Tennessee Wastewater Operator Practice Exam

What method can be employed to control velocity in a grit channel to achieve designated velocity ranges?

1. Increase flow rate

2. Line the sides with bricks or blocks

3. Install additional grit pumps

4. Reduce channel length

The correct answer is: Line the sides with bricks or blocks

Controlling the velocity in a grit channel is essential in wastewater treatment, as it allows for the effective separation of grit from the wastewater. The correct method is to line the sides of the channel with bricks or blocks. This technique can create a rougher surface, which can increase friction and help to dissipate energy in the flowing water. As a result, the velocity of the water can be effectively controlled to stay within the designated ranges that facilitate optimal grit settling. In contrast, increasing the flow rate would typically raise the velocity of the water, potentially leading to grit being carried along rather than settling out. Installing additional grit pumps would also increase flow or turbulence, which can disrupt the required settling conditions. Reducing channel length may not effectively control the velocity itself, as it primarily alters the distance the water travels without directly modifying the flow characteristics or interaction with the channel structure. Thus, lining the sides with a rough material, such as bricks or blocks, serves as a means to maintain the required velocities in a more controlled and efficient manner.