Tennessee Wastewater Operator Practice Exam

What might prompt an operator to increase the RAS flow rate after inspecting the activated sludge process?

1. Sludge blanket depth under 1 ft

2. Clarifier blankets deeper than 2 ft

3. Visible foam at the surface

4. Increased pH levels

The correct answer is: Clarifier blankets deeper than 2 ft

Increasing the return activated sludge (RAS) flow rate can be essential for maintaining optimal conditions in the activated sludge process. When the clarifier blankets are deeper than 2 ft, it suggests that there is excessive sludge accumulation. A deeper sludge blanket can lead to poor settling characteristics, potentially causing effluent quality issues due to the carryover of solids. In this scenario, increasing the RAS flow rate helps to remove the excess sludge from the clarifiers, thus reducing the sludge blanket depth. This action contributes to improved settling and solids management, thereby enhancing the overall efficiency and performance of the activated sludge system. Additionally, it ensures that the remaining solids in the system are within the desired concentration range, promoting effective microbial activity and nutrient removal. The other options are linked to different conditions requiring distinct operational adjustments, making them less relevant for prompting an increase in RAS flow specifically in regard to clarifier performance and sludge management.