Operation - Aqua-Swirl™ Hydrodynamic Separator
The Aqua-Swirl™ is designed to provide a high level of water quality treatment through the use of a single swirl chamber. Operation begins when stormwater enters the Aqua-Swirl™ by means of its tangential inlet pipe thereby inducing a circular (swirl or vortex) flow pattern. The swirl chamber represents the effective treatment area of the device where both the capture and retention of sediment, debris and free floating oil occur. A combination of gravitational and hydrodynamic drag forces results in solids dropping out of the flow. Particles settle and migrate to the center of the swirl chamber floor where velocities are the lowest. The captured (settled) particles are retained in a cone shaped sediment pile at the base of the swirl chamber. The treated flow exits the swirl chamber behind an arched inner baffle that is positioned opposite the influent pipe and in front of the effluent pipe.
The top of the baffle is sealed across the treatment channel to eliminate floatable pollutants from escaping the swirl chamber. A vent pipe is extended up the riser to expose the backside of the baffle to atmospheric conditions, thus preventing a siphon from forming at the bottom of the baffle. Water is retained within the swirl chamber between storm events to a level equal to the invert elevations of both the influent and effluent pipes.

An offline Aqua-Swirl™ configuration uses a separate diversion structure, or weir device located upstream of the unit. The diversion structure is designed to direct only the designed water quality treatment flow through the swirl chamber. Twin or multiple Aqua-Swirl™ system configurations can be implemented to allow for higher treatment flow capabilities beyond that of a single unit.

An inline (online) configuration uses an internal conveyance flow diversion (CFD) design to provide full treatment for the most contaminated first flush, while the cleaner peak storm flow is diverted and channeled through the main conveyance pipe. The CFD design can be compatible with retrofit applications. Local stormwater guidelines should be reviewed to determine whether a CFD system can be used in lieu of an offline water quality treatment unit.