The objective of the sedimentation process, which is a physical treatment process, is to allow the settling out of particulate material in a reasonable amount of time. The sludge storage zone should be configured for the correct amount of accumulated sludge and to ensure efficient removal of sludge. The outlet zone should be designed to ensure uniform velocities across the cross section of the basin and to remove water from the basin without carrying away suspended particles.
Outlets are usually configured in a series of troughs, or weirs, that provide a large Ac.
Design of the settling zone depends on several sedimentation concepts. Since particle size changes with time and depth, velocity also changes. These results can be used to design a settling basin by preparing curves of R vs. detention time and R vs. overflow rate, and applying appropriate scale-up factors.