Wastewater New York State Practice Exam

What is the role of the agitators in an anaerobic digester?

1. To cool the mixture

2. To enhance sedimentation

3. To keep solids suspended and in contact with bacteria

4. To remove excess biogas

The correct answer is: To keep solids suspended and in contact with bacteria

The correct choice highlights the critical function of agitators in an anaerobic digester, which is to keep solids suspended and maintain their contact with bacteria. In the anaerobic digestion process, microorganisms break down organic matter in the absence of oxygen, generating biogas as a byproduct. For efficient digestion, it's essential that the solid waste material remains mixed throughout the digester. This mixing ensures that all solid particles are evenly distributed and come into contact with the bacteria responsible for decomposition. If solids settle at the bottom or float, parts of the substrate may not be adequately treated, leading to inefficiencies in biogas production and potential operational issues within the digesting system. Therefore, agitators play a vital role in promoting the contact between solids and bacteria, enhancing the overall efficiency of the anaerobic digestion process and optimizing biogas yields.