Basic Wastewater Operator Practice Exam

What is the most likely cause of pop-ups in one clarifier when the other is operating fine?

1. Filamentous bacteria

2. Old sludge

3. Young sludge

4. Broken clarifier drive

The correct answer is: Broken clarifier drive

In this scenario, the presence of pop-ups in one clarifier while the other operates normally suggests a mechanical issue rather than an issue related to the biological or sedimentation aspects of the process. A broken clarifier drive would directly affect the operation of that specific clarifier, leading to an inability to properly settle solids, which can cause materials to rise or "pop-up" instead of settling to the bottom. When a clarifier's drive mechanism is compromised, it can fail to maintain the proper flow rates and hydraulic conditions required for effective sedimentation. This results in poor performance, characterized by the issues like pop-ups. In contrast, filamentous bacteria, old sludge, and young sludge typically relate to the biological treatment aspects and characteristics of the sludge, which would tend to cause problems in both clarifiers rather than specifically one. These conditions might influence overall treatment performance but would not typically cause a single clarifier to malfunction in the manner described. Thus, the mechanical failure of the drive mechanism is the most plausible explanation for the observed symptoms.