Which statement best describes denitrification in wastewater treatment?

Which statement best describes denitrification in wastewater treatment?

• A. Nitrification requires low oxygen.
• B. Denitrification requires high oxygen.
• C. Denitrification requires low/zero oxygen and a carbon source.
• D. Nitrification converts nitrate to nitrite.

Answer: (C)

Denitrification is the microbial reduction of nitrate to nitrogen gas, and it only happens in an environment with little or no oxygen. In wastewater treatment, this process removes nitrogen by using nitrate as the electron acceptor instead of oxygen. A carbon source must be available because the bacteria use organic carbon as the electron donor to drive the reduction of nitrate. So, denitrification requires both low/zero oxygen (anoxic conditions) and a carbon source to proceed effectively. This is why the statement describing denitrification as needing low/zero oxygen and a carbon source is the best fit. In contrast, nitrification is an aerobic process that requires oxygen to convert ammonia first to nitrite and then to nitrate, so it does not describe denitrification. Also, denitrification does not occur with high oxygen, and nitrification does not convert nitrate to nitrite (that step is part of nitrification’s overall process, not denitrification).

Denitrification is the microbial reduction of nitrate to nitrogen gas, and it only happens in an environment with little or no oxygen. In wastewater treatment, this process removes nitrogen by using nitrate as the electron acceptor instead of oxygen. A carbon source must be available because the bacteria use organic carbon as the electron donor to drive the reduction of nitrate. So, denitrification requires both low/zero oxygen (anoxic conditions) and a carbon source to proceed effectively.

This is why the statement describing denitrification as needing low/zero oxygen and a carbon source is the best fit. In contrast, nitrification is an aerobic process that requires oxygen to convert ammonia first to nitrite and then to nitrate, so it does not describe denitrification. Also, denitrification does not occur with high oxygen, and nitrification does not convert nitrate to nitrite (that step is part of nitrification’s overall process, not denitrification).