Tennessee Wastewater Operator Practice Exam

What term describes the loss of mixed liquor suspended solids (MLSS) of 30% or more from the aeration basin due to improper operation?

1. Overflow

2. Washout

3. Runoff

4. Drainage

The correct answer is: Washout

The term that describes the loss of mixed liquor suspended solids (MLSS) of 30% or more from the aeration basin due to improper operation is "washout." This phenomenon occurs when the flow rate through the aeration basin is too high, resulting in the removal of suspended solids from the system. When washout happens, the concentration of solids is significantly reduced, which can inhibit the biological treatment process, as the microorganisms responsible for breaking down organic matter also get washed out. In the context of wastewater treatment, maintaining appropriate levels of MLSS is crucial for effective treatment. An excessive washout can be caused by various factors, such as sudden changes in inflow, equipment malfunction, or operational mistakes that lead to unstable conditions in the aeration basin. Recognizing and addressing washout is essential for operators to ensure efficient treatment processes and compliance with regulatory requirements. Other terms such as overflow, runoff, and drainage refer to different processes that do not specifically describe the significant loss of MLSS from aeration due to operational issues.