The dewatering screw is specially designed to, by means sedimentation, obtain a separation between a liquid and solid (sand) particles. The liquid flows over the rim of the screw while the solid particles sink downward. The sunken particles are then brought up by the screw. The result is a robust design with a minimum of moving parts. This has the advantage of low maintenance costs combined with high reliability.
The water with the solid particles is introduced at the top of the deep end of dewatering screw. Because of the large surface area the particles slowly sink to the bottom. Because of the large surface area the particles sinking slowly out to the bottom. The overflow is in the narrowed part, it is provided with removable height plates to set the level. The sedimented material is transported from the settling tank by the screw. The length of the screw provides an additional dewatering.