Tennessee Wastewater Operator Practice Exam

What is the effect of colder water temperatures on dissolved oxygen levels in wastewater treatment ponds?

1. They decrease DO levels

2. They increase DO levels

3. They have no effect on DO levels

4. They cause fluctuations in DO levels

The correct answer is: They increase DO levels

Colder water temperatures generally correspond with higher dissolved oxygen (DO) levels. This phenomenon occurs because cold water can hold more oxygen than warm water. As the temperature decreases, the solubility of oxygen increases, allowing for a greater concentration of dissolved oxygen in the water. In the context of wastewater treatment ponds, this means that during colder months or in colder climates, you can expect to see higher levels of dissolved oxygen. This is beneficial for aerobic microorganisms that break down organic matter in the wastewater, as they require oxygen to thrive. Increased DO levels can enhance the efficiency of the treatment process by promoting better aerobic conditions, which are crucial for effective biological treatment. In contrast, warmer water temperatures often lead to lower dissolved oxygen levels, which can stress aquatic life and hinder the overall wastewater treatment process. Therefore, the influence of colder temperatures on dissolved oxygen is significant and is a foundational concept in understanding aquatic chemistry and wastewater treatment.