In the condensation mechanism, air in excess of atmospheric saturation comes out of solution by formation on the surface of the suspended particle. This is not the dominant mechanism, however, since non-turbulent depressurization of the suspension results in a degree of super saturation. Hence, it is necessary to first achieve near complete air release by turbulence before attachment to the particles. The collision mechanism is perhaps the most significant in the flotation process. Air bubble and particle size must be controlled to some extent to ensure that there is a sufficient radius of attachment to maintain the bond until separation.
Particle size is controlled by the amount of chemical added during the enflocculation process.
This occurs as the air bubbles become embedded in the floc mass. Rise rate of the undisturbed agglomerate is governed by Stokes' Law. The flotation process is employed where separation of particles having specific gravities close to that of water is desired. The flotation process will provide faster separation and higher ultimate solids concentration. The retention tank is a pressure vessel designed to provide sufficient time for dissolution of air into the stream to be treated.