Tennessee Wastewater Operator Practice Exam

Which example describes a fixed film treatment process?

1. SBR

2. Nutrient removal system

3. RBC

4. Aerated lagoon

The correct answer is: RBC

A fixed film treatment process is characterized by the presence of a stationary biomass that attaches to a solid structure, where microbial activity occurs on the surface of that fixed medium. In this context, the correct answer refers to a Rotating Biological Contactor (RBC), which is a type of biological treatment system. In an RBC, plastic media are arranged on rotating discs that are partially submerged in the wastewater. Microorganisms adhere to the surfaces of these discs, forming a biofilm. As the discs rotate, they alternate between being submerged in the wastewater and exposed to the air, providing optimal conditions for the biofilm to treat the wastewater effectively. This process relies on the fixed biomass on the discs to facilitate biological treatment of the organic matter in the wastewater. The other options describe various types of treatment processes that do not rely predominantly on fixed film structures. A Sequencing Batch Reactor (SBR) operates in batch mode and relies on suspended biomass rather than fixed biomass. A nutrient removal system may involve multiple treatment methods, typically focusing on nutrient removal rather than a specific fixed film application. An aerated lagoon uses a different method of treatment that involves suspended growth systems rather than a fixed film, utilizing aeration to support microbial activity in a lagoons setting.