Tennessee Wastewater Operator Practice Exam

Which factor is considered the most critical in controlling anaerobic digester operations?

1. Temperature regulation

2. Volatile acids/alkalinity relationship

3. Hydraulic retention time

4. Mixing speed

The correct answer is: Volatile acids/alkalinity relationship

The volatile acids/alkalinity relationship is considered the most critical factor in controlling anaerobic digester operations because it directly influences the overall health and efficiency of the digestion process. In an anaerobic digester, microorganisms break down organic materials in the absence of oxygen, producing biogas as a byproduct. Maintaining a balanced volatile acids to alkalinity ratio is essential for the stability of the anaerobic process. When volatile acids accumulate—indicating an increase in acid-producing bacteria—this can lead to conditions that inhibit the activity of the methane-producing bacteria, causing process instability or failure. If the alkalinity is equally high, it can help buffer the system against drastic pH changes, which is crucial for optimal microbial function. Thus, maintaining this relationship is vital for optimizing biogas production and ensuring that the digestion process runs smoothly. Other factors like temperature regulation, hydraulic retention time, and mixing speed play important roles, but they do not have the same direct impact on the metabolic processes that are sensitive to changes in volatile acids and alkalinity.