California Wastewater Treatment Operator Practice Exam

What happens during the sedimentation process in a clarifier?

1. Solid particles rise to the surface

2. Liquid waste is evaporated

3. Solids settle to the bottom

4. Gas is released from the water

The correct answer is: Solids settle to the bottom

During the sedimentation process in a clarifier, solids in the wastewater are allowed to settle to the bottom due to gravity. The purpose of this process is to remove suspended solids from the liquid waste, allowing the clearer liquid to remain at the top while the heavier solid particles accumulate at the bottom as sludge. This separation is critical in wastewater treatment as it helps in achieving a cleaner effluent that undergoes further treatment stages. The settling process occurs as the flow of wastewater enters the clarifier, where the reduced velocity allows the solids to descend. Factors such as particle size, shape, and density influence the settling rate, making it a crucial step in the overall treatment process. The clarified liquid can then be removed from the top of the clarifier for further treatment or discharge, while the accumulated solids can be collected and processed appropriately. This effectiveness of sedimentation emphasizes its importance in the reduction of turbidity and solids load in wastewater treatment systems.