When muddy water is made to stand still for some time, we can clearly observe three layers. One of water, second of mud, and third of muddy water?

Sedimentation is a process where a heavier component is separated out from the liquid by making the liquid stand still for some time, thereby leading the heavier particles to settle down.

When muddy water is made to stand still for some time, we can clearly observe two layers. One is of the mud that settles at the bottom and the other is of water above the settled layer of mud.