Texas Wastewater Class B Practice Exam

What is the acceptable range for dissolved oxygen levels in the aeration basins?

1. 0.5 mg/L and 1.5 mg/L

2. 2 mg/L and 4.0 mg/L

3. 5 mg/L and 6.0 mg/L

4. 1.0 mg/L and 3.0 mg/L

The correct answer is: 2 mg/L and 4.0 mg/L

The acceptable range for dissolved oxygen levels in aeration basins is crucial for the effective operation of wastewater treatment processes. The range of 2 mg/L to 4.0 mg/L is ideal because it provides sufficient oxygen for aerobic microorganisms to thrive. These microorganisms play a vital role in breaking down organic matter in the wastewater. If dissolved oxygen levels fall below this range, it can lead to anaerobic conditions, which reduce the efficiency of the treatment process and can result in the release of undesirable odors and potentially harmful byproducts. Maintaining optimal dissolved oxygen levels within this range ensures that biological processes can proceed effectively, promoting the stabilization of organic materials and efficient nutrient removal. The other ranges provided do not align with operational expectations for aeration basins in wastewater treatment. If levels were as low as 0.5 mg/L to 1.5 mg/L, or if they exceeded 4.0 mg/L significantly, it could hinder the treatment process, either by not providing enough oxygen for the bacteria or possibly leading to excessive aeration, which can introduce unnecessary costs and energy expenditure. Thus, 2 mg/L to 4.0 mg/L balances the needs of the microorganisms while ensuring the treatment process remains efficient.