Spiravac Clarifier

The Spiravac is a peripheral feed clarifier designed for superior solids removal through suction orifices to ensure rapid return of active sludge to the process. The wastewater enters the outer perimeter of the clarifier tank and is directed along the narrow raceway formed by the skirt and the outer wall. This flow pattern dissipates the wastewater’s hydraulic energy as it flows around the raceway, eventually spiraling down underneath the skirt and into the main settling area. The flow travels inward from the skirt towards the center of the tank, coinciding with the direction of the sludge, and the clarified water rises into the centrally located effluent weir trough. The combination of the spiraling flow pattern and the skirt eliminates all possibility of short-circuiting and provides better utilization of the total tank volume for more effective settling.

The Spiravac Clarifier is available in two designs; the Controlled Removal (Type CR) which utilizes individual sludge removal pipes and adjustable riser pipes in a revolving sludge well, or the Direct Removal (Type DR) which uses a common header pipe with orifices that removes sludge to a rotating manifold at the center of the tank for withdrawal.


  • Ensures rapid removal of active sludge to the process
  • Operators can control the flow from each sludge removal pipe (Type CR)
  • Hydraulic flow pattern minimizes problems usually associated with center-feed clarifiers, such as waterfall effect, sludge wall creep and short circuiting
  • Suspended solids are retained in the sludge blanket as flow travels underneath the skirt
  • Independent laboratory tests confirm peripheral-feed spiral clarifiers perform two to four times better hydraulically than center-feed clarifiers.