Tennessee Wastewater Operator Practice Exam

What occurs to ammonia generated through the breakdown of volatile solids?

1. It is released as a harmful gas

2. It combines with carbon dioxide to raise alkalinity

3. It is entirely absorbed by the digester

4. It decreases the digestion efficiency

The correct answer is: It combines with carbon dioxide to raise alkalinity

The correct answer highlights the process in which ammonia, a byproduct of the breakdown of volatile solids during anaerobic digestion, combines with carbon dioxide to form ammonium bicarbonate. This reaction is significant because it helps to raise the alkalinity of the digester environment. High alkalinity is essential for maintaining a stable pH level during digestion, which is necessary for the activity of methanogenic bacteria that drive the anaerobic digestion process. Inadequate alkalinity can lead to a drop in pH, which might hinder the digestion process and affect the overall performance of the digester. This increase in alkalinity through the formation of ammonium bicarbonate can also play a role in buffering, ensuring that the pH remains within the optimal range for microbial activity. Thus, the interaction between ammonia and carbon dioxide contributes positively to the digestion efficiency, facilitating a sustainable and effective treatment process. The other options present varying ideas about ammonia's fate, but they do not align with the biochemical processes occurring in anaerobic digesters. For instance, while ammonia can be a harmful gas under certain conditions, in the context of digestion, its reaction with carbon dioxide to form ammonium bicarbonate is a beneficial biochemical pathway.