John Meunier SAM® GFW Grit Washer with Shaftless Screw

Source: Veolia Water Technologies


GFW Grit Washers offer a solution to separate, wash and dewater grit to protect downstream processes and improve their performance. It consists of a conical hopper set on top of a shaftless spiral screw conveyor.


  • The grit mixture is fed at the top of the hopper, close to the periphery where a slow coerced rotational movement is induced. This swirl movement combined with the retention time enhances the settling of particles.
  • Up to 95 % removal efficiency of grit sizes ranging between 70 mesh and 60 mesh (200 μm and 250 μm) can be obtained.
  • Wash water injected at the bottom of the unit with the action of a central stirrer located in the accumulated grit area, scours the settled material. The flow velocity within the hopper maintains in suspension the organic matter that has been scoured and washed off the grit particles’ surface. The organic matter is discharged from the hopper at adjustable intervals. It can either be returned to the plant influent flow or onward to secondary treatment.
  • Up to 97 % of organic matter reduction and up to 90% grit dewatering can be obtained.
  • The settled grit is dewatered by the up lift motion of the screw then discharged at the top portion of the conveyor at adjustable intervals.
  • A continuous bagging system can be fitted to the screw discharge, to provide a totally enclosed system that will enhance odor control. The bag also eliminates possible physical contact with the sealed grit.