How many stages are typically present in the rotating biological contactor process?

The correct answer is that the rotating biological contactor (RBC) process typically consists of four stages. This treatment method effectively uses a series of rotating discs or plastic media that are partially submerged in the wastewater.

In an RBC system, the stages can be thought of in terms of the various processes involved: the initial stage often involves the growth of biofilms on the media as microorganisms attach to the discs. In the subsequent stages, there is a combination of biological treatment, where these microorganisms break down organic matter, and the aeration process, which enhances oxygen transfer to support biological activity. Lastly, clarifying stages ensure that the treated effluent is separated from the biomass before discharge.

The four-stage setup is designed to optimize treatment efficiency and ensure adequate residence time for biological reactions to occur. Adding more stages can complicate the design and operation, while fewer stages may not provide sufficient treatment effectiveness, which is why four stages are standard in most configurations of the RBC process.