| Process | Description |
| (i) Straining | P: Removes only particles in the water large enough to get caught in the pores of the filter |
| (ii) Sedimentation | Q: Larger and heavier particles do not follow the fluid streamline around the sand grain and settle on the grain |
| (iii) Interception | R: Particles that do follow the streamline, but are too large and are caught because they brush up against the sand grains |
| (iv) Diffusion | S: Very small particles are experiencing Brownian motion and may collide with the sand grains by chance |