Wastewater Treatment Operator Certification Practice Test

What is the carbon dioxide content of a properly functioning anaerobic digester?

1. 65 to 70% by volume

2. 1 to 2% by volume

3. 30 to 35% by volume

4. 40 to 60% by volume

The correct answer is: 30 to 35% by volume

In a properly functioning anaerobic digester, the carbon dioxide content typically falls within the range of 30 to 35% by volume. Anaerobic digestion is a biological process that occurs in the absence of oxygen, where organic materials are decomposed by microorganisms, resulting in the production of biogas. This biogas primarily consists of methane and carbon dioxide. The generation of carbon dioxide is a natural outcome of the metabolic processes carried out by the anaerobic bacteria. While methane usually comprises a significant portion of the biogas produced, the presence of carbon dioxide is also crucial as it is a by-product of the breakdown of organic matter. The percentage of carbon dioxide can vary depending on factors like the specific feedstock composition, the retention time in the digester, and the operational conditions maintained. Overall, maintaining the carbon dioxide levels within this range indicates that the anaerobic digestion process is functioning optimally, which is essential for effective treatment and biogas production.