Basic Wastewater Operator Practice Exam

If ammonia loading on a plant is increasing, what should the operator expect with respect to alkalinity?

1. The alkalinity will decrease

2. The alkalinity will remain the same

3. The alkalinity will not change

4. Ammonia has nothing to do with alkalinity

The correct answer is: The alkalinity will decrease

When ammonia loading on a wastewater treatment plant increases, the operator should expect a decrease in alkalinity. This phenomenon occurs because the nitrification process, which involves the conversion of ammonia to nitrate, consumes alkalinity. During nitrification, ammonia is oxidized to nitrite and then to nitrate, and this reaction requires hydroxyl ions (OH-) from the water, resulting in a consumption of bicarbonate (HCO3-) in the process. As the bacteria convert ammonia to nitrate, they effectively neutralize the bicarbonate — which acts as a buffer for alkalinity — leading to a reduction in the overall alkalinity of the system. This is particularly important for operators to monitor because low alkalinity can hinder the nitrification process, making it crucial to manage ammonia levels accordingly to maintain an effective treatment process. Understanding this relationship helps operators anticipate changes in treatment performance and take appropriate corrective measures when necessary.