DESIGN AND CONTROL OF PH LEVEL IN WASTEWATER USING FUZZY LOGIC CONTROLLER

Abstract

The demand for application of advanced control strategies for process industries is increasing rapidly due to complex nature of industrial processes. The demand also increases to achieve improvement of the product quality and environmental factors. One such example of complex process is the pH neutralization process. This work presents the process to simulate the control system of pH level by adding acid or base (alkali) into a process tank in a wastewater system to maintain the pH level to neutral value, which is pH 7. The controller should be designed in such a way that neutral output of the system is obtained. The pH neutralization process is highly nonlinear and has time varying characteristics where gain changes by several order. Hence controlling the value of pH is considered to be difficult and depends on nonlinear control techniques. Classic PID (proportional-integral-derivative) controllers are the most popular control system present in industrial plants although they are not suitable for applications in non-linear systems. On the other hand, fuzzy logic properly deals with system non-linearity and uncertainties where frequent changes at the operation point and disturbances occur. So our work is done based on fuzzy logic controller. The system is developed in Simulink/MatLab® software. It emulates a real plant through the use of the fuzzy inference toolbox of this software. The results are presented and lead to conclude that the fuzzy system is appropriated to systems with non-linear characteristics like pH regulation in waste water treatments.