Protozoan Communities and Their Contribution to Predation on in Aerobic Granular Sludge
Feng, Zhaolu Yang, Yi de Ruijter, Norbert CA Sutton, Nora B van Loosdrecht, Mark CM Schmitt, Heike
Feng, Zhaolu
Yang, Yi
de Ruijter, Norbert CA
Sutton, Nora B
van Loosdrecht, Mark CM
Schmitt, Heike
Series / Report no.
Open Access
Type
Journal Article
Article
Article
Language
en
Date of publication
2025-10-27
Year of publication
Research Projects
Organizational Units
Journal Issue
Title
Protozoan Communities and Their Contribution to Predation on in Aerobic Granular Sludge
Translated Title
Published in
Environ Sci Technol 2025; 59(44):23916-23925
Abstract
Protozoa contribute to water purification through predation in wastewater treatment systems. Full-scale aerobic granular sludge (AGS) reactors treating municipal wastewater contain AGS of varying sizes, with those larger than 2 mm dominating. These size fractions exhibit different sludge morphologies and microbial communities. To date, little is known about protozoan communities and their role in the removal of human-associated bacteria (like pathogens) in AGS plants, particularly across different size fractions. This study conducted uptake experiments with fluorescent , as a model for human-associated bacteria, followed by microscopic observation to investigate protozoan communities and their predatory behavior in six AGS size fractions and activated sludge collected from full-scale municipal wastewater treatment plants. Sessile ciliates, particularly and , dominated protozoan populations across six AGS size fractions, with being more abundant in larger AGS fractions (>1 mm) and in smaller fractions (<1 mm). Additionally, microcosm experiments under aerobic (including predation) and anoxic conditions (excluding predation) revealed that predation was likely to be the main removal pathway, contributing an additional 0.5 to 2.5 log CFU mL reduction over a combination of non-predatory biological and abiotic processes. Larger AGS fractions showed greater predation capacity, linked to higher abundance, while activated sludge, dominated by , resembled smaller AGS fractions with lower predation capacity. These findings advance the understanding of the distribution of protozoan communities and their contribution to removal by predation in AGS wastewater treatment.