Rotating Biological Contactors

Rotating biological contactors (RBCs) were originally developed in Europe and recently accepted by America and Asia. The process system, as shown in Fig. 1 is primarily a fixed-film biological reactor consisting of a synthetic medium mounted on a horizontal shaft and placed in a contour-bottomed tank. The general concept of rotating biological contactors is to let wastewater flow through the tank, and to rotate the medium in the wastewater to be treated, alternatively exposing the medium (and the attached biological growth) to air and the wastewater. The slowly rotated media are about 40% immersed in the wastewater for aerobic removal of organic waste by the biological film developing on the media. The lattice-structured medium, and to a lesser extent the disc structure, is fragile and should be protected from direct exposure to wind, sun, and weather fluctuation. Therefore, the media are usually enclosed in a superstructure or individual shaft covers.