Effect of Pond Depth on Bacterial Die‐Off

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 1.0×2.0m. 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. It was concluded that the pond depth has a significant effect on the coliform die‐off rate. The first‐order die‐off rate constant was found to be inversely proportional to the first power of the pond depth.