Tennessee Wastewater Operator Practice Exam

How does air transfer efficiency improve after cleaning?

1. Increased air pressure

2. Reduction of bubble size and faster rise rates

3. Smaller bubble size and slower rise rates

4. Less water flow required

The correct answer is: Smaller bubble size and slower rise rates

The correct choice emphasizes that after cleaning, the efficiency of air transfer in wastewater treatment systems improves through the generation of smaller bubble sizes and slower rise rates. When bubble size is reduced, the surface area exposed to the wastewater increases, which enhances the mass transfer of oxygen from the bubbles into the water. Smaller bubbles have a larger surface area relative to their volume compared to larger bubbles, making it easier for oxygen to dissolve into the wastewater. Additionally, while larger bubbles tend to rise quickly, smaller bubbles rise more slowly, allowing them longer contact time with the water, which facilitates further oxygen transfer. This principle is essential in practices for optimizing aeration efficiency in wastewater treatment. If bubbles were larger and rose too quickly, they would not have sufficient time to transfer oxygen to the water, leading to inefficient aeration and potentially inadequate treatment of the wastewater. By focusing on achieving smaller bubble sizes through cleaning processes, operators can significantly enhance the performance of the aeration system, thus ensuring effective treatment and better water quality outcomes.