Abstract: A wastewater treatment apparatus is disclosed in which a rotating biological contactor rotatably mounted on a horizontal shaft is deeply submerged in a wastewater tank, so that a substantial portion of attached biomass does not come into contact with the ambient air. A plurality of gas conduits are disposed in the tank beneath the rotating contactor and are positioned to provide rotational energy to the contactor, to serve as the principal source of oxygen for the submerged biomass and to regulate the rotational velocity of the biological contactor so that the oxygen containing air bubbles are caused to rise into the central region of media rather than being swept along and confined to the outer radius of the media as it rotates.

Abstract: A method and apparatus for increasing the capacity of an activated sludge wastewater treatment plant which utilizes microscreens in conjunction with rotating biological contactors that are placed in the primary settling tank, the aeration tank and the final clarification tank. A rotatable microscreen is placed upstream of the primary settling tank and downstream of the final clarification tank. The result is a more efficient and less energy consuming system which reduces the organic loads. Preferably, the microscreening preceding the biological treatment stage will have a mesh size in the range of about 50-200 mesh and the microscreen placed after the biological treatment stage will have a mesh size in the range of 6-44 microns. Additional benefits are obtained in recycling the treated water which is passed through the rotating biological contactor as well as utilizing it to aid in rotating the contactor.