Method for improving bubble surface area exposure

A method for increasing bubble-production of gas bubbled upwardly through a first liquid composition consisting essentially of a major amount of water relative to lesser total amounts of other liquids and solids within a container vessel in an amount sufficient to permit upward movement of bubbles therethrough, the improvement consisting essentially of placing said liquid into said container vessel, thereafter placing at least two substantially horizontal first and second spaced-apart screens within the liquid at locations spaced a substantially large distance below an upper surface of the liquid sufficiently below said upper surface such that optimally a major amount of surface area contact is obtained by the composition with bubbles produced at said locations by a gas passed upwardly through the screens, placing the second screen at least about 1/2 inch for lower mesh size thereof down to about 1/4 inch for higher mesh size thereof above the first screen, utilizing as said first and second screens, screens each having mesh size within a range of from about 25.times.25 mesh to about 4.times.4 mesh, U.S. Standard Mesh, and bubbling the gas upwardly through the liquid composition from a plurality of gas outlets located within said container vessel below the first screen from a point within or below the liquid.