Iron and Manganese in Drinking
This document provides a brief introduction to treatment options
for removing iron and manganese (Fe/Mn) from drinking water.
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
- 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.
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
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
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:
- 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.
- 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"
- 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
- the concentration of iron and manganese;
- the pH (acidity) and hardness;
- dissolved oxygen for some treatment types (this is a field
- 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
- 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.
- Filtration Removal: the pH value is critical
- Potassium Permanganate Greensand Filtration: pH should preferably
be over 7.5; it is effective for very high levels of iron or
- 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 email@example.com
or call Whatcom County Health Department at (360) 676-6724.
Ask to speak to an Environmental Health Specialist in the Water
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