Tennessee Wastewater Operator Practice Exam

What process involves injecting low pressure air below the water surface to transfer DO into the liquid?

1. Surface aeration

2. Diffused aeration

3. Forced aeration

4. Static aeration

The correct answer is: Diffused aeration

The process that involves injecting low-pressure air below the water surface to transfer dissolved oxygen (DO) into the liquid is known as diffused aeration. This method utilizes aeration systems that often consist of a network of diffusers, which release air into the water in fine bubbles. The small size of these bubbles increases the surface area for gas exchange, allowing for more effective dissolution of oxygen into the water. Diffused aeration is essential in wastewater treatment because it enhances the growth of aerobic bacteria, which require oxygen for the biodegradation of organic matter. The oxygen transferred into the liquid aids in maintaining proper biological activity in treatment systems. In contrast, surface aeration involves exposing the water surface to air, which relies on atmospheric pressure to encourage oxygen transfer, but often does so less efficiently than diffused aeration. Forced aeration typically involves the use of fans or blowers to push air into a system, but not specifically underwater. Static aeration does not involve mechanical pumping of air; instead, it relies on passive methods, making it less effective than diffused aeration for achieving the required oxygen levels in wastewater treatment processes.