Assessment by Microscopy of the Coverage of Sludge Flocs by a Nano-scale Surface Layer

Authors

  • Dorothy Pazin,

    1. Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
    2. Department of Genetics and Genomics, Boston University School of Medicine, Boston, MA, U.S. 02118
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  • John N. A. Lott,

    1. Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
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  • M. Marcia West,

    1. Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
    2. Faculty of Health Sciences Electron Microscopy Facility, McMaster University, Hamilton, ON, Canada L8N 3Z5
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  • Gary G. Leppard

    Corresponding author
    1. Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
    2. National Water Research Institute, Environment Canada, Burlington, ON, Canada L7R 4A6
    • Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
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Abstract

Flocs are irregularly shaped suspended particles of complex structure and composition that occur naturally in aquatic systems. In water treatment facilities, the settling of flocs is extremely important. Transmission electron microscopy was used to quantify the formation of a nano-scale surface layer on flocs from two laboratory bioreactors modelling a biological wastewater treatment facility. By comparing different floc populations, we demonstrated that flocs that settled quickly out of wastewater had a significant amount of this layer, whereas those with little nano-scale surface layer had poor settling properties. This morphological feature of floc ultrastructure may permit engineering manipulations that promote floc settling.

Abstract

Les flocs sont des particules suspendues de forme irrégulière qui ont une structure et une composition complexes qui se forment naturellement dans les systèmes aquatiques. Dans les installations de traitement des eaux, la sédimentation des flocs est extrêmement importante. On a eu recours à la microscopie électronique à transmission pour quantifier la formation d'une couche de surface à l'échelle nano à partir de deux bioréacteurs de laboratoire modélisant une installation de traitement des eaux usées biologique. En comparant les différentes populations de flocs, on démontre que les flocs qui se séparent rapidement de l'eau usée ont une quantité significative de cette couche nanométrique, tandis que ceux qui en ont une faible quantité sédimentent moins facilement. Cette caractéristique morphologique de l'ultrastructure des flocs pourrait permettre des manipulations d'ingénierie qui favorisent la sédimentation des flocs.

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