Model Study of Jet‐Circulated Grit Chamber

Abstract

Experiments were carried out in a reduced‐scale pilot‐plant model of a grit chamber, having a cross‐sectional geometry similar to that of a conventionally aerated grit chamber. The model using clear water was built on a geometric scale of 1:4. Nozzles along one wall of the chamber injected jets of water, which caused a helical rotating motion of the water in the chamber. Three sizes of nozzles were tested, as well as two nozzle spacings. Water velocities at various points were measured under different operational conditions. A consistent correlation between power input and transverse bottom velocity was derived for the model grit chamber. This correlation enables the calculation of power input, which is required for a desired bottom velocity. It was concluded from the operation of the model that water jets can replace air diffusers used in conventionally aerated grit chambers. This system may reduce odor nuisance, which is caused by aeration in the conventional design.