Why do ciliates improve the quality of treated wastewater?

Ciliates are essential to the production of high-quality, clean effluent in wastewater treatment plants. Their presence improves water quality primarily through two mechanisms:

• Grazing: Ciliates graze voraciously on dispersed bacteria that would otherwise remain suspended in the water, contributing to turbidity and high bacterial levels.1
• Flocculation: Ciliates possess the ability to flocculate, or aggregate, suspended particulate matter and bacteria. This process creates larger particles that can be easily separated from the liquid during the final settlement stage of treatment.1

In contrast, treatment systems that lack sufficient ciliated protozoan communities—relying instead on only small numbers of amoebae and flagellates—typically produce turbid effluents that contain significantly higher levels of suspended solids and bacteria. By effectively removing these dispersed contaminants, ciliates ensure the final output of the treatment process is clear and of higher quality.1