Which wastewater treatment process uses microorganisms in an anoxic environment to remove nitrogen?

Denitrification is the correct process that utilizes microorganisms in an anoxic environment to remove nitrogen from wastewater. In this process, bacteria convert nitrates (NO3-) and nitrites (NO2-) into nitrogen gas (N2), which is then released into the atmosphere. The anoxic environment, characterized by the absence of oxygen, is crucial for denitrifying bacteria to thrive, as they rely on nitrate as an electron acceptor instead of oxygen.

In contrast, nitrification involves the oxidation of ammonia to nitrite and then to nitrate in an aerobic environment, which is not suitable for denitrification. Aerobic digestion primarily focuses on the breakdown of organic matter in the presence of oxygen and does not specifically target nitrogen removal through denitrification. Phosphorus removal typically involves different biological or chemical processes and does not target nitrogen in the same way as denitrification. Therefore, denitrification is distinct in its process and purpose, making it the correct choice for the removal of nitrogen in wastewater treatment.