Design of modified digital PWM controller for aeration in wastewater treatment process

The activated sludge process (ASP) is widely used in many wastewater treatment process (WWTP), which consists of a biological reactor and a sedimentation tank, and also is used to take the contaminant (substrate) away by means of activated sludge (microorganisms). The first part of this paper gets the simplified model of the activated sludge model No.1 (ASM1), which contains the nitrification and denitrification. Because of the nonlinear nature of ASM1, the optimal linearization technique is applied to it for finding a local optimal linear model, which has the same dynamics of the original nonlinear model at the operation point of interest. Then, a discrete-time optimal control law in pulse-amplitude-modulated (PAM) is designed using linear quadratic regulator (LQR) method. For engineering implementation, a modified pulse-width-modulation (PWM) method is proposed. At last, some simulations are made to demonstrate the effectiveness of the proposed control strategy, which can reduce the whole operational energy and spend less reaction time, comparing to Multi-set point on/off control and PWM control techniques.

[1]  Mircea Vasile Cristea,et al.  Cost reduction of the wastewater treatment plant operation by MPC based on modified ASM1 with two-step nitrification/denitrification model , 2011, Comput. Chem. Eng..

[2]  Junfei Qiao,et al.  Adaptive dissolved oxygen control based on dynamic structure neural network , 2011, Appl. Soft Comput..

[3]  Leang S. Shieh,et al.  Digital modeling and control of multiple time-delayed distributed power grid , 2012 .

[4]  Emil Petre,et al.  Neural networks-based adaptive control for a class of nonlinear bioprocesses , 2010, Neural Computing and Applications.

[5]  Alain Rapaport,et al.  Optimal time switching control for multi‐reaction batch process , 2010 .

[6]  L. Shieh,et al.  Digital controller design for absolute value function constrained nonlinear systems via scalar sign function approach. , 2010, ISA transactions.

[7]  B. Carlsson,et al.  Optimal aeration control in a nitrifying activated sludge process. , 2012, Water research.

[8]  V. Bartolozzi,et al.  Expert control of DO in the aerobic reactor of an activated sludge process , 2001 .

[9]  M. C. Castro,et al.  Reduction of aeration costs by tuning a multi-set point on/off controller: A case study , 2011 .

[10]  Wei Ding,et al.  PWM digital control of aeration in wastewater treatment process , 2013, 2013 25th Chinese Control and Decision Conference (CCDC).

[11]  B. Holenda,et al.  Dissolved oxygen control of the activated sludge wastewater treatment process using model predictive control , 2008, Comput. Chem. Eng..