Crawling Ciliates

Treatment

Crawling Ciliates help to condense the floc by eating loosely attached bacteria around the floc edges. They are indicators of a healthy activated sludge; no treatment is necessary.

Under the Microscope and in Your Plant

Crawling ciliates are a type of protozoan that are beneficial to wastewater systems. They have groups of fused cilia on their ventral surface which are used for movements such as crawling over and through floc. These cilia are thick and robust, unlike swimming ciliates. Crawling ciliates can be identified under 100x magnification and range from 20-100 µm long. They are indicative of a healthy sludge age. Crawling ciliates are dominant after most of the soluble nutrients have been removed and dispersed bacteria are nearly absent in the bulk liquid. Crawling ciliates graze on loosely attached bacteria at the edges of floc, which helps maintain a healthy floc structure, creating more condensed floc. Unlike swimming ciliates, crawling ciliates do not feed on free bacteria.

Interesting Facts

• They often fall prey to carnivorous swimming ciliates
• One type of crawling ciliate can alter its cytoskeleton making it too large for predators to consume
• Crawling ciliates have been referred to as “the cows of wastewater” because they graze on loosely attached bacteria on the edges of floc, which helps maintain a healthy floc structure