Tennessee Wastewater Operator Practice Exam

What is the primary reason for mixing the contents of a primary digester?

1. To enhance oxygen levels in the tank

2. To distribute food evenly in the tank

3. To reduce odor in the digester

4. To increase the temperature of the contents

The correct answer is: To distribute food evenly in the tank

Mixing the contents of a primary digester is essential for ensuring even distribution of food throughout the tank. This uniform distribution allows the microorganisms responsible for anaerobic digestion to access the organic matter more effectively, promoting faster and more efficient breakdown of the waste. When the food is evenly spread, it helps maintain optimal conditions for microbial activity, which in turn enhances the overall performance of the digestion process. In this context, other options may address important aspects of digester management but do not capture the primary purpose of mixing. While increasing oxygen levels or temperature might be beneficial in certain processes, anaerobic digestion specifically operates without oxygen. Reducing odors can occur as a result of effective digestion, but it is not the primary goal of mixing the digester contents. Therefore, distributing food evenly represents the central intent behind mixing, making it the correct answer.