Longitudinal Mixing in Spiral Flow Aeration Tanks

The dispersed plug flow model was found to characterize the experimental response curve of a full scale aerator. The extent of mixing observed was found to be independent of the liquid detention time over the range of values employed in the activated sludge process. Similarly the type of diffuser, fine or coarse bubble, did not significantly influence the level of mixing. The level of mixing existing in aerators of various geometric configurations was found to be a function of the airflow rate per unit volume and the cross-sectional geometry. The concentration profile of a substrate for a first order reaction was calculated for various levels of mixing. The influence of this longitudinal variation of concentration on the requisite airflow distribution along the length of the aerator was analyzed.