Florida Wastewater Practice Test

What is the primary purpose of a secondary clarifier in wastewater treatment?

1. To aerate the water

2. To separate solids from liquids

3. To add chemicals for treatment

4. To increase temperature

The correct answer is: To separate solids from liquids

The primary purpose of a secondary clarifier in wastewater treatment is to separate solids from liquids. In the context of the treatment process, the secondary clarifier acts as a settling tank where biological solids, also known as biomass or sludge, that have been generated during the biological treatment phase, can settle out from the treated effluent. After the biological treatment stage, where microorganisms break down organic matter, the water contains suspended solids and would need to undergo clarification. The secondary clarifier allows gravity to do the work of separation, as the heavier solids settle to the bottom, forming sludge, while the clearer liquid rises to the surface and can be decanted for further treatment or discharge. This process is crucial to achieving a high-quality effluent that adheres to environmental regulations before being released back into the environment or into further processing. Other processes, such as aeration, chemical addition, or temperature control, are important in various stages of wastewater treatment but are not the primary functions of a secondary clarifier.