Basic Wastewater Operator Practice Exam

What is a common indicator of poor settling in a clarifier?

1. Low flow rates

2. High turbidity

3. Varying BOD levels

4. Stable pH levels

The correct answer is: High turbidity

High turbidity is a common indicator of poor settling in a clarifier because it reflects the concentration of suspended solids that have not successfully settled out of the wastewater. When solids remain in suspension, the water tends to appear cloudy, indicating that the clarifier is not efficiently removing those particles. Poor settling can be a result of various factors such as inadequate flocculation, chemical imbalances, or insufficient detention time. In contrast, low flow rates would typically support better settling because slower water movement allows particles more time to settle. Varying BOD levels do not directly indicate settling efficiency, as BOD is a measure of organic matter and not directly related to the physical process of settling. Stable pH levels also do not indicate settling problems; instead, they suggest that the chemical conditions in the treatment process are stable, which is generally a positive factor for clarifier performance.