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Microbial immigration in full-scale activated sludge systems is influenced by operational and design parameters
1Department of Biological Sciences, Simon Fraser University, Canada.
Water Research
|August 13, 2026
Summary
Microbial immigration significantly shapes wastewater treatment communities. We quantified immigration rates across plants, finding they depend on operational factors like solids retention time and system design.
Area of Science:
- Environmental microbiology
- Wastewater treatment engineering
- Community ecology
Background:
- Microbial immigration from influent wastewater is a key factor in activated sludge community assembly.
- Quantifying microbial immigration rates in full-scale systems has been challenging.
Purpose of the Study:
- To apply the neutral community model (NCM) to quantify microbial immigration rates (NTm) in full-scale wastewater treatment plants.
- To investigate the influence of operational parameters and system design on immigration rates.
- To assess the functional relevance of microbial immigration in activated sludge communities.
Main Methods:
- Utilized 16S rRNA gene amplicon datasets from 74 full-scale wastewater treatment plants.
- Applied recently developed inference methods and the neutral community model (NCM).
- Quantified immigration rates (NTm) and taxon-specific immigration probabilities.
Main Results:
- Determined reliable immigration rates for 31 datasets, ranging from 1.8 × 102 to 2.5 × 104.
- Immigration rates positively correlated with solids retention time (SRT) and negatively with treatment capacity.
- Attached growth systems showed lower immigration rates than suspended-growth systems.
- Abundances of denitrifiers, polyphosphate-accumulating, and glycogen-accumulating organisms correlated with immigration probabilities.
- Nitrifier abundances were higher than predicted by NCM, with lower immigration rates.
Conclusions:
- Microbial immigration rates are influenced by operational and design parameters in activated sludge systems.
- Microbial immigration plays a significant role in shaping the functional aspects of full-scale activated sludge communities.
- The NCM provides a valuable framework for quantifying microbial immigration and understanding community assembly in engineered ecosystems.
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