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Drinking Water

Iron bacteria

October 13, 2010
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What they are
  • Living organisms in nature, identified by various names, including: Gallionella, Sphaerotilus, Crenothrix, Sidelocapsa or Leptothrix.

  • Iron bacteria in water use dissolved ferrous iron (Fe+2) and oxygen as part of their normal metabolic processes. Grow in darkness or light.

Growth creates a jelly-like slime that can build up on well screens, inside pipes and water treatment equipment, and in toilets and other plumbing fixtures. (Slime can also be caused by other types of bacteria.)

Most serious:
  • Reduced well yields, plugging and “sliming” of water system equipment

  • Corrosion of metal water system components

  • Foul odor of water that may resemble smell of fuel oil, cucumbers or sewage

  • Discoloration of water when masses break free.

Also: Appears naturally in some surface waters as brownish or reddish slimy masses or iridescent sheen on surface.

Occurrence/Health Effects:
  • Occurs in surface water or well water containing iron — even very low levels of iron — as long as the water has some free oxygen.

  • A “nuisance” contaminant — no known health effects.

Iron bacteria is not listed by the US Environmental Protection Agency (EPA) as either a primary or secondary contaminant.

Iron itself is a secondary contaminant, meaning that it can have undesirable effects on water’s taste, odor or appearance, but its levels are not enforceable under federal law. EPA sets a recommended maximum level for iron in drinking water at 0.3 milligrams per liter (mg/L), or 0.3 parts per million (ppm).

Water treatment:
  • Prevention: Sanitizing of well-drilling equipment and/or water treatment equipment.

  • Removal of existing problem: shock chlorination

  • Maintenance:
    • Oxidation-disinfection with continuous feed and longer contact times with either chlorine, ozone, hydrogen peroxide or potassium permanganate. Follow with filtration: activate carbon or calcite filter when using chlorine, MnZ/anthracite filter when using potassium permanganate.
    • Also a help: removal of ferrous iron by ion exchange or oxidation/filtration.

Sources: US EPA, Wisconsin Department of Natural Resources, Water Quality Association, National Ground Water Association.
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