Tennessee Wastewater Operator Practice Exam

What characteristic defines positive displacement blowers?

1. Varying airflow rates

2. Altitude sensitivity

3. Constant airflow rates over varying pressures

4. Low energy consumption

The correct answer is: Constant airflow rates over varying pressures

Positive displacement blowers are defined by their ability to deliver a constant airflow rate regardless of changes in pressure. This distinctive feature is a result of the operation principle of positive displacement devices, which work by trapping a fixed volume of air and then forcing it into the discharge line. Since the displacement of air is consistent with the mechanical design, the output flow remains steady even if the system pressure fluctuates. This characteristic is particularly beneficial in applications where a stable air supply is crucial for process stability, ensuring that systems relying on air delivery can operate effectively without concern for varying pressure conditions. In contrast, other types of blowers, such as centrifugal blowers, may experience variations in flow rate with changing pressures, leading to less predictable performance. Understanding this constant airflow output is essential for wastewater operators when selecting equipment for aeration processes, as maintaining the appropriate oxygen levels is critical for the biological treatment of wastewater.