Sedimentation can also occur as part of the pre-treatment process, where it is known as presedimentation. Presedimentation can also be called plain sedimentation because the process depends merely on gravity and includes no coagulation and flocculation. Without coagulation/flocculation, plain sedimentation can remove only coarse suspended matter (such as grit) which will settle rapidly out of the water without the addition of chemicals. This type of sedimentation typically takes place in a reservoir, grit basin, debris dam, or sand trap at the beginning of the treatment process.
