Compartmentalization of Aeration Tanks

It has been shown theoretically that an activated sludge process in which longitudinal mixing in the aeration tank is suppressed should produce a better quality effluent than one in which the contents of the aeration tank are well mixed. The results of a laboratory investigation to confirm this theoretical prediction are presented. The experimental studies were conducted using a laboratory-scale activated sludge unit. Longitudinal mixing in the aeration vessel was controlled by dividing the vessel into compartments. Tracer experiments were used to determine the level of mixing under different operating conditions. The biological experiments were conducted using samples of activated sludge and a skim milk solution as the feed medium. The results of the tracer experiments showed good correlation with the previously presented mathematical model. The results of the biological experiments showed that the mathematical model provides a reasonable prediction of sludge growth in the aeration vessel but that the predictions of effluent quality from the model are not as accurate as might be desired.