Study on protozoan community structures during activated sludge bulking

Key words: 
• activated sludge bulking /
• filamentous bulking /
• non-filamentous bulking /
• protozoa

Abstract: Protozoan community structures and their population dynamics during activated sludge bulking in terms of filamentous bulking and nonfilamentous bulking were evaluated. With the excessive growth of filamentous bacteria, a sharp decrease of protozoan abundance occurred, while crawling ciliates and testae amoebae, representatively Chilodonella sp., Trochilia minuta and Centropyxis sp. appeared as the dominant populations. On the other hand, protozoan community structure during nonfilamentous bulking was less affected by the overgrowth of zoogloea. The total population, particularly, bacterivorous ciliates, showed an increasing trend. Vorticella sp. was the dominant species.