Tennessee Wastewater Operator Practice Exam

What physical condition can affect the dissolved oxygen levels in water?

1. Temperature

2. pH level

3. Salinity

4. All of the above

The correct answer is: All of the above

Dissolved oxygen (DO) levels in water are influenced by a variety of physical and chemical factors, making the choice of "all of the above" correct. Temperature plays a significant role in determining how much oxygen water can hold; colder water can hold more dissolved oxygen than warmer water. As temperature increases, the solubility of oxygen decreases, which means that warmer water is often associated with lower dissolved oxygen levels. pH levels also affect dissolved oxygen. The chemical and biological processes that occur in water can be influenced by acidity or alkalinity, which in turn can impact the growth of organisms that produce oxygen through photosynthesis and consume it through respiration. Salinity, which refers to the salt concentration in water, can also impact dissolved oxygen levels. Increased salinity can lower the solubility of oxygen, leading to reduced levels of dissolved oxygen available for aquatic life. Considering these points, the correct choice encompasses all provided options as they each uniquely contribute to affecting oxygen levels in aquatic ecosystems.