Tennessee Wastewater Operator Practice Exam

What is a potential effect of nitrification in an aerobic digester?

1. Increase the pH

2. No effect on pH

3. Lower the pH

4. Stabilize the pH

The correct answer is: Lower the pH

Nitrification in an aerobic digester involves the oxidation of ammonia to nitrate through the activity of nitrifying bacteria. This biochemical process consumes hydroxide ions (OH-) and produces hydrogen ions (H+), which leads to a decrease in pH. As the concentration of hydrogen ions increases, the resulting effect is a lower pH in the system. This is significant in wastewater treatment because maintaining a specific pH range is crucial for the optimal performance of biological processes. A lower pH can influence the activity of microorganisms and overall digester health. In contrast, other options do not accurately reflect the biochemical transformation occurring during nitrification. An increase in pH would imply a reduction in hydrogen ions or neutralization processes, which does not occur in nitrification. Similarly, stating that there is no effect or that the pH stabilizes would not align with the well-documented impact of this process where acidity is a direct product of activity by nitrifiers. Therefore, recognizing that nitrification lowers the pH is essential for understanding the dynamics within aerobic digesters in wastewater treatment.