Abstract: A method of recycling the off gas from an ozone disinfection step used with an activated sludge waste water treatment system, and apparatus for carrying out the method. The moisture is removed from a substantial portion but not all of the ozonation off gas, while the nitrogen and carbon dioxide contaminants that are contained in the off gas are left in it. The dried off gas is mixed with oxygen enriched gas from the original source, and the resulting mixture is delivered to the ozone generator for the production of more ozone. Another portion of the ozonation off gas is diverted upstream for introduction into the oxygen treatment facility of the activated sludge treatment plant. The drying of the ozonation off gas is preferably carried out by use of a two cycle self-purging dryer, with the portion of the ozonation off gas that is not delivered as a recycle component to the ozone generator utilized as the purge gas for the dryer before it is recycled upstream.

Abstract: A rotating gas diffuser for shearing fine gas bubbles from the surface thereof when the diffuser is immersed in a body of liquid and rotated therein. The rotatable shaft of the diffuser may carry a plurality of main rigid structural spokes and an equal number of rigid hollow gas feed conduits positioned alternately around the shaft. A plurality of plates, each in the form of a section of an annulus with its lateral edges radially positioned with respect to the circular rotating gas diffuser, is supported either on the top or the bottom of the diffuser, or on both, near its perimeter. Each porous plate is carried by a plate holder that has a shape similar to its associated porous plates, and with those plates defines a gas plenum having an area substantially equal in extent to, but no greater than, the area of the plates.