Define the Types of Sedimentation

1. Type I

• Particles that settle discretely (settle as individual particles)
• sand, grit
• Pre-sedimentation for sand prior to coagulation

2. Type II

• Particles that flocculate during sedimentation
• Size constantly changing, thus settling velocity
• Generally settling velocity increasing
• Alum or Iron coagulation, in primary sedimentation

3. Type III or zone sedimentation

• Particles or at high conc. (>1000 mg/l)
• Particle settle as a mass and a distinct clear zone and sludge zone are present
• Lime softening sedimentation, activated sludge sedimentation and sludge thickeners