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Whatcom County Health Department
Drinking Water Program, Environmental Health Division
Phone: (360) 676-6724
E-mail: Environmental Health


Iron and Manganese

Iron and Manganese in Drinking Water

This document provides a brief  introduction to treatment options for removing iron and manganese (Fe/Mn) from drinking  water.

Observed Problems:

Iron and manganese occur naturally in geologic formations. They  dissolve into groundwater as acidic rainfall percolates through the soil and rock. In  higher concentrations, iron and manganese cause the following problems:

  • Staining: iron and manganese stain laundry and water use  fixtures.
  • Taste: iron and manganese cause a metallic or vinyl type taste in  the water.
  • Appearance: they will often give an oily appearing,  "crusty" sheen to the water's surface.
  • Sulfur Taste: the same conditions which liberate iron and  manganese underground can liberate hydrogen sulfide from other compounds of the soil or  rock.
  • Clogging: iron and manganese support the growth of iron and  manganese bacteria. These non-health-related bacteria can clog strainers, pumps, and  valves.

Health Effects:

Iron in water is not a health hazard by itself but it may  increase the hazard of pathogenic organisms, since many of these organisms require iron to  grow.

Manganese in large doses causes headaches, apathy, irritability,  insomnia, and weakness of the legs. Long-term heavy exposure may result in a nervous  system disorder.

The Environmental Protection Agency (EPA) has established  "secondary" standards for iron and manganese in drinking water. These limits are  based on aesthetic concerns such as staining, taste and odor, etc. These limits are:

  • Iron = 0.30 mg/L (milligrams per liter or parts per million)
  • Manganese = 0.05 mg/L (milligrams per liter or parts per million)

EPA has not set health standards for either iron or manganese in drinking water. Treatment  is not necessary to remove minor iron and manganese concentrations even if over the  suggested secondary aesthetic limits, unless you are actually experiencing an  objectionable staining problem.

Identifying the type of iron and manganese before choosing a  treatment process:
Iron and manganese come in three different forms that cause the appearance of the water to  range from clear to discolored. Not all treatment methods work on all forms of iron and  manganese. The three forms are:

  1. Your water is totally clear when drawn from the tap: iron/manganese is present in the dissolved form. The terms "clearwater iron and  manganese" or "ferrous" and "manganous", are often used to  describe this form.
  2. Your water is rusty colored when drawn from the tap: when exposed  to oxygen, clearwater iron/manganese will precipitate to form fine brownish (ferric) or  blackish (manganic) "rust" particles.
  3. Your water has a yellow tint, but is totally transparent and the  color does not settle out with time: iron or manganese is probably combined with  organic matter in the water. This is commonly called colloidal iron and manganese. This  form of iron and manganese will not settle out, is too small to be removed by filtration,  and generally will not be effectively treated by a water softener. Colloidal iron or  manganese is very difficult to remove.

Water Quality Tests:
In order to determine which treatment process will work for your particular water quality,  you must know certain water quality factors. Typically important factors for  iron/manganese removal include:

  • the concentration of iron and manganese;
  • the pH (acidity) and hardness;
  • dissolved oxygen for some treatment types (this is a field  measurement); and,
  • the presence of iron and manganese bacteria.

When sampling, be sure to let the cold water run for five minutes  and remove any aerators or filters before taking your sample. Please contact Whatcom  County Health Department at (360) 676-6724 for a list of facilities  that will test your water or refer to the previous page on Contaminants in Drinking Water.

Removal techniques for dissolved iron and manganese (clearwater  form):

  1. Softening: is only recommended where both iron/manganese and  hardness are high. It is effective for water containing less than 2-5 mg/L of dissolved  colorless iron or manganese. Disadvantages: it adds sodium to the drinking water and  creates brine disposal problems.
  2. Filtration Removal: the pH value is critical
  3. Potassium Permanganate Greensand Filtration: pH should preferably be  over 7.5; it is effective for very high levels of iron or manganese.
  4. Catalyst / Oxygen Coated Filter Material: is effective for very high  levels of iron or manganese; uses a Venturi Nozzle to add air to the water.

    Treatment types not recommended:

    • Magnetic iron and manganese devices, electrodialysis, reverse  osmosis, and bag filtration.

For more information:

E-mail us at or call Whatcom County Health Department at (360) 676-6724. Ask to speak to an Environmental Health Specialist in the Water program.

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