Large particles may be removed from water by settling (gravity force) their mass overcomes fluid forces
Fine colloidal particles do not settle due to gravity quickly enough insufficient mass to overcome fluid forces
eg. clay, salt, mineral oxides, usually < 10 μm
Coagulation
Combines small particles into large aggregates
- Coagulant formation
- Particle destabilisation
- inter-particle collisions
Flocculation
- gentle mixing of stabilized colloids to speed agglomeration
- forms flocs