Texas Wastewater Class B Practice Exam

Which microorganisms are considered the most numerous and important in activated sludge?

1. Viruses

2. Protozoa

3. Bacteria

4. Fungi

The correct answer is: Bacteria

Bacteria are considered the most numerous and important microorganisms in activated sludge systems. They play a crucial role in the biological treatment of wastewater by degrading organic matter. In the activated sludge process, bacteria form flocs that help in the aggregation of solids and the removal of contaminants. Their metabolic activities lead to the breakdown of pollutants, which is essential for maintaining water quality and treating wastewater effectively. While viruses can be abundant in various environments, they do not have a direct role in the breakdown of wastewater pollutants like bacteria do. Protozoa are beneficial as they feed on bacteria and help maintain the microbial balance within the system, but they are significantly less numerous than bacteria. Fungi contribute to the decomposition of organic matter but are not as central to the activated sludge process as bacteria. Therefore, the prominence of bacteria in both number and function makes them the key microorganisms in this context.