Swirl technology: Proper design, application, and evaluation

Swirl and vortex technologies have been with us for over thirty years now, ever since Bernard Smisson incorporated a cylindrical vortex-type combined sewer overflow (CSO) regulator/settleable-solids concentrator into the Bristol, England sewerage system back in the early 1960`s. In the early 1970`s the U.S. Environmental Protection Agency (EPA) conducted a series of projects to develop and demonstrate swirl flow regulator/settleable-solids concentrator (swirl) technology. These projects resulted in the EPA swirl and helical-bend flow regulators/settleable-solids concentrators and the swirl degritter. New generations of this technology emerged after the EPA versions were developed including the Fluidsep{trademark} and the Storm King{trademark} vortex-hydrodynamic separators. However, despite different designs and applications, the main intent of the technologies are the same, i.e., to use the forces that arise from a change in flow direction to enhance settleable-solids separation from the storm flow. A variety of opinions have developed regarding the application of these technologies varying from overwhelming support to detractions that question their effectiveness. This abstract will show that proper design and placement in the sewerage system results in effective use of swirl technology. Reliable swirl pollution control efficiency determination is principally dependent on proper sampling and suspended and settleable-solids analysis techniques of the influent andmore » effluent. Simultaneous flowrate measurement is also important. Without the complete capture of heavy and stratified suspended solids (SS) across the influent flow channel or water column, the apparent performance of the swirl will be less than the actual. Particle-settleability tests which are presented, must be conducted before and after installation, but especially before in order to decide if the inertial characteristics of SS in the storm flow warrants the use of a swirl.« less