Basic Wastewater Operator Practice Exam

Which biological indicator is often used to assess the health of activated sludge?

1. Ciliates

2. Bacteria

3. Algae

4. Protozoa

The correct answer is: Ciliates

Ciliates serve as a crucial biological indicator for assessing the health of activated sludge in wastewater treatment processes. These microorganisms are a type of protozoa and play a significant role in the wastewater ecosystem. Their presence and abundance can indicate conditions within the activated sludge system, as they are sensitive to environmental changes. A healthy activated sludge environment will typically harbor a diverse population of ciliates, which are effective in consuming bacteria and organic matter, thus contributing to the overall treatment efficiency. The presence of specific types of ciliates can reflect the system's stability and the effectiveness of the biological treatment process. In contrast, while bacteria are essential for breaking down organic pollutants, they are less indicative of the system's overall health compared to ciliates. Algae are more related to nutrient levels and primary production rather than the specific health of activated sludge. Protozoa, although they can indicate biological activity, are a broader category that includes ciliates, making ciliates a more precise indicator within that group.