# Advantages of Different Lamella Clarifier Designs

Allen Hazen defined in 1904 the law for sedimentation:

Vs – settling velocity of a particle divided by settling height – has to be bigger as – Water flow Q divided by tank volume.

Applied to a lamella clarifier this means that a particle is only settled down when the settling velocity of the particle divided by channel height, is bigger than the water velocity divided by the channel volume.

Vs of the particle must be bigger than the upward stream Q.

Case 1: Vs divided by H is bigger as Flow Q divided by channel volume. The particle can be settled down.

Case 2: Vs divided by H is smaller as Flow Q divided by channel volume. The particle cannot be settled down.

When the channel distance of the plates is equal, H can be crossed out of the equation. Then L multiplied W projects the surface area of the lamella clarifier module in the horizontal direction.