In order to clarify or thicken a liquid, solid particulates or suspended solids are typically removed using a clarifier. Wherever the concentration of suspended solids in raw or wastewater is higher, clarifiers are necessary. Sedimentation tanks in almost all treatment plants. Clarifiers are circular in shape, and occasionally rectangular in shape. The process of sedimentation is the part of water & wastewater treatment where contaminants are settled down due to gravity and the clean liquid or clarified water is separated. The same principle of gravity settling is used by clarifiers in wastewater treatment to remove suspended solids or solid particulates from the liquid. The concentrated impurities are known as sludge whereas those that float to the surface of the liquid are called scum. The large settling tanks with in-built mechanical means like scraper blades act continuously to remove solids towards the pipe or place where sludge and scum collection takes place. The removed sludge will either be recycled as RAS (return-activated sludge) or wasted as WAS (waste-activated sludge). The clarified water is released over overflow weirs on the top of the clarifier which looks very clear.