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SEM-EDS for determining the phosphorus content in activated sludge EPS
1Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, 0002, South Africa.
Summary
Polyphosphate accumulating organisms (PAO) do not account for all phosphorus removal in activated sludge. Extracellular polysaccharides (EPS) also act as a phosphorus reservoir, contributing to phosphate uptake in wastewater treatment.
Area of Science:
- Environmental Science
- Microbiology
- Analytical Chemistry
Background:
- Activated sludge systems are crucial for wastewater treatment, primarily for nutrient removal.
- Polyphosphate accumulating organisms (PAO) are known to sequester phosphorus, but their contribution doesn't fully explain observed removal rates.
Purpose of the Study:
- To develop a method for in situ characterization of PAO and associated extracellular polysaccharides (EPS).
- To investigate the role of EPS in phosphorus removal within activated sludge systems.
Main Methods:
- Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS) for X-ray microanalysis.
- In situ characterization of PAO cell clusters and EPS.
- Extraction and quantification of EPS from different activated sludge samples.
Main Results:
- PAO cell clusters with associated EPS showed high phosphorus content (57-59%).
- EPS alone demonstrated significant phosphorus content (23-30%).
- Varied EPS amounts were extracted from different treatment plants, correlating with phosphate uptake.
Conclusions:
- Extracellular polysaccharides (EPS) play a significant role in phosphorus removal in activated sludge, acting as a phosphorus reservoir.
- The findings suggest a dual mechanism for phosphorus removal involving both PAO and EPS.
- Variations in EPS quantity and composition may influence the phosphate uptake efficiency of different activated sludge consortia.