Spatial arrangement of the components of activated sludge flocs

F. Zartarian, C. Mustin, J. Y. Bottero, G. Villemin, F. Thomas, L. Ailleres, M. Champenois, P. Grulois, J. Manem

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The purpose of this work was to observe the internal structure of activated sludge flocs and the relationship between the different components. Activated sludge flocs from the municipal sewage treatment plant at Nancy (France) were physically stabilized and solidified in an epoxy resin. The flocs were sliced into 0.1 μm thick sections and stained for characterisation of components and exopolymers by transmission electron microscopy. One small flee (10 μm x 20 μm), embedded in resin, was chosen and studied using a laser scanning confocal microscope. The focal plane was incremented in steps of 2 μm along the z axis of the microaggregate. In order to extract quantitative data (number of cells, flee size) a numerical treatment of the images was applied. A typical flee exhibits an unhomogeneous distribution of the mass and of the exocellular polymer matrix (mainly polysaccharides), This matrix maintains the integrity of the flee and connects most of the components. These components are isolated bacteria, waste and debris inherited from the effluent and microcolonies. The structure of the microflocs is fractal with a fractal dimension Df = 3. This large value implies that the growth of the small aggregates is possibly generated by cellular division and polymer production.

Original languageEnglish
Pages (from-to)243-250
Number of pages8
JournalWater Science and Technology
Issue number11
Publication statusPublished - 1 Dec 1994
Externally publishedYes


  • Activated sludge flocs
  • Confocal microscope
  • Embedment in epoxy resin
  • Fractal dimension
  • Internal structure
  • Microcolonies
  • Microtome sectioning
  • Polymers
  • Transmission electron microscope

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