RotoFin Biological Contractors

RotoFin Biological Contractors


Roto Fin Biological Contractors (RFBC) is a patented and improved version of conventional Rotating Biological Contractor (RBC) systems. RBC system is a naturally aerated system where the rotating contractor is a drum filled with media for bacterial attachment. The ‘drum’ rotates slowly and is submerged partly in wastewater. As the drum rotates microbes absorbs the oxygen from the atmosphere.

Current RBC systems use narrowly packed sheet discs as media to provide enhanced surface area. The best media configuration enhances the available surface to 60-80m2/m3 of drum volume for the bacterial growth. Despite the increase in surface area the systems lead to large sized drums that not only increase the cost of the system but also create operational problems. As a result the efficient RBC technology has been restricted to extremely small size packaged plants only.

Akin to the RBC, the RFBC has a rotating drum but consisting of ‘pseudo rods’ with large number of Roto Fins on the periphery. The Roto Fin arrangement provides large surface area up to 240m2/m3 of the drum volume. The hollow structure of the ‘pseudo rod’ allows traverse movement of water in directions a feature which will help in better mixing of wastewater and oxygen inside the reactor. Moreover the ‘shaft torque’ energy is greatly reduced to save energy.

The system is generally aerobic and there is some facultative bacteria growth as well. As drum slowly submerges inside the effluent, active biomass attaches on to the media, stabilizing the dissolved organic matter in the wastewater

As the drum moves upward, the system absorbs the oxygen from the atmosphere. This is a continuous phenomenon as long as drum in rotation.

Similar to other attached growth process, sloughing off process is continuous and excess biomass is eliminated from the secondary settling unit. Generally no recirculation required with the system as huge quantity of sludge has already developed inside the media. Unlike other attached growth aerated process, RFBCs don’t require forced aeration or use of air blowers as oxygen is absorbed from the atmosphere itself.