Tennessee Wastewater Operator Practice Exam

What is the most important purpose of an anaerobic digester cover?

1. Keeping temperature stable

2. Minimizing odor emissions

3. Keeping oxygen out of the tank

4. Ensuring gas retention

The correct answer is: Keeping oxygen out of the tank

An anaerobic digester cover serves several critical functions, but keeping oxygen out of the tank is particularly paramount because anaerobic digestion relies on the absence of oxygen to promote the growth of anaerobic bacteria. These microorganisms break down organic material without oxygen, producing biogas as a byproduct. If oxygen were to enter the system, it could disrupt the anaerobic conditions necessary for these bacteria to thrive, leading to decreased efficiency in the digestion process and potentially producing harmful byproducts. While the other functions, such as minimizing odor emissions and ensuring gas retention, are also important, their effectiveness hinges on the primary function of maintaining anaerobic conditions. The retention of temperature and retention of biogas are secondary benefits that occur as a result of the anaerobic environment being sustained. Therefore, the most critical role of an anaerobic digester cover is to ensure that oxygen remains excluded, thereby supporting the optimal operation of the digestion process and maximizing biogas production.