3.1 Mechanisms of particle-removal (Suspended solids)
The main mechanisms of particle-removal are as follows
(1) Straining : Particles larger than the pore spaces of the sand medium are strained out mechanically and Particles smaller than the pore space are trapped within the filter by chance contact.
(2) Interception : Many particles that move along in the streamline are removed when they come in contact with the surface of the sand medium.
(3) Flocculation : Large particles overtake smaller particles, join them, and form still larger particles.
These particles are then removed by one or more of the above removal mechanisms.
(4) Sedimentation : Particles settle on the sand medium within the filter.