Texas Wastewater Class B Practice Exam

If a municipal wastewater effluent has a high nitrate level and low ammonia level, what does this indicate?

1. The effluent is contaminated

2. It has received a low degree of aerobic treatment

3. It has received a high degree of aerobic treatment

4. It is ready for discharge

The correct answer is: It has received a high degree of aerobic treatment

The correct answer indicates that the effluent has undergone a high degree of aerobic treatment. In wastewater treatment, nitrification is an aerobic process where ammonia is converted into nitrate by specific bacteria. If a municipal wastewater effluent shows high nitrate levels accompanied by low ammonia levels, it suggests that the ammonia has been effectively oxidized to nitrate through aerobic processes. This transformation indicates that the treatment system is functioning well, facilitating sufficient oxygen for the aerobic bacteria to thrive and complete the nitrification process. The presence of high nitrate levels is a common outcome of efficient aerobic treatment, while low ammonia levels confirm that the ammonia has been almost entirely processed. In contrast, high ammonia levels or low nitrate levels would suggest either poor treatment or that the wastewater has not been adequately aerated. Therefore, the observation of high nitrates and low ammonia is a sign of efficient aerobic decomposition of nitrogen compounds.