What does nitrogenous oxygen demand (NOD) measure in wastewater treatment?

Nitrogenous oxygen demand (NOD) specifically measures the amount of oxygen consumed by nitrifying bacteria during the oxidation of ammonia to nitrate in wastewater. This process is part of the nitrogen removal in wastewater treatment, as these bacteria convert ammonia, a form of nitrogen that can be harmful in high concentrations, into nitrate, which is less toxic.

In this context, the calculation of NOD is crucial for understanding how much oxygen is required to effectively treat wastewater with significant ammonia concentrations. By focusing on the activity of nitrifying bacteria, NOD provides insights into the biological treatment processes in place and helps operators manage aeration and oxygen supply efficiently to ensure optimal treatment performance.

The other options relate to different aspects of wastewater treatment; for instance, the total biochemical oxygen demand encompasses all organic matter, while the presence of ammonia or the amount of organic carbon focuses on different parameters that may not directly correlate with the nitrification process measured by NOD.