Sedimentation
Raw water contains various suspended matters such as reduced iron and manganese, bacteria and organic colloids as impurities. These can be allowed to settle and removed when the water stands still.
Actually sedimentation of these suspended particle§ start when they are stored in the reservoir itself Sometimes, as in the case of clarification of river water, sedimentation can be used without pre-treatment and is called plain sedimentation. In other cases pretreatment like aeration, coagulation and flocculation are required before sedimentation.
