Texas Wastewater Class B Practice Exam

What role do surface scrapers play in clarifier operation?

1. They circulate the water in the tank

2. They remove odors from the water

3. They help to remove scum from the surface

4. They add chemicals to the water

The correct answer is: They help to remove scum from the surface

Surface scrapers are specifically designed to help remove scum from the surface of the clarifier. Scum typically consists of floating materials such as oils, greases, and other light solids that can accumulate on the water's surface due to processes within the wastewater treatment. By effectively removing this scum, surface scrapers ensure that the clarifier operates efficiently and enhances the overall treatment process. The role of surface scrapers is critical because if scum is allowed to build up, it can interfere with the treatment process by impacting the settling of solids below and potentially releasing odors or contaminants back into the water being treated. Therefore, their presence assists in maintaining water quality and operational efficiency in the clarifier. Other options, though related to wastewater treatment, pertain to different functions that are not relevant to the primary objective of surface scrapers. For instance, the idea of circulating water is a function typically associated with mixing devices, while odor removal is managed through other treatment methods and processes. The application of chemicals is also outside the scope of surface scrapers, as that involves separate systems for chemical addition to aid in coagulation or disinfection processes.