Tennessee Wastewater Operator Practice Exam

How is air excluded from a floating cover digester?

1. By using a water seal at the bottom of the skirt

2. By maintaining high pressure inside the chamber

3. By employing gas vacuums

4. Through a solid top cover

The correct answer is: By using a water seal at the bottom of the skirt

A floating cover digester is designed to minimize air exposure, which is crucial for anaerobic digestion processes requiring an oxygen-free environment. The method of using a water seal at the bottom of the skirt is effective because it creates a barrier that prevents air from entering the digester. This seal maintains the anaerobic conditions needed for bacteria to thrive and break down organic matter without oxygen interference. The water serves as a physical barrier, ensuring that any air is kept out effectively. While maintaining high pressure inside the chamber might also contribute to keeping air out, it does not function as the primary mechanism like a water seal does. Gas vacuums may be used in some systems, but they are typically more about gas collection rather than air exclusion. Similarly, a solid top cover does help in reducing air exposure, but the water seal is a more specific and effective method for ensuring anaerobic conditions in a floating cover digester.