RBCs are a fixed film, aerobic, biological wastewater treatment system. Physically, they consist of parallel, deformed discs mounted perpendicularly on a shaft that is slowly rotated in a tank through which the wastewater to be treated is passed. The shaft is mounted at or above the water level in the tank, so that less than half of the discs are submerged.

RBCs have also been used as an anaerobic process by submerging the media discs banks entirely in the tank.

During the aerobic treatment process, microbes that remove the organic material in the wastewater (by using the organic material as a food source) attach themselves to the media discs surfaces. They grow in a thin biofilm, whose thickness is controlled by the shearing force of the discs being rotated through the water. By rotating out of the water into the atmosphere, the microorganisms, growing on the media discs banks, are provided with oxygen. The surplus microorganisms that are sheared off the discs are carried with the wastewater to clarifiers where they are separated from the treated wastewater.

Microorganisms that remove carbonaceous material predominate until the soluble Biological Oxygen Demand (BOD) is reduced to below 10 mg/l when nitrifiers begin to flourish. The effluent quality is predictable using industry standard modeling equations.

The surface area available for biological growth is the primary determinant of the size of the RBCs relative to treatment performance. BMT offers the highest surface area to volume ratio of any RBC.

However, no matter how much surface area is provided, the microbes must be brought into intimate contact with the wastewater and the uptake of oxygen cannot exceed the transfer of oxygen. The critical factors in this regard are prevention of plugging of the discs with overgrowth of microbes and providing sufficient surface area and turbulence for oxygen transfer. The BMT’s design addresses both of these issues by providing the highest surface area to volume and a variable speed drive that allows changing the amount of turbulence and shearing force.