Tennessee Wastewater Operator Practice Exam

What is a potential consequence of maintaining a DO level above 0.3 mg/L in an aerobic digester during denitrification?

1. Enhanced nitrification

2. Decreased alkalinity

3. Inhibition of denitrification

4. Increased volatile solids

The correct answer is: Inhibition of denitrification

Maintaining a dissolved oxygen (DO) level above 0.3 mg/L in an aerobic digester during the denitrification process can have the consequence of inhibiting denitrification. Denitrification is a process whereby nitrates are reduced to nitrogen gas (N2) by denitrifying bacteria, which thrive in an anaerobic or low-oxygen environment. When DO levels are elevated, it creates conditions that favor nitrification and the aerobic processes, which can suppress the activity of the denitrifying bacteria. In a denitrifying environment, the goal is to reduce nitrates to nitrogen gas under low-oxygen conditions. High DO levels can disrupt this balance, preventing the complete reduction of nitrates and overall inhibiting the denitrification process. Therefore, managing and maintaining appropriate DO levels is crucial for promoting effective denitrification and maintaining the efficiency of wastewater treatment processes.