The flow energy of the fluids in many treatment process can be used to advantage in a hydraulic separator. In this type of separator, flow from a pipe or a channel is inject tangentially into a circular basin and the flow energy is converted to “rotational” flow in the basin.
The rotational flow can be controlled using vanes and other in-basin features to encourage the system to act as a low-speed cyclone. The rotational flow allows the larger particles (usually granular materials such as sands and fine gravels) to fall rapidly into a sump. The smaller particles are retained in the flow for longer than they would be in a rectangular tank (due to the rotational flow component) and these too can be separated by gravity settling in another zone of the chamber.
An additional advantage of this method of separation is that the same mechanism used for “settling out” particles of specific gravity greater than water, can also be used to “float off” lighter materials such as oils and grease which can be skimmed from the surface of the clarified water. The hydraulic separator thus forms a useful barrier device and with no moving mechanical parts, it can be operated in a fail-safe mode when there is a need to design to intercept specific materials, during specific events.
Blue Hill Hydraulics uses CFD to optimize the design of devices used for stormwater interception and to retain granular material in specially designed gully-pots. Devices not unlike these, are also used in the oil industry for gas, water, and oil separation.