Tennessee Wastewater Operator Practice Exam

What happens when ammonia combines with dissolved carbon dioxide during endogenous respiration?

1. Alkalinity decreases

2. Alkalinity stays the same

3. Alkalinity increases

4. Alkalinity fluctuates

The correct answer is: Alkalinity increases

During endogenous respiration, microorganisms utilize stored nutrients for energy, leading to the production of ammonia. When ammonia combines with dissolved carbon dioxide in the presence of water, it can form ammonium ions (NH4+) and bicarbonate ions (HCO3-). This process contributes to an increase in alkalinity because the production of bicarbonate ions raises the buffering capacity of the water. The formation of bicarbonate plays a crucial role in maintaining the pH of the wastewater. As more bicarbonate is produced, it helps to neutralize acids that may be present during other biochemical processes, effectively raising the overall alkalinity of the system. This interaction is significant in biological treatment processes, where maintaining a stable pH and sufficient alkalinity is necessary for the optimal performance of the microorganisms involved. Considering the dynamics of pH and alkalinity, it's evident that the reaction enhances the buffering capacity rather than diminishing it, leading to the conclusion that alkalinity increases as a result of this biochemical interaction.