Tennessee Wastewater Operator Practice Exam

What process is essential to control biogas quality in an anaerobic digester?

1. Regular feeding schedule

2. Adjusting temperature settings

3. Implementation of effective mixing

4. Maintaining sludge retention time

The correct answer is: Implementation of effective mixing

Controlling biogas quality in an anaerobic digester is critically linked to the implementation of effective mixing. Proper mixing ensures that the substrate (organic materials) is evenly distributed throughout the digester. This helps maintain a uniform environment that supports microbial activity, allowing for optimal digestion and biogas production. Mixing is essential for several reasons. It helps in preventing the formation of scum layers, which can impede gas flow and reduce the efficiency of gas collection. Additionally, effective mixing promotes contact between the microbes and the organic matter, enhancing the breakdown of solids and facilitating the release of biogas. This can impact not only the quantity but also the quality of the biogas produced, as it reduces the likelihood of undesirable byproducts. While other factors, such as a regular feeding schedule, temperature settings, and maintaining sludge retention time, are important for the overall operation of the anaerobic digestion process, they do not directly influence the microbial interactions and mixing environment as effectively as proper mixing does.