The Research Of Data Driven Piecewise Sliding Mode Control For Municipal Wastewater Treatment Process Sludge Bulking

With the rapid development of economy and the advancement of urbanization,municipal wastewater discharge has increased year by year.The water safety of urban residents has been seriously affected by the deterioration of water quality.Municipal wastewater treatment process(WWTP)has become an important initiative to realize the recycling of wastewater and improve the utilization of water resources.Activated sludge process,involving physical,chemical and biological reaction processes,is widely used for WWTP at home and abroad.However,loose structure and poor precipitation compression performance of activated sludge are easy to occur in activated sludge process,which leads to sludge bulking abnormal condition and affects stable operation of WWTP.Therefore,it is an urgent problem to study control method for sludge bulking in WWTP,overcoming the influence of sludge bulking abnormal condition and ensuring the safe and stable operation of WWTP.It has important theoretical significance and practical application value.To overcome the instability problem of WWTP caused by sludge bulking abnormal condition,a data driven piecewise sliding mode control method is proposed.Firstly,the process flow and reaction mechanism of WWTP are analyzed,and the collection method of main data variables is described.Secondly,an operating condition identification model,based on fuzzy neural network,is designed to online identify sludge status.Thirdly,a data driven piecewise sliding mode controller is designed to realize stable control of WWTP when sludge bulking abnormal operating condition occurs.Finally,the piecewise sliding mode control system for WWTP,based on the previously designed algorithm,is constructed by selecting suitable equipment,which is verified in a small test platform to ensure the safe and stable operation.The main research works of this thesis are as follows:1.Operating condition identification model based on fuzzy neural network for WWTP: For the problem that the sludge volume index cannot be detected in time and it is difficult to online evaluate sludge status,an operating condition identification model,based on fuzzy neural network,is proposed to online identify operating condition for WWTP.Firstly,the main variables and their data characteristics are analyzed to determine output variables and input variables of the operating condition identification model.Secondly,a partial least square method is applied to select feature variables,which realizes the dimensionality reduction of input variables and improves the rapidity of recognition on the basis of ensuring the accuracy.Finally,the selected variables and the sludge volume index are taken as the input variables and output variable of fuzzy neural network,which completes real-time judgment of operating condition in WWTP.2.Data driven piecewise sliding mode controller for WWTP of sludge bulking:A data driven piecewise sliding mode controller is proposed to overcome the adverse effects of sludge bulking in different degrees and improve the operating performance of WWTP.Firstly,the control model under different operating conditions is established.Secondly,according to the specific operating condition,a piecewise sliding mode control method is designed to adjust the concentration of dissolved oxygen and nitrate nitrogen to eliminate sludge bulking and realize stable control of WWTP.Thirdly,the boundary condition of piecewise sliding mode controller is analyzed.The stability of proposed method is proved on the basis of boundary condition.Finally,the effectiveness of control method is verified on the benchmark simulation platform.3.Piecewise sliding mode control system for WWTP: In order to verify the effectiveness of piecewise sliding mode controller to overcome sludge bulking abnormal condition,a piecewise sliding mode control system for WWTP is developed.Firstly,the operating environment of piecewise sliding mode control system for WWTP is analyzed,which lays a foundation for equipment selection and algorithm configuration.Secondly,according to the actual situation,the control algorithm is achieved by selecting supporting equipment.Finally,the piecewise sliding mode control system is applied to a pilot platform,and results show it can realize stable operation of WWTP.