Texas Wastewater Class B Practice Exam

Which nitrogen transformation process involves the conversion of ammonium to nitrates?

1. Ammonification

2. Nitrification

3. Denitrification

4. Fixation

The correct answer is: Nitrification

The process that involves the conversion of ammonium to nitrates is known as nitrification. This is a two-step aerobic process carried out by specialized bacteria. First, ammonium (NH4+) is oxidized to nitrite (NO2-) by bacteria such as Nitrosomonas species. The nitrite is then further oxidized to nitrate (NO3-) by other bacteria, primarily Nitrobacter species. Nitrification is crucial in the nitrogen cycle as it helps to assimilate ammonia, which can be toxic at high concentrations, into nitrates, which are more easily taken up by plants and are less harmful in the environment. Ammonification, on the other hand, is the process where organic nitrogen from decomposing organic matter is converted into ammonia. Denitrification involves the reduction of nitrates back to nitrogen gas (N2), completing the nitrogen cycle by returning nitrogen to the atmosphere. Fixation refers to the process of converting atmospheric nitrogen gas (N2) into ammonia, making it available for biological processes. Each of these processes plays a unique role in nitrogen transformation, but nitrification specifically focuses on the conversion of ammonium to nitrate.