Wastewater New York State Practice Exam

Which protozoa is abundant in a good activated sludge composition?

1. Rotifers and stalked ciliates

2. Flagellates and amoebae

3. Nematodes and rotifers

4. Ciliates and diatoms

The correct answer is: Rotifers and stalked ciliates

In a good activated sludge composition, the presence of rotifers and stalked ciliates indicates a well-functioning microbial ecosystem that is capable of effectively treating wastewater. Rotifers are small, aquatic microorganisms that play a significant role in consuming bacteria and organic matter, which helps maintain the balance of the microbial community. Stalked ciliates, on the other hand, are indicative of the presence of settled biomass and contribute to the breakdown of organic materials in the sludge. Their abundance suggests that the system is stable and that the microbial community is proficient at nutrient removal and degradation processes. The other groups mentioned do not equally represent the indicators of a balanced activated sludge system. Flagellates and amoebae, while present in activated sludge, are often associated with less stable conditions, as their prevalence can indicate potential shock loading or organic imbalances. Nematodes and rotifers, although they are beneficial in some contexts, are not as definitive of a high-quality activated sludge environment as the combination of rotifers and stalked ciliates. Diatoms, typically found in more specialized or different aquatic environments, do not commonly represent typical activated sludge conditions either. Thus, the presence of rotifers and stalked ciliates is a strong marker of healthy, effective wastewater treatment