Fouling Organism

Definition - What does Fouling Organism mean?

A fouling organism is an animal or plant species that exists in water and attaches to the surface of a material immersed in the water.

When attached to a ship's hull, these organisms accumulate and grow to form undesirable layers of material. The animals may either be in their adult stages or as free larvae which then develop into adults after attaching to the surface.

Corrosionpedia explains Fouling Organism

There are over 4000 species of fouling organisms, mainly found near sea inlets and shallow waters due to the availability of nutrients. These organisms may also be introduced to other bioregions by ship hulls when the attached species release larvae and leave them at new ports.

There are two main categories of fouling organisms:

  • Micro-fouling organisms: These are mainly microbial and bacterial in nature and quickly colonize any immersed object to form a bio-film, or slime. The bio-film is a sticky coating which accumulates on the surface, providing food and a convenient interface where large macro-fouling organisms can attach. Common slimes include:
    • Diatoms
    • Bacteria
    • Protozoa

  • Macro-fouling organisms: These are larger animals and plants, and adhere either as individuals or in large colonies. These larger species pose more numerous and severe problems as compared to the micro-fouling type. In addition to the immersed materials, these species can find their way into cooling systems when water is drawn directly from natural sources such as lakes, rivers or coastal waters. Common organisms include:

    • Animal fouling organisms:
      • Oysters
      • Clams
      • Tube worms
      • Mussels
      • Barnacles
      • Hydroids
      • Bryozoans

    • Plant fouling organisms:
      • Ectocarpus (brown algae)
      • Enteromorpha (green algae)
      • Rhodophycea (red algae)

Fouling organisms lead to bio-fouling where they start growing on immersed object surfaces immediately upon submersion or when they come into contact with the surfaces, such as in cooling towers. This leads to corrosion and deterioration of metallic parts, resulting in reduced efficiency, material failure and expensive repairs.

Typical control methods to prevent or reduce the effects of fouling organisms are:

  • Use of oxidizing and nonoxidizing antimicrobials
  • Chemical or thermal treatment of water for heat exchange systems
  • Proper waste water disposal
  • Mechanical cleaning
  • Use of antifouling paints

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