Tennessee Wastewater Operator Practice Exam

What would be the consequence of excessive loading in a secondary treatment process?

1. Reduced aeration efficiency

2. Improved clarification

3. Increased nutrient removal

4. Lower energy consumption

The correct answer is: Reduced aeration efficiency

Excessive loading in a secondary treatment process can lead to reduced aeration efficiency. In secondary treatment, microorganisms are utilized to break down organic matter in wastewater. When the organic load—essentially the amount of biodegradable material—exceeds the system's capacity, the microorganisms can become overwhelmed. This overload means that not all of the organic material can be processed effectively, thereby reducing the overall efficiency of aeration. As the process becomes less efficient, the dissolved oxygen levels may drop because the microorganisms require oxygen for their metabolic activities. Furthermore, a high load can lead to increased competition among microorganisms for limited resources, resulting in an overall decrease in their effectiveness. In severe cases, it may also cause system failures, such as sludge bulking or washout of microorganisms. In contrast, improved clarification, increased nutrient removal, and lower energy consumption would not typically occur with excessive loading. These outcomes generally require optimal loading conditions where the treatment system can efficiently process the wastewater without being stressed.