Tennessee Wastewater Operator Practice Exam

Which statement is not true regarding aerobic digestion?

1. They require continuous mixing to operate effectively

2. They are always operated with a DO greater than 1mg/L

3. They convert organic waste into stable compounds

4. They produce carbon dioxide as a byproduct

The correct answer is: They are always operated with a DO greater than 1mg/L

Aerobic digestion is a biological process that relies on the presence of oxygen to break down organic matter. In this process, microorganisms consume organic waste and convert it into stable compounds, with carbon dioxide being released as one of the byproducts of respiration. The statement that aerobic digestion is always operated with a dissolved oxygen (DO) level greater than 1 mg/L is not entirely accurate. While it is essential for aerobic processes to have sufficient oxygen, the actual required DO levels can vary based on the specific design of the digester, the type of waste being treated, and the operational conditions. Some aerobic digesters might efficiently function at lower DO levels, especially if it allows for a more controlled environment for microbial activity. Continuous mixing is important for maintaining an even distribution of microorganisms and nutrients throughout the waste, which facilitates efficient breakdown. The conversion of organic waste into stable compounds is a central goal of aerobic digestion, ensuring that what remains can be safely handled or further processed. Therefore, the assertion linked to the requirement of dissolved oxygen levels is the one that does not hold true universally in the context of aerobic digestion.