What should be the DO levels in the nitrification stage of a Rotating Biological Contactor plant?

In the nitrification stage of a Rotating Biological Contactor (RBC) plant, maintaining the correct dissolved oxygen (DO) levels is crucial for the effective conversion of ammonia to nitrate through the action of nitrifying bacteria. The appropriate range for DO during this stage is typically between 2.0 and 3.5 mg/L.

This specific range allows for optimal aerobic conditions, which are essential for the nitrification process. Nitrifying bacteria, such as Nitrosomonas and Nitrobacter, require sufficient oxygen to thrive and carry out the oxidation of ammonia (NH3) to nitrite (NO2-) and then to nitrate (NO3-). If the DO levels fall below this range, it can inhibit the metabolic processes of these bacteria, leading to reduced nitrification efficiency. Conversely, excessively high DO levels are unnecessary and can lead to excessive aeration, which does not benefit nitrification while potentially causing other operational issues.

Therefore, maintaining DO levels within the 2.0 to 3.5 mg/L range is essential to promote effective nitrification in RBC systems, ensuring that the bacteria can perform optimally in their aerobic environment.