Population dynamics of bacteria involved in enhanced biological phosphorus removal in Danish wastewater treatment plants

Project Description

Conducted a three-year study on the microbial communities involved in Enhanced Biological Phosphorus Removal (EBPR) across 28 Danish municipal wastewater treatment plants.
Used Fluorescence In Situ Hybridization (FISH) to quantify ten key populations of polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs).
Found that PAOs—especially Tetrasphaera (27%) and Accumulibacter (3.7%)—were consistently abundant and stable across all EBPR plants.
GAOs were only present in a few plants and at much lower levels than PAOs, indicating they are not core members of EBPR systems.
Plants with no EBPR design showed significantly lower abundance of both PAOs and GAOs.
Observed correlations between specific microbial populations and wastewater characteristics:
- Competibacter with high industrial wastewater fraction
- Accumulibacter with high carbon-to-phosphorus (C/P) ratios
- Tetrasphaera with high organic loading
Each treatment plant had a unique microbial “fingerprint”, showing that community structure is plant-specific and stable over time.

The total fraction of PAO and GAO populations made up approximately 30% of the total bacterial community in EBPR plants.
The two main PAO genera identified were Accumulibacter (average 3.7%) and Tetrasphaera (average 27%), both consistently abundant and stable across all EBPR plants.
GAOs such as Competibacter and Defluviicoccus were found only sporadically and in lower abundance, particularly in plants receiving a high fraction of industrial wastewater.
Plants lacking EBPR design had significantly lower abundances of both PAOs and GAOs.
Microbial composition varied by plant but remained stable over time, creating a plant-specific microbial “fingerprint”.
Accumulibacter was positively associated with high carbon-to-phosphorus (C/P) ratios, while Tetrasphaera correlated with high organic loading conditions.

Established a microbial baseline: Quantified the presence and relative abundance of key PAO and GAO populations in Danish full-scale EBPR systems.
Identified dominant PAO species: Tetrasphaera was revealed as the dominant PAO genus, more abundant than the traditionally studied Accumulibacter.
Clarified GAO behavior: Demonstrated that GAOs are not core members of EBPR communities and are primarily influenced by specific operational factors like industrial input.
Explained performance variability: Correlations between specific microbial populations and wastewater characteristics (e.g., C/P ratio, organic loading) help explain why EBPR performance varies among plants.
Developed plant-specific microbial profiles: Showed that each treatment plant hosts a unique, stable microbial community over time, contributing to tailored operational strategies.

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