Theoretical Analysis of Activated Sludge Dynamics

A mathematical model of the completely mixed activated sludge process was subjected to analog computer simulation in an attempt to characterize progress response to perturbations of input flow rate, input BOD concentration, and sludge recycle ratio. All parameter values used were typical of those reported in the literature. Response was measured as the speed with which the system adjusted to a given disturbance. Results indicate that the effluent BOD concentration should be a predictable function of the influent BOD mass rate, for a given operating state. From the standpoint of process control, results indicate that control can best be achieved through modulation of influent flow rate. Control through adjustment of sludge recycle was found to be the least effective. Implications of the findings to alternative process designs are discussed.