ABSTRACT
The rotating biological contactor (RBC) is a variation of the attached growth idea provided by the trickling filter (see Figure 5.1). Still relying on microorganisms that grow on the surface of a medium, the RBC is instead a fixed-film biological treatment device. The basic biological process, however, is similar to that occurring in trickling filters. An RBC consists of a series of circular plastic disks mounted side by side and closely spaced; they are typically about 11.5 ft in diameter (see Figure 5.2). Attached to a rotating horizontal shaft, approximately 40% of each disk is submerged in a tank that contains the wastewater to be treated. As the RBC rotates, the attached biomass film (zoogleal slime) that grows on the surface of the disks moves into and out of the wastewater. While submerged in the wastewater, the microorganisms absorb organics; when they are rotated out of the wastewater, they are supplied with needed oxygen for aerobic decomposition. As the zoogleal slime reenters the wastewater, excess solids and waste products are stripped off the media as sloughings. These sloughings are transported with the wastewater flow to a settling tank for removal.
