Basic Wastewater Operator Practice Exam

In wastewater treatment, what is the consequence of low dissolved oxygen levels?

1. Enhanced nitrification

2. Increased anaerobic decomposition

3. Rapid pathogen reduction

4. Improved settling rate

The correct answer is: Increased anaerobic decomposition

Low dissolved oxygen levels in wastewater treatment can lead to increased anaerobic decomposition. This process occurs when there is insufficient oxygen present in the environment for aerobic bacteria to thrive. Instead of aerobic decomposition, which effectively breaks down organic materials while utilizing oxygen, anaerobic bacteria take over the decomposition process in low oxygen conditions. This results in the production of methane and other byproducts rather than carbon dioxide and water, which would typically be the outcome in an oxygen-rich environment. In addition to changing the byproducts of decomposition, the rise of anaerobic processes can negatively impact the overall treatment efficiency. It can cause the release of foul odors and lead to the generation of hydrogen sulfide and other gases that can present operational challenges at wastewater treatment facilities. Understanding the role of dissolved oxygen is crucial for operators to maintain an effective treatment process and ensure compliance with environmental regulations.