Dynamic analysis and optimal feedback control synthesis applied to biological waste treatment

Abstract

The dynamics and optimal feedback control of biological waste treatment processes are examined. Modern feedback control theory is applied and results are obtained for both proportional and proportional plus integral control. A dynamic mathematical model of the system is developed by employing a Monod kinetic model, which is modified to account for endogenous metabolism, and a complete mixing flow model in the growth chamber. The feedback control is implemented via the flow rate so as to maintain desired effluent concentrations. External disturbances which cause changes in substrate concentration and/or cell concentration are considered and optimal control effort is applied. Results are also presented for impulse and step changes in the influent substrate concentration. It is found that by changing the values of the weighting factors in the objective function, it is possible to obtain good control of either the effluent substrate concentration or cell concentration.