Tennessee Wastewater Operator Practice Exam

If a sample of grit from the basin is grayish and smells like rotten eggs, what should the operator consider doing?

1. Decrease flow velocity

2. Increase flow velocity

3. Clean the basin

4. Change the pH

The correct answer is: Increase flow velocity

When a sample of grit from the basin is grayish and emits a smell reminiscent of rotten eggs, it usually indicates the presence of hydrogen sulfide, which is produced by anaerobic digestion of organic matter in the absence of sufficient oxygen. In this situation, increasing the flow velocity is a suitable response. By increasing the flow velocity, the operator can enhance the oxygenation of the basin, which can help to mitigate the anaerobic conditions that foster the production of foul-smelling gases. This action can also assist in the agitation of the grit, preventing the settling of materials and promoting better mixing, which can lead to improved overall treatment efficiency. While the other options may address different issues related to wastewater treatment, they do not directly counteract the symptoms of anaerobic conditions indicated by the grayish grit and rotten egg smell. Decreasing flow velocity could exacerbate the problem by allowing more stagnant conditions to develop. Cleaning the basin may be necessary at some point, but it does not directly influence the immediate chemical processes causing the odor. Changing the pH could alter certain characteristics of the treatment, but it would not necessarily address the anaerobic conditions causing the hydrogen sulfide production. Thus, increasing the flow velocity is a focused and effective response to the issue at