Types of Settling in Waste Water Treatment Plants

Following are the types of settling:
Type I Settling
Discrete, non-flocculent particles in a dilute suspension - settle as separate units, and there is no apparent flocculation or interaction between the particles - settling of sand particles in grit chambers
Type II Settling
Settling of flocculent particles in a dilute suspension - flocculate during settling and increase in size and settle at a faster velocity - settling in primary clarifiers
Type III Settling
Zone or hindered settling - settling in an intermediate concentration - the particles are so close together that interparticle forces hinder the settling of neighboring particles - settle at a constant velocity - settling in secondary clarifiers (upper part).
Also See: Hospital Waste
Type IV Settling
Compression settling - settling in a high concentration - the particles touch each other and settling can occur only by compression of the compacting mass - settling in secondary clarifiers (lower part)