Abstract
The depth dependence of bacterial die-off was demonstrated experimentally both in batch models and in three pilot-scale waste stabilization ponds with water depths of 0.5 m, 1.0 m, and 1.5 m. The dimensions of the ponds in plan were 1.0 x 2.0 m. The ponds were fed with secondary effluent of a two-stage trickling filter plant. An activated sludge treatment plant effluent was used in the batch models. The pond depth apparently had a significant effect on the coliform die-off rate. The first-order die-off rate constant was inversely proportional to the first power of the pond depth. (Author 's abstract)