Tennessee Wastewater Operator Practice Exam

What effect can a high volatile acid concentration have on anaerobic digesters?

1. It may enhance methane production

2. It can indicate a toxic environment for methanogens

3. It directly stabilizes pH levels

4. It plays no significant role

The correct answer is: It can indicate a toxic environment for methanogens

High volatile acid concentration in anaerobic digesters can indicate a toxic environment for methanogens, which are essential microorganisms responsible for the production of methane in the digestion process. When volatile acids accumulate, usually due to an imbalance in the digestion process or excessive organic loading, they can lead to a drop in pH. Methanogens thrive in a specific pH range, typically around neutral (pH 6.8-7.5), and a significant deviation from this range can inhibit their activity, leading to reduced methane production and potential process instability. As volatile acids increase, they can create an acidic environment that is detrimental to methanogenic activity. This can lead to a negative feedback loop where decreased methanogen populations result in lower methane production, which further allows for the accumulation of volatile acids. Identifying high volatile acid levels serves as an important diagnostic tool in managing anaerobic digesters, as it signals that corrective actions may be necessary to restore balance and optimal conditions for methanogens to function effectively.