Tennessee Wastewater Operator Practice Exam

What are the two types of positive displacement blowers mentioned?

1. Rotary lobe and rotary screw

2. Centrifugal and axial

3. Diaphragm and centrifugal

4. Scroll and rotary vane

The correct answer is: Rotary lobe and rotary screw

The correct answer is that the two types of positive displacement blowers are rotary lobe and rotary screw. Positive displacement blowers operate by trapping a fixed volume of air and then forcing it into a discharge pipe. Rotary lobe blowers function by using two rotors that turn in opposite directions, creating a vacuum that draws air in and then compressing it as it moves through the blower. This design provides a steady flow of air and operates well at lower pressures, making it suitable for many wastewater applications. Rotary screw blowers, on the other hand, use two rotors that work in harmony to compress the air as it is drawn in. The design allows for efficient air movement, producing a continuous flow that can handle higher pressures compared to rotary lobe blowers. They are known for their energy efficiency and lower noise levels. These two types of blowers are commonly used in wastewater treatment facilities for aeration processes, making the distinction between them essential for operators to understand in order to select the right equipment for specific needs.