Settling basins and clarifiers are designed to retain water so that suspended solids can settle. By sedimentation principles, the suitable treatment technologies should be chosen depending on the specific gravity, size and shear resistance of particles. Depending on the size and density of particles, and physical properties of the solids, there are four types of sedimentation processes:
* Type 1 – Dilutes, non-flocculent, free-settling (every particle settles independently.)
* Type 2 – Dilute, flocculent (particles can flocculate as they settle).
* Type 3 – Concentrated suspensions, zone settling, hindered settling (sludge thickening).
* Type 4 – Concentrated suspensions, compression (sludge thickening).
Different factors control the sedimentation rate in each.