Tennessee Wastewater Operator Practice Exam

An RBC that is lightly loaded may effectively remove which substances?

1. BOD and TSS

2. BOD and NH3N

3. TSS and Phosphorus

4. NH3N and Pathogens

The correct answer is: BOD and NH3N

A rotating biological contactor (RBC) is a type of wastewater treatment technology that utilizes microbial growth on rotating discs to treat wastewater. When an RBC is lightly loaded, it means that the concentration of organic matter and other substances entering the system is relatively low. This condition can significantly affect the performance of the RBC in terms of its ability to remove various contaminants from wastewater. The removal of biological oxygen demand (BOD) and ammonia nitrogen (NH3N) is particularly effective when the RBC is lightly loaded. BOD is a measure of the organic pollution in water; microorganisms in the RBC can metabolize this organic material, thereby reducing BOD levels as they thrive on the available nutrients. When the load is low, these microbes can be more effective at utilizing available substrates without being overwhelmed, leading to a higher percentage of BOD reduction. Similarly, NH3N refers to ammonia nitrogen, which is another significant component of wastewater, especially from human and industrial sources. Under the right conditions, the bacteria in the RBC can effectively convert ammonia to nitrite and nitrate through a process called nitrification. In lightly loaded conditions, there is insufficient competition for resources, allowing for more efficient conversion of ammonia. While other options include combinations of total suspended solids (T