The method of treatment of a body or bodies of liquid, that is essentially aqueous, and containing other components, the method including introducing O₂ molecules into said liquid body or bodies to increase dispersed or dissolved oxygen content of the liquid, and allowing at least some of the dispersed or dissolved O₂ to sink in the body of liquid for retention and treatment of said other components. A submerged venturi is preferably used to entrain air in a stream of such liquid, sub-micron oxygen being formed and dispersed.