Development of better design and control methods is an obvious way for
improving plant operation and performance in an activated sludge proc
ess. A different approach to the control systems in the activated slud
ge wastewater treatment process is presented. This system is based on
the control of the sludge age (Theta(c)) and the microorganism concent
ration (MLSS) in the aerator, by adjusting the sludge recycle and wast
age flow rates, respectively.