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IRON
Iron is the earth's fourth most abundant element and is commonly found in nearly all water supplies.
When the level of iron in water exceeds the 0.3 mg/L limit, we experience red, brown, or yellow staining of laundry, glassware, dishes and household fixtures such as bathtubs and sinks. The water may also have a metallic taste and an offensive odor. Luckily, high iron levels can be reduced. Although iron can be one of the most frustrating water problems to treat, it can be satisfactorily reduced by using a well designed water treatment system. The first step is to determine which of the many forms of iron exist within the water source.
Once you determine whether you have "clear water", "red water", "organic" or "bacterial" iron in your water, you can take steps to correct the problem.
Keep in mind that no one treatment method will work for every type of iron problem.
Ferrous iron or "clear water" iron
Underground sources of water can cause problems when iron is in its "ferrous" state. Ferrous iron is water-soluble and is the result of carbonic acid reacting with natural iron in the earth's crust. Water affected will appear clear but may have a bloody-metallic taste and odor and cause rust staining on porcelain fixtures.
"Clear water" iron, is the most common form of iron and the one that creates the most complaints by water users. This type of iron is identified after you've poured a glass of cold clear water. If allowed to stand for a few minutes, reddish brown particles will appear in the glass and eventually settle to the bottom
Soluble iron ("clear water iron") is effectively removed by:
Aeration:
Introducing oxygen to the water source to convert soluble iron to its insoluble form.
Water Softener: Removal of soluble iron by ion exchange.
Ozonation:
A specialized form of aeration using ozone to convert soluble iron.
Ion Exchange:
Substituting an acceptable ion (such as sodium) for soluble iron.
Chlorination:
Chemical oxidizer used to convert soluble iron to an insoluble, filterable form.
Manganese Greensand:
An ion exchange sand material which is capable of removing iron. Absorbs dissolved iron and requires chemical regeneration.
Sequestering:
Adding chemical agents to water to keep metals like iron in solution to prevent characteristic red stains.
Ferric iron or "red water" iron
In surface waters from lakes, rivers, ponds, iron usually is in the "ferric" form. Ferric iron is not soluble in water and is the result of ferrous iron coming in contact with oxygen. Ferric iron also appears as the result of deep well water being pumped into a system and then oxygen being introduced to the water.
Ferric iron can cause problems with plumbing, water treatment equipment and can make water look rusty.
When insoluble iron, or "red water" iron is poured into a glass, it appears rusty or has a red or yellow color.
Insoluble iron ("red water iron") is effectively removed by:
Catalytic Filtration "BIRM":
A granular filter medium that enhances the reaction between oxygen and iron and then filters the insoluble iron.
Manganese Greensand:
An ion exchange sand material which is capable of removing iron. Absorbs dissolved iron and requires chemical regeneration.
Filtration:
Media used to entrap and screen out oxidized particles of iron. Usually requires backwashing to remove accumulated iron.
Chlorination:
Chemical oxidizer used to convert soluble iron to an insoluble, filterable form.
Organic iron:
Because iron combines with different naturally occurring acids, it may also exist as an organic complex. A combination of acid and iron, or organic iron, can be found in shallow wells and surface water. Although this kind of iron can be colorless, it is usually yellow or brown. The residue may appear on porcelain fixtures.
Organic Iron is effectively removed by:
Ozonation:
A specialized form of aeration using ozone to convert soluble iron.
Manganese Greensand:
An ion exchange sand material which is capable of removing iron. Absorbs dissolved iron and requires chemical regeneration.
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