Wastewater New York State Practice Exam

What is the primary function of a vacuum relief valve on an anaerobic digester?

1. To release excess pressure

2. To maintain temperature

3. To add air to the digester

4. To enhance mixing

The correct answer is: To add air to the digester

The primary function of a vacuum relief valve on an anaerobic digester is crucial for maintaining the integrity of the system and ensuring its efficient operation. This valve is designed to prevent a vacuum from forming inside the digester, which can occur as a result of the biological processes taking place and the consumption of gases produced by the digestion of organic material. When anaerobic digestion occurs, gases such as methane and carbon dioxide are produced. If these gases are removed from the system, a vacuum can form if there is no proper means of balancing the pressure. The vacuum relief valve allows air to enter the digester when the internal pressure drops below atmospheric pressure, thus preventing structural damage due to potential implosion or deformation of the digester walls. The options refer to other important functions in a digester but do not address the vacuum relief valve's key role in pressure management. While releasing excess pressure is important, the valve specifically serves to counteract vacuum conditions rather than manage excess pressure. Maintaining temperature, enhancing mixing, and adding air are all pertinent to digestion processes, but they do not directly reflect the primary purpose of the vacuum relief valve, which is focused on preventing vacuum conditions that could compromise the system’s operation.