Rotating Biological Contactor (RBC)

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Rotating biological contactor is a biological treatment process used to remove biodegradable, soluble, organic materials from sewage thereby achieving a high quality effluent. This process is used in the treatment of wastewater following primary treatment. Grits and other solids are removed in the primary treatment process through a screening process. It is followed by a period of settlement. This process allows the wastewater to come in contact with a biological medium to remove pollutants in the wastewater prior to the discharge of the treated wastewater to the environment.

Construction
Rotating biological contactor is a secondary treatment process. It is made of a series of closely spaced, parallel discs. The discs are mounted on a rotating shaft which is supported just above the surface of the waste water. The biological degradation of the wastewater pollutants takes place at the surface of the discs where microorganisms grow. The rotating packs of disks means the media are kept in a tank or trough. The most common used plastics for the media are PVC, expanded polystyrene, and polythene. The shaft is usually aligned with the flow of wastewater so that the discs rotate at 90° to the flow with several packs. It is mainly combined to make up a treatment train. Almost 40% of the disc area is immersed in the wastewater.

The membrane bio-reactor become active in the secondary stage. It provides better service and in a much smaller space. This MBR device is used for the biological oxidation of the organic material dissolved in sewage and the separation from the resultant slurry of a relatively clean liquid. The extra amount of solids created by the oxidation process is easily removed for subsequent treatment. It is a process that goes continuously, and can be controlled easily. It is becoming the best available technology for waste water treatment.

Factors Affecting the Performance of RBC
There are some major factors, which control the treatment performance of all rotating biological contactor systems.

• Influent wastewater characteristics
• Wastewater temperature
• Organic and hydraulic loading rates
• Dissolved oxygen level
• Flexibility in operation
• Biofilm control