Fixed Decanters Fixed Decanters Fixed Decanters Fixed Decanters Fixed Decanters Fixed Decanters

Fixed Decanters

Fluidyne’s patented fixed solids excluding decanter is the key component in our ISAM™ and SBR processes providing the highest effluent quality. The decanter has no moving parts. Therefore there is nothing in the basin to service or maintain. Since it is submerged, it cannot freeze, it cannot pass floating solids, and there are no odors. The decanter is fabricated out of either stainless steel or fiberglass depending on the size and application. Fixed decanters are designed to last 25 years without the need for replacement.


During all times except when decanting, air is trapped in the decanter forming a positive seal. After sludge has settled in the basin, an electric operated ball valve opens releasing air from the decanter. This procedure acts as a siphon and starts effluent withdrawal. The supernatant is withdrawn until bottom water level (BWL) is reached; a few inches above the bottom lip of the decanter. At BWL, the vent valve is opened and air is once again introduced, stopping the decant. By breaking siphon a few inches above BWL, no scum (if any is present) can enter the decanter.

  • No floating, submerged moving or mechanical parts to malfunction, freeze, or require maintenance.
  • Fixed to the wall for easy installation and maintenance. All work can be done outside the tank.
  • Allows for more lineal feet of decanter, reducing the withdrawal velocity
  • Stops decanting at actual BWL. Floating decanters actually remove water at 18” to 24” below the water surface. Therefore at BWL, they are actually drawing water 18” to 24” deeper in the tank and therefore closer to the sludge blanket level.
  • Air filled at all times except for decant. Therefore no solids can accumulate in the decanter at the beginning or end of decant.
  • Requires no submerged valves to operate.
  • Requires less head to operate. Floating decanters require significant head to properly operate.
  • Does not require submerged swivel joints or hoses that can fail and require maintenance.