Principles and Practice of Engineering (PE) Civil: Water Resources and Environmental (WRE) Practice Exam 2025 – All-in-One Resource to Master Your PE Exam!

Protozoa are considered desirable in wastewater treatment primarily because they consume remaining bacteria. These microorganisms play a vital role in the biological treatment processes, particularly in activated sludge systems, by grazing on bacterial populations. This predation helps to control the bacterial biomass and improve the overall efficiency of the treatment process.

By consuming bacterial cells, protozoa can help maintain a more balanced microbial community, preventing the overgrowth of specific bacteria that could hinder treatment efficiency. This interaction not only assists in stabilizing the biological treatment processes but also contributes to the reduction of organic material in the effluent.

In addition to their role in managing bacterial populations, protozoa also contribute to the clarification of treated wastewater by aiding in the aggregation and settling of flocs. However, their most noteworthy function is their role in controlling and optimizing the bacterial population, ensuring that the wastewater treatment processes function effectively.