An apparatus for aerobic biological treatment of waste water and the like includes a tank configured to retain waste water therein, and a wheel rotatably mounted in the tank. The wheel includes a plurality of chambers arranged in axial succession about the circumference of the wheel. The chambers include openings which are oriented generally upwardly and emerge from the waste water adjacent a top dead center position of the wheel and are oriented generally downwardly and submerged in the waste water adjacent a bottom dead center position of the wheel. An air drive mechanism rotates the wheel, and an air pipe communicates with the air drive mechanism, and is disposed generally below the wheel, and is configured to release air bubbles therefrom after the bottom dead center position. A plurality of bubble connectors are connected with and protrude radially outwardly from the wheel at locations preceding the openings, and are shaped to guide the bubbles from the air pipe through the openings into the chambers.