Tennessee Wastewater Operator Practice Exam

What is the primary function of flow proportional weirs in a horizontal grit basin?

1. Increase turbulence

2. Collect grit

3. Maintain a constant velocity

4. Improve aeration

The correct answer is: Maintain a constant velocity

The primary function of flow proportional weirs in a horizontal grit basin is to maintain a constant velocity of flow. This is crucial for proper grit removal because it ensures that the flow rate is suitable for sedimentation processes. When the flow is consistent, it allows the grit to settle effectively at the bottom of the basin without disturbing the settled material. Maintaining a constant velocity helps to optimize the separation of grit from the wastewater, enhancing the efficiency of the grit removal process. If the velocity fluctuated significantly, it could lead to inefficiencies, where either too much grit is carried over with the effluent or too little is removed, thus impacting the overall performance of the wastewater treatment system. In contrast, other functions, such as increasing turbulence, collecting grit, or improving aeration, do not align with the primary role of the weirs in this context. The primary design goal behind flow proportional weirs is to ensure that the hydraulic conditions are stable for effective grit removal, not to introduce turbulence or actively aerate the wastewater.