Tennessee Wastewater Operator Practice Exam

What effect does nitrification have on alkalinity levels?

1. It increases alkalinity

2. It has no effect on alkalinity

3. It can cause pH to decrease

4. It stabilizes the pH levels

The correct answer is: It can cause pH to decrease

Nitrification refers to the microbial process where ammonia (NH3) is converted into nitrite (NO2-) and then into nitrate (NO3-). This biological oxidation is a critical step in wastewater treatment as it helps in the removal of toxic ammonia from the wastewater before it is discharged into the environment. During nitrification, the conversion of ammonia into nitrate involves the consumption of hydroxide ions (OH-) from the water. As hydroxide ions are removed, the concentration of hydrogen ions (H+) may increase, leading to a decrease in pH levels. This process can lower the alkalinity of the water because alkalinity, which is a measure of the water’s capacity to neutralize acids, is closely associated with the presence of bicarbonate (HCO3-) and carbonate (CO32-) ions. When alkalinity decreases, pH levels can drop, often resulting in more acidic conditions. Thus, the correct answer is that nitrification can cause pH to decrease, as it utilizes components related to alkalinity in its biochemical reactions. Understanding this relationship is crucial for wastewater operators to maintain optimal conditions in treatment processes, ensuring that pH levels do not fall below acceptable ranges that could harm both microbial activity and effluent quality.