ABSTRACT
A Rotating Biological Contactor is a long shaft with disks of media mounted on it. The media disks are rotated through a tank of primary effluent. Since the disks are only about 40% submerged, the media con tacts both the soluble food for the growing bugs on the media and the air to give the bugs the oxygen they need. The media disks are typically 12 ft or 3.6 m in diameter and are mounted on a horizontal shaft generally 25 ft or 7.5 m long. A standard media shaft will provide about 100,000 ft2 or 9300 m2 of surface area for the slime mass of bugs to grow on. The media needs to be rotated at a particular speed. Typically, rotational speeds are in a range of 1.5 to 1.6 rpm. At rotational speeds outside this range the bugs lack the appropriate contact time with both the food and the oxygen. The biomass grows thicker as the bugs eat and reproduce. Eventually the thick biomass portion will hill off. Because of these “sloughings” the RBC must be followed by a settling tank to remove these solids from the treated wastewater.
