Tennessee Wastewater Operator Practice Exam

Why must air supply to an aeration tank be adequate?

1. To maintain D.O. at the center of the floc

2. To prevent odorous conditions

3. To facilitate rapid settling

4. To reduce the sludge bulking

The correct answer is: To maintain D.O. at the center of the floc

An adequate air supply to an aeration tank is crucial because it ensures that dissolved oxygen (D.O.) levels remain high enough to support the process of aerobic digestion, which is essential for the breakdown of organic matter in wastewater. The microorganisms responsible for this digestion require oxygen to thrive, and this oxygen is often supplied through aeration. Maintaining D.O. at the center of the floc is particularly important because the microorganisms live in clusters known as floc. If D.O. levels drop too low, the aerobic microorganisms can become stressed, leading to ineffective digestion and potentially causing the floc to break down. This could result in pollutants not being adequately removed from the wastewater, which would compromise the treatment process. While preventing odorous conditions and reducing sludge bulking are significant aspects of wastewater treatment, they are often secondary benefits that stem from maintaining adequate D.O. levels. If the oxygen levels are not sufficient, the system may become anaerobic, which can lead to the production of foul odors and other operational issues. However, the primary reason for adequate air supply is to ensure sufficient oxygen for the microorganisms, thus playing a central role in the biological treatment of wastewater.