pressure these two mechanical forces accelerate the mass transfer limited solublization of the water by air the next stage is the flow of the water air mixture over the series of sharp edges or ridges 52 incorporated into the upper surface of the plate portions 46 as the water air mixture flows over the sharp edges both turbulence and pressure fluctuations increase the mass transfer of air into water the next steps occur as the water is directed outwardly onto the screen 32 which surrounds the saturation column diffuser plate assembly 34 the water air mixtures leaves the outer edge of the plates with enough velocity to cover the inch or so space between the edge of the plate and the screen and strike the screen with considerable force these actions increase turbulence and shear and thus increase the exposed water surface to air interface which increases the transfer rate between air and water the next step includes two actions the first being the free fall of relatively small water droplets from the screen to the water level by controlling the level of the air water interface inside the vessel it is possible to change the level of saturation accomplished during this stage the small droplets fall through the air and are exposed to the air falling droplets of water take advantage of the high water surface area to air exposure this creates a relatively high transfer rate between the air and water as a side note it is possible to control this portion of the saturation process by changing the level of the water air interface thereby providing some flexibility in the saturation level during unit operation the second action is when the falling water hits the surface of the water inside the.