Treatment of Municipal Wastewater by using Rotating Biological Contractors (Rbc’s)

The rotating biological contactor process offers the specific advantages of a biofilm system in treatment of wastewater for removal of soluble organic substances. It is a unique adaptation of the movingmedium biofilm system which facilitates easy and effective oxygen transfer. Media in the form of several large flat or corrugated discs with biofilm attached to the surface is mounted on a common shaft partially submerged in the wastewater and rotated through contoured tanks in which wastewater flows on a continuous basis. The compactness of the system and its economical operation makes it a viable option specially suited for decentralized wastewater treatment technologies. The process optimisation and adaptability under different environmental conditions and influent characteristics remain challenging tasks for the efficient use of this technology. Oxygen is accepted to be one of the most important and often limiting substrates in an aerobic treatment process. Oxygen transfer through the water film developed on a rotating disc revealed that the oxygen transfer coefficient varies with the rotational speed and the location on the exposed disc surface. Increase of ambient temperature resulted in decrease of the oxygen mass transfer rate. The biofilm model was implemented for a three stage rotating biological contactor based on a laboratory-scale experimental set-up. The process kinetics was adopted from the Activated Sludge which represents a mixed culture biomass environment.