Dive into the 2026 NY Wastewater Exam – Flush Away the Competition with Confidence!

The presence of numerous rotifers in an activated sludge system typically indicates a well-established ecosystem within the system, which often correlates with an old activated sludge and high Mean Cell Residence Time (MCRT). Rotifers are a type of microfauna that feed on bacteria and can thrive in environments where bacteria populations are robust and balanced.

A higher MCRT suggests that there is a longer retention time for the microorganisms, allowing for more stable microbial communities, including the growth of rotifers. When MCRT is high, it often means that the system is mature and has developed a diverse microbial population, indicating healthy biological activity and the breakdown of organic matter within the wastewater.

In contrast, a new treatment process typically wouldn’t support a large population of rotifers, as those systems are still establishing their microbial communities. A lack of bacteria would lead to a less functional system and would not support rotifer populations since their food source (the bacteria) would be diminished. Therefore, the presence of numerous rotifers is best interpreted as a sign of an old activated sludge system with high MCRT, indicating effective treatment performance and stability in the biological process.