Flotation is usually used in applications where the solid or liquid particles either float naturally or are only slightly denser than water, such that gravity sedimentation is not effective or practical
Flotation is a unit operation used to remove solid or liquid particles from water. The untreated water is introduced into a basin, and gas (usually air) is added to facilitate separation of the material from the water. Rising gas bubbles adhere to or are trapped in the particle structure of the material, and the particles then rise to the surface, forming a floating layer which is removed by a surface skimming mechanism. Clarified liquid exits the tank from a point well below the surface. Chemical treatment, including coagulation and/or polymer flocculation, is often used as a pretreatment for flotation, to assist in the formation of a structured floc to which the gas bubbles can readily adhere.