Iron Bacteria

What Are Iron Bacteria?

Iron bacteria are naturally occurring organisms in the environment. They typically exist in the top soil layers in limited numbers and obtain energy by oxidising soluble ferrous iron into insoluble ferric iron which then precipitates out of water. These precipitates gives the bacteria (or the water in which they are found) the typical brown coloration. Growth of iron bacteria results into thread-like slimes which together with the ferric iron form a voluminous mass in water. Iron bacteria have a temperature growth range of between 20-37oC

Sources Of Iron Bacteria

Studies of ore deposits of about 300 million years ago have shown to contain fossils of a range of iron bacteria. Through out history, there are reports of water from wells, rivers and creeks being stained blood red or brown and becoming undrinkable presumably due to the growth of iron bacteria. They were first studied in detail in the 1800s and since then many species of iron bacteria have been identified. Some of the common ones are Gallioniella, Sphaerotilus, Leptothrix, Cronothrix, and others.

The most common origin for iron bacteria in water bodies or water is their entry during mining, boring or drilling activities and equipment installation. As they are generally found in soil, mud sediments or bogs, contamination of water or piping systems and equipment with the same can results into a flourished growth.

Iron Bacteria And Health Issues

Iron bacteria are not known to cause health problems in people, but they may have the following unpleasant and possibly expensive effects:

  • Unpleasant odours and taste in water reducing potability of water
  • Increased organic content in water favouring the multiplication of other bacteria
  • Piping clogged with rusty sludge
  • Corroded piping and plumbing equipment
  • Increased chances of sulphur bacteria infestation

Iron bacteria cause the development of an orange-brown slime on water fixtures and the clogging of devices, sometimes to an extreme. The clogs can build-up at the ends of faucets, in screens on laundry machines, on pump impellers, and on the inside of pipes and tanks. The material often builds on a surface over time, and then breaks off in a large, single mass causing a clog.

Iron bacteria can also cause taste and odour problems in the water as they live, reproduce and die. These micro-organisms make water unsightly and raise a question as to the water’s purity. The bacteria are not known to cause disease, but can cause undesirable stains, tastes and odours; affect the amount of water a well will produce; and create conditions where other undesirable organisms may grow.

Detecting Iron Bacteria

Clues which indicate that iron bacteria may be present in well water are:

    • Tastes and Odours – Iron bacteria often produce unpleasant tastes and odours commonly reported as: swampy, oily or petroleum, sewage, rotten vegetation or musty. The taste or odour may be more noticeable after the water has not been used for some time. Iron bacteria do not produce hydrogen sulphide, the
      “rotten egg” smell, but do create an environment where sulphur bacteria can grow and produce hydrogen sulphide.
    • Color – Iron bacteria will usually cause yellow, orange, red, or brown stains and colored water.Red Slimy Deposits – Iron bacteria produce a sticky slime which is typically rusty in color, but may be yellow, brown, or grey. A feathery or filamentous growth may also be seen, particularly in standing water such as a toilet tank.

The characteristics listed above are typical of iron bacteria. However, objectionable stains, tastes, or odours may be due to other causes including iron, sulphate, hydrogen sulphide, manganese, or other nuisance organisms such as sulphur bacteria. Identification of substances in water is best done by having a laboratory test a water sample.

Control And Treatment of Iron Bacteria

Treatment techniques may include physical removal, chemical usage or pasteurization. Also, they may prove to be expensive and partially successful. Water softening or oxidation/filtration as well as Shock Chlorination techniques are recommended. Opinion of Water Treatment Experts may be requested and it is also good to evaluate the sanitary quality of water by:

  • Testing the water for nitrate-nitrogen and coliform bacteria
  • Assuring that the well is properly constructed, located, and maintained.



Cullimore D.R. & McCann Annette. 1978 The Identification, Cultivation and Control of iron Bacteria in Ground Water. eds Skinner & Shewan. Aquatic Microbiology Academic Press


Bergey’s Manual of Determinative Bacteriology


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