Anoxic zones play a crucial role in biological nitrogen removal (BNR) systems by providing the necessary conditions for denitrification. Denitrification is the process where nitrate (NO3-) is converted to nitrogen gas (N2), removing nitrogen from the wastewater. Anoxic zones are specifically designed to be low in or completely devoid of dissolved oxygen (DO), typically maintained at less than 0.5 mg/L. This lack of oxygen is essential for denitrifying bacteria to thrive. Denitrifying bacteria are facultative anaerobes, meaning they can survive in both the presence and absence of oxygen. However, they prefer to use oxygen as an electron acceptor when it is available. In the absence of oxygen, they switch to using nitrate as an electron acceptor. The denitrification process requires an organic carbon source. The denitrifying bacteria use the organic carbon to fuel the conversion of....
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