How does sedimentation occur in water treatment?

Sedimentation in water treatment refers to the process where larger particles or solids settle out of the water due to the force of gravity. This is a natural and efficient way to clarify water by allowing heavier particles to sink to the bottom of a tank or basin after a period of time. In this method, water is typically held still, or in quiescent conditions, enabling the suspended solids to separate from the water column without the influence of turbulent flows.

In contrast to filtration, where particles are physically removed by passing water through a porous medium, sedimentation relies on the natural settling characteristic of particles. Pumping water at high velocities can disrupt the settling process by keeping solids suspended in the water. While the addition of coagulants can help in binding smaller particles together to form larger aggregates (or flocs) that can then settle out, sedimentation itself specifically focuses on the gravitational settling of these solids once they have coagulated.