California Wastewater Treatment Operator Practice Exam

An increase in the acid/alkalinity ratio for an anaerobic digester means:

1. the digester is becoming overly acidic

2. the digester is losing efficiency

3. Alkalinity levels are too high

4. Acid concentration is increasing or alkalinity is decreasing

The correct answer is: Acid concentration is increasing or alkalinity is decreasing

The correct answer indicates that an increase in the acid/alkalinity ratio for an anaerobic digester can result from an increase in acid concentration or a decrease in alkalinity. In the context of anaerobic digestion, maintaining a balanced ratio between acids and alkalinity is crucial. An increase in this ratio suggests that the environment within the digester is shifting toward higher acidity, which can negatively impact the overall digestion process. This shift can potentially be detrimental to the microbial communities responsible for breaking down organic matter, as they thrive best at stable pH levels. If acids build up excessively or alkalinity decreases significantly, it can lead to unfavorable conditions, risking digester performance. The other options, while related to digester performance, do not accurately capture the specific implications of the acid/alkalinity ratio change. The first option about becoming overly acidic could be a consequence of the increase, but it doesn't address the broader implication of both acid increase and alkalinity decrease. The mention of losing efficiency relates to the effects that an imbalance can have but does not pinpoint the exact change occurring in the acid/alkalinity ratio. Similarly, indicating that alkalinity levels are too high does not hold, as the statement describes an increase in the acid proportion rather than