Abstract: A method and apparatus for purifying industrial waste fluids by an aerobic biological treatment is provided herein, which is capable of concurrently purifying waste gases emanating from such waste liquids. The improvement relates to the elimination or reduction of odors and volatile organic substances by enclosing all tanks and basins from the influent of the waste water treatment plant up to the aeration treatment zone for the liquid waste water and venting these gases to an aerobic digester and/or an aeration basin to biologically decompose or degrade the VOS in the waste gas by action of the microorganisms in the aeration basin or aerobic digester.