Water, Air, and Soil Pollution

, Volume 99, Issue 1–4, pp 43–54 | Cite as

The Freshwater Floc: A Functional Relationship of Water and Organic and Inorganic Floc Constituents Affecting Suspended Sediment Properties

  • I.G. Droppo
  • G.G. Leppard
  • D.T. Flannigan
  • S.N. Liss


Flocculated fine-grained sediment is a complex matrix of microbial communities and organic (detritus, cellular debris and extracellular polymers) and inorganic material. Suspended flocs within any aquatic system play a significant ecological role as they can regulate the overall water quality through their physical, chemical and/or biological activity. This paper investigates the complex structural matrix of riverine flocs over a large range of magnifications using correlative microscopic techniques. The significance of floc structural characteristics [(size, shape, porosity, density, inorganic composition, organic composition (bacteria and fibrils)] on the physical (eg. transport and settling), chemical (eg. adsorbing/transforming contaminants and nutrients), and biological (eg. biotransformation and habitat development) behaviour of a floc is investigated. Results suggest that it is the floc's internal structure that has a significant impact on controlling the above floc behaviours. This internal structure is complex and is often dominated by the existence of a three-dimensional matrix of fibrillar material secreted by the active microbial community within the floc. This matrix, in conjunction with the inorganic and bioorganic (active and inactive) constituents of a floc, provides an intricate pore structure that may result in water being an important bound component of a floc. These complex interactive structural and functional properties of a floc are considered to influence a floc's behaviour both physically in how it is transported or settled, chemically in how it adsorbs/transforms contaminants and nutrients, and biologically in how it develops a diverse microhabitat capable of modifying the structural, chemical and biological makeup of the floc.

freshwater floc flocculation bacteria fibrils pores inorganic particles settling size and structure 


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Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • I.G. Droppo
    • 1
    • 2
  • G.G. Leppard
    • 1
    • 3
  • D.T. Flannigan
    • 3
  • S.N. Liss
    • 4
  1. 1.National Water Research InstituteBurlingtonCanada
  2. 2.Department of GeographyUniversity of ExeterExeterUK
  3. 3.Department of BiologyMcMaster UniversityHamiltonCanada
  4. 4.Department of Applied Chemical and Biological SciencesRyerson Polytechnic UniversityTorontoCanada

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