Tennessee Wastewater Operator Practice Exam

What is the typical velocity of square and rectangular grit basins?

1. 0.1 m/s (0.3 ft/sec)

2. 0.3 m/s (1 ft/sec)

3. 0.6 m/s (2 ft/sec)

4. 1.0 m/s (3.3 ft/sec)

The correct answer is: 0.3 m/s (1 ft/sec)

In wastewater treatment, grit basins are designed to remove inorganic solids such as sand, gravel, and other particles that can cause wear and tear on process equipment. The typical velocity in square and rectangular grit basins is approximately 0.3 m/s (or 1 ft/sec). This velocity is effective for allowing heavier particles to settle while keeping lighter organic matter in suspension, promoting efficient separation of grit. The specified velocity strikes a balance between having sufficient flow velocity to carry lighter organic materials through while allowing the larger grit particles enough time to settle to the bottom. If the velocity were too low, not all grit would be effectively removed, and if it were too high, both grit and lighter materials could be swept out of the basin. Therefore, 0.3 m/s is a practical standard to ensure optimal performance in grit removal processes.