Rotating Biological Contactors Information

Rotating biological contactorsRotating biological contactors are large discs on rotating shafts that are mounted in wastewater tanks, but only partly submerged. As the discs turn, the microorganisms on them repeatedly contact both air and the organic substances in the water.


A rotating biological contactor can be used where wastewater is amenable to biological treatment. Rotating biological contactors can be used in many ways to accomplish varied degrees of carbonaceous or nitrogenous oxygen demand reductions. Rotating biological contactors are fixed-film reactors similar to biofilters in that organisms are attached to support media. The support media are the slowly rotating discs that are partially submerged in flowing wastewater in the reactor. A rotating disc's contactor is an agitated column extractor that can carry out liquid-to-liquid extraction processes. The rotating disc contactor (RDC) is a vertical column, consisting of a series of compartments formed by stator rings. In the middle of each compartment, a central shaft drives a rotor ring.


The proper selection of a wastewater treatment product involves the identification of a rotating biological disc supplier that has both theoretical and practical knowledge of designing wastewater treatment systems. Secondary treatment is a biological treatment process to remove dissolved organic matter from wastewater. One of the approaches used to accomplish secondary treatment is the use of fixed film systems. Fixed film systems grow microorganisms on substrates such as rocks, sand, or plastic. Examples of fixed film systems include:

  • trickling filters
  • rotating biological contactors
  • sand filters

Immersed biological rotating discs that are mounted vertically on a horizontal rotating stainless steel shaft are used in the biological purification of sewage water.

The operation of rotating biological contactors is based on contactor rotating discs placed on a shaft that allows the discs to be partly submerged in effluent and support the biofilm responsible for the degradation of the organic compounds in the effluent. The efficiency of rotating biological contactors depends heavily on parameters such as hydraulic retention time, rotating biological disc speed, disc submergence, and the composition of the discs.

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