自抗扰控制亦具有很强的干扰补偿能力,可保证出水水质.

Control of dissolved oxygen for a wastewater treatment process by active disturbance rejection control approach

Dissolved oxygen (DO) is a key parameter in activated sludge wastewater treatment processes. It relates to the biodegradation of organic compounds, the growth of microorganisms and the effluent quality. DO is always taken as a controlled variable in wastewater treament processes. However, DO concentration is sensitive to many factors, such as the rate of inflow, component of inflow, variation of concentrations. The control of DO concentration is a difficult problem in control engineering. Desired DO concentration is assigned by aeration rate, and dilution rate is taken as the control input. Linear active disturbance rejection control (LADRC) is designed to make DO concentration tracks the setpoints, and, indirectly, the substrate concentration is controlled within an acceptable level. Two cases, i.e. fixed and varied influent substrate concentrations, are considered in simulations. Additionally, in order to verify the disturbance rejection and compensation ability of LADRC, a group of numerical simulation is also performed. Numerical results show the fact that both DO concentration tracking and substrate concentration regulation can be realized effectively by LADRC, and LADRC is also able to reject the disturbance and guarantee the effluent quality even if the influent wastewater are fluctuated.