ROTATING BIOLOGICAL CONTACTOR (RBC)

Rotating biological contactors (RBC) were developed during the early 1970's, the process generally based on technology originally described in 1925. With a rotating biological contactor the biological film (the equivalent of the biomass found in an activated sludge plant) is supported on a medium that rotates in a horizontal plane and is partially immersed in a trough through which settled sewage flows.

The medium is usually manufactured from plastic in the form of discs (up to four metres diameter) mounted on a central shaft and the discs are usually corrugated to increase the available surface area. As the medium is only partially submerged and therefore the biomass will be subject to periodical removal from the wastewater flow, the oxygen required to permit respiration is extracted from atmospheric air.

Excess biomass (the equivalent of surplus sludge in an activated sludge plant) is continually sloughed from the support medium and treated effluent must therefore always discharge to a secondary clarifier to settle entrained solids prior to the discharge of final effluent from the plant.

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