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The present paper deals with the issue of measurement delays which constitute a very prominent problem faced by most control systems. The system considered is that of a bioreactor used for the biological treatment of wastewater. The recording of the output substrate concentration of such systems usually involves a delay which results from the dependency of the flow of the liquid on its consistency. A PI observer-based control is applied and its performance is analysed in terms of the maximum delay for which the system is stable and converges as well as in terms of the convergence times. Based on these parameters, the results are compared to those obtained by a feedback linearising observer-based system. This comparative analysis showed that the PI controller performed better than the feedback controller, hence confirming its efficiency in biomass regulation in the presence of delayed measurements.

This paper proposes the application of a Proportional-Integral (PI) controller for the observer-based regulation of biomass concentration for a continuous-discrete system. An observer is essential to estimate the values of biomass concentration since the controller depends on these measurements. The analysis focuses on the continuous-discrete nature of the system which is represented by a continuous bioreactor system with discrete output measurements. The maximum allowable sampling partition diameter is determined along with the corresponding convergence time. These results are then compared to another work that used a feedback linearising control to achieve biomass regulation. The results obtained with the PI controller proved to be far more superior both in terms of maximum possible sampling time and convergence time. These findings confirmed the satisfactory and improved performance of the proposed observer-based controller.

This work provides the observation and control of biomass concentration in Waste Water Treatment Plants. To achieve this, a PI controller was designed together with an observer to form an observer-based control system. The optimal values of the proportional gain and integral gain were determined to obtain the convergence of the observer in the least amount of time without compromising on the time taken by the response to reach steady state. Encouraging results which shall provide a basis for further and more in-depth research on the system were obtained.

In this paper, an observer-based control system is presented for the regulation of biomass concentration in bioreactors. The importance of the observer is highlighted by the dependency of the feedback linearising controller on the measurements of biomass concentration. Further, the discrete nature of output substrate concentration is considered and the performance of the system proposed is analysed through a simulation study using Matlab/Simulink. This study is also used to determine the limit on the sampling partition diameter for which the observer and controller designed give satisfactory performance. The implemented observer-based control system showed satisfactory performance both in terms of stability and convergence for given values of sampling partition diameters.