Texas Wastewater Class B Practice Exam

If an operator notices dead spots in the aeration tank, what issue is likely occurring?

1. High dissolved oxygen

2. Plugged diffusers

3. Low sludge concentration

4. Insufficient aeration volume

The correct answer is: Plugged diffusers

Identifying dead spots in an aeration tank typically points to issues with the aeration system's ability to distribute air evenly throughout the tank. When diffusers become plugged, they fail to release air effectively into the water, leading to areas with inadequate mixing and aeration—these areas are referred to as dead spots. When diffusers are functioning properly, they facilitate an even distribution of air bubbles, which helps maintain uniform conditions necessary for the aerobic processes to occur. However, if the diffusers are compromised due to clogging, certain portions of the tank may not receive sufficient oxygen, affecting the overall treatment efficiency. Other options might suggest potential concerns within the aeration system, but they do not directly relate to the creation of dead spots in the same manner as plugged diffusers do. Thus, understanding the mechanics of aeration and the importance of diffuser function clearly highlights why recognizing plugged diffusers is crucial when dead spots are observed.