Tennessee Wastewater Operator Practice Exam

What controls the rotating speed of an air-driven rotating biological contactor?

1. Water pressure

2. Temperature variations

3. Aeration rate

4. Biomass concentration

The correct answer is: Aeration rate

The rotating speed of an air-driven rotating biological contactor (RBC) is primarily controlled by the aeration rate. In an RBC system, the aeration rate influences the rotational speed because it affects the amount of air being supplied and the level of oxygen dissolved in the water, which is crucial for the microbial activity necessary for wastewater treatment. A higher aeration rate typically encourages better microbial growth on the media and can lead to a faster rotation to enhance the contact of the biofilm with the wastewater. Conversely, if the aeration is reduced, the speed might also decrease to maintain optimal conditions for treatment and prevent overloading the biomass. While water pressure, temperature variations, and biomass concentration can impact the operation of the RCB, they do not directly control the rotational speed in the way that aeration rate does. The aeration rate is specifically designed to optimize the treatment process by ensuring that sufficient oxygen is available for the biofilm, thus directly affecting how quickly the biological contactor rotates to maximize efficiency in wastewater processing.