Tennessee Wastewater Operator Practice Exam

What percentage of a rotating biological contactor (RBC) is typically submerged during standard operations?

1. 20%

2. 30%

3. 40%

4. 50%

The correct answer is: 40%

In standard operations, a rotating biological contactor (RBC) typically has about 40% of its discs submerged in the wastewater. This level of submersion is crucial for several reasons. Firstly, being partially submerged allows the biofilm on the discs to be in contact with both the wastewater and the air. This exposure enables aerobic microorganisms to efficiently break down organic matter while also ensuring that the RBC operates effectively in terms of aeration and nutrient removal. Maintaining about 40% submersion optimizes the oxygen transfer rate and enhances the overall treatment performance by promoting the growth of beneficial bacteria that help degrade pollutants. Additionally, this design minimizes the risk of anaerobic conditions, which can lead to foul odors and reduced treatment efficiency. Understanding the operational parameters of an RBC is vital for effectively managing wastewater treatment processes and ensuring compliance with environmental regulations. This knowledge supports operators in troubleshooting issues and optimizing system performance.