Excessive dissolved oxygen (DO) in the Anoxic Zone impacts which biological process?

In wastewater treatment, the Anoxic Zone plays a critical role in the denitrification process, which is responsible for converting nitrate (NO3-) to nitrogen gas (N2) under low-oxygen conditions. For denitrification to occur effectively, an environment with low or no dissolved oxygen is essential, as oxygen competes with nitrate for available electron donors. Excessive dissolved oxygen in the Anoxic Zone inhibits the growth of denitrifying bacteria, therefore preventing them from efficiently performing their function of reducing nitrate to nitrogen gas. This can lead to the accumulation of nitrates in the treated effluent and ultimately impact the effectiveness of the treatment process related to reducing nitrogen compounds.

The other biological processes listed do not occur in the Anoxic Zone or are not negatively impacted by high levels of dissolved oxygen to the same extent. For instance, nitrification requires aerobic conditions and is not performed in the Anoxic Zone, while carbonaceous removal typically benefits from the presence of oxygen. Consequently, understanding the precise conditions required for each biological process is crucial for optimizing wastewater treatment efficiency.