Anaerobic Waste Water Treatment System

Mrunalini Kannan

2539239

Department of Electrical and Computer Engineering

Cleveland State University

Cleveland, Ohio-44114

EEC 640Spring 2011

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Anaerobic Waste Water Treatment System

Anaerobic wastewater treatment is a method for degradation of organic compounds by utilizing the action of anaerobic bacterial flora, which grows in wastewater, at an oxygen-free environment.

For an anaerobic treatment system, pH is an important environmental factor that can influence the activity of anaerobic bacteria.

In the final anaerobic stage process the methane bacteria need optimal pH range from 6.8-7.2

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pH Control System

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Mathematical Model

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Frequency Response Analysis

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Frequency Response Analysis

Methods Bode Plot Nyquist Plot

This gives a non-parametric, and model independent characterization of arbitrary order stabilizing controllers.

The result shows the frequency response of any stabilizing controller that must satisfy constraints on its magnitude phase and rate of change of phase at certain frequencies that are imposed by the frequency response .

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Continuation

Bode Plot Nyquist Plot

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Stability Analysis

The gain margin is 40.0632 and the phase margin is 91.7172.

For a system if both gain margin and phase margin are positive then the system is said to be stable.

The gain margin and phase margin of the anaerobic wastewater treatment system is positive.

Hence the anaerobic wastewater treatment system is stable.

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Time Response Analysis

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PID Control

Proportional-Integral-Derivative (PID) control offers the simplest yet most efficient solution to real world control problems.

A proportional-integral-derivative controller is a generic control loop feed-back mechanism widely used in industrial control systems.

PID controller calculates an error value as the difference between a measured process variable and a desired set-point.

The proportional, integral and derivative values can be can be interpreted in terms of time that is P depends on present error, I depend on accumulation of past errors and D is a prediction of future errors based on current rate of change.

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Continuation The popularity of PID controllers is due to their functional simplicity and

reliability.

They provide robust and reliable performance for most systems if the PID parameters are determined or tuned to ensure a satisfactory closed-loop performance.

The individual effects of these three terms on the closed-loop performance are summarized.

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PID Control

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PID Response

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Active Disturbance Rejection Control

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Estimated Mathematical Model

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ADRC Design

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Estimated Plant-ADRC Response

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Estimated Plant-Observer output

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Anaerobic Waste Water Treatment System- Mathematical Model, Parameters

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ADRC Design

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ADRC Response

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Stability Analysis

The stability is given by closed loop transfer function.

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Continuation

The characteristic Polynomial is

Coefficients in C(s) and H(s)

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Parameters and Transfer Function

The parameters and the transfer function to see the stability of the system is shown

The stability is checked using the bode plot and nyquist plot

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Responses/Plots

Bode Nyquist

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Gm =4.3420Pm =97.7024⍵gc =142.8642⍵pc =37.7915

Stability Analysis

Since the gain margin is positive the system is stable. The gain cross-over frequency and the phase crossover frequency are also positive. Hence the system is said to be stable.

From the nyquist plot it could be said that the system is stable.

Hence from the frequency response analysis it could be said that the system is stable and robust.

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ADRC

WHY?

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Comparison of PID and ADRC

PID Simplicity Robustness Not inherent Covers treatment to both transient

and steady state response Applies to linear systems Tuning of three values is difficult Has Maximum overshoot Settles after a long time.

ADRC Simple Robustness against dynamic

variations and external disturbances Inherent due to the fact that

controller is not dependent on accurate mathematical model

Applies generally to non-linear and time varying systems with SISO or MIMO

Tuning a single value is easy Has comparatively less overshoot Settles immediately and has good

settling time

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Comparison of PID and ADRC

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Victory for ADRC

From the comparative response it is noted that ADRC has less overshoot and good settling time than PID control.

Conclusion

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References Cascade Control of the PH in an Anaerobic Wastewater Treatment System Kang

Jiayu，Wang Mengxiao，Mi Linan and Xiao Zhongjun Shannxi University of Science & Technology Xi’an, China.

Implementation of Matlab-SIMULINK Based Real Time Temperature Control for Set Point Changes, Emine Dogru Bolat 5/11/2011

PID Control System Analysis, Design, and Technology, Kiam Heong Ang, Gregory Chong, Student Member, IEEE, and Yun Li, Member, IEEE

16th IEEE International Conference on Control Applications Part of IEEE Multi-conference on Systems and Control Singapore, 1-3 October 2007, Frequency Response Analysis of Active Disturbance Rejection Based Control System Gang Tian1 and Zhiqiang Gao1,2

Scaling and Bandwidth-Parameterization Based Controller Tuning Zhiqiang Gao Dept. of Electrical and Computer Engineering Cleveland State University, Cleveland, Ohio 44115 

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