Stilling Pond Storm Overflow Studies

A model stilling pond storm water overflow was tested with a side-wall siphon towards the upstream or downstream end. Light solids were retained in the pond and heavy solids moved to the outlet giving in general 100% efficiency, but solids of specific gravity 0.9 to 1.1 were critical and invariably resulted in lower efficiencies, efficiency being taken as the proportion of solids passing downstream to the treatment works. Working with a constant inflow and with the siphon downstream was better than with the siphon upstream. With the downstream siphon, the best position of the baffle, giving 90% efficiency for solids of critical gravity, was 0.2 L from the upstream end at a vertical position of 0.3 − 0.63 H, in which L and H = the length and height of the pond.