Tennessee Wastewater Operator Practice Exam

In terms of activated sludge systems, what does "bulking" refer to?

1. High settling rate

2. Poor sludge quality

3. Excessive foam production

4. Poor floc formation

The correct answer is: Poor floc formation

Bulking in activated sludge systems specifically refers to poor floc formation, which is when the sludge does not form properly into compact, dense aggregates. Instead, the sludge remains in a dispersed state, causing issues during the settling process in secondary clarifiers. This poor floc formation can lead to an increased volume of sludge that rises to the surface or remains suspended in the water column, making it difficult to achieve adequate separation of treated water from the sludge. This scenario ultimately reduces the efficiency of the wastewater treatment process and can lead to problems such as decreased removal of contaminants and treatment performance. Understanding bulking is critical for wastewater operators because it can influence the overall operation of the plant and requires corrective actions to improve the floc structure, such as adjusting aeration conditions, managing the return activated sludge (RAS) flow, or optimizing the organic loading.