Tennessee Wastewater Operator Practice Exam

What is the most critical factor in controlling the anaerobic digester operation?

1. Temperature

2. Volatile acids/alkalinity relationship

3. pH level

4. Mixing speed

The correct answer is: Volatile acids/alkalinity relationship

The most critical factor in controlling the anaerobic digester operation is the volatile acids/alkalinity relationship. This relationship is crucial because it reflects the balance between acid-producing and acid-consuming microorganisms in the digester. If volatile fatty acids accumulate excessively, it indicates that the acid production is outpacing the neutralization by alkalinity, which can lead to conditions that inhibit the overall digestion process. The stability of the anaerobic digestion process depends on maintaining this balance. A healthy level of alkalinity helps to buffer the digesting material against changes in pH that can result from the accumulation of volatile fatty acids. If the alkalinity is sufficient to neutralize the acids, the process continues to operate effectively, leading to optimal digestion and biogas production. However, if this relationship is disturbed, it can lead to process instability, reduced methane production, and even digester failure. This dynamic highlights why managing the volatile acids/alkalinity relationship is central to anaerobic digester operation. Maintaining it ensures that the digester can effectively break down organic materials while producing biogas in a stable and efficient manner.