Tennessee Wastewater Operator Practice Exam

Which of the following components is included in the working volume of an anaerobic digester?

1. Influent water

2. Digesting solids

3. Rinse water

4. Thermal insulation

The correct answer is: Digesting solids

The working volume of an anaerobic digester primarily consists of the digesting solids, which are the organic materials that are being broken down by anaerobic bacteria during the digestion process. This component is critical to the function of the digester because it is the actual biomass and organic waste that undergoes microbial activity, ultimately leading to the production of biogas and digestate. Digesting solids contribute to the overall volume that is actively involved in the digestion process. These solids include a mixture of organic waste and any additional substrates added to enhance the digestion process. The dynamics of microbial processes, such as the conversion of organic materials into methane and carbon dioxide, occur within this volume, which is fundamental to the operational efficiency of the digester. In contrast, influent water plays a role in transporting materials into the system but is not a direct component of the digestion process since it mainly acts as a carrier. Rinse water, often used for cleaning or maintaining equipment, is not involved in the digestion process either, and thermal insulation, while essential for maintaining temperature and efficiency in the digester, does not contribute to the working volume where microbial action occurs.