Florida Wastewater Practice Test

What is the best description of the term "anoxic"?

1. No oxygen present

2. Nearly anaerobic with little DO

3. Nearly anaerobic with very low DO, but nitrates and/or nitrites present

4. High oxygen concentration

The correct answer is: Nearly anaerobic with very low DO, but nitrates and/or nitrites present

The term "anoxic" is best described by the presence of low levels of dissolved oxygen (DO) while still allowing for the presence of nitrates and/or nitrites. This environment is essential for certain biological processes, particularly those involved in denitrification, where microorganisms utilize nitrates as an alternative electron acceptor in the absence of sufficient oxygen. In an anoxic environment, oxygen is not completely absent, which distinguishes it from truly anaerobic conditions. Anoxic conditions can support various microbial processes that are crucial for wastewater treatment, such as the conversion of nitrates to nitrogen gas, which is valuable for reducing nitrogen levels in effluent. This process helps control nutrient pollution in receiving waters, making anoxic conditions important in environmental management and wastewater treatment design. In contrast, the other descriptions do not accurately capture the nuanced state of anoxic environments. While some options highlight the absence of oxygen or high oxygen levels, they miss the hallmark characteristic of anoxic conditions – the presence of nitrates or nitrites that can be utilized biologically.