Iron is one of the most common elements in the Earth's crust, so it is no surprise it finds it way into many home well waters. The maximum contaminant level (MCL) for iron set by the United States Environmental Protection Agency is 0.3 ppm. This can also be expressed as 0.3 milligrams per liter of water. In concentrations above 0.3 ppm, iron in water can cause staining of fixtures and porcelain, ruin laundry, and make the water taste terrible.
Manganese is often found with iron in well water. A bittersweet astringent taste is detectable at concentrations above 0.5 ppm by many people. Manganese causes brown, black and/or tea-color staining, and can impart an asphalt-like or oily taste, above .05 ppm. Some of the same filters used for iron, are used for manganese removal.
If the right sets of conditions are present, a whole house iron filter cartridge can be used in place of the standard backwashing iron filters. These iron filter cartridges cost less than a standard iron filter, but may cost more over a period of a few years, because the cartridges need to be changed frequently. Since they do not require backwashing, they are often used in situations where there is a shortage of well water. They are easier to install than backwashing iron filters and do not require electricity to operate.
Iron and manganese are often found in a dissolved state in well waters, and so your well water may appear clear when first drawn. Upon exposure to air, or after the addition of oxidants (such as air, chlorine bleach or ozone), this clear ferrous iron is oxidized (rusted) to the ferric state to form insoluble particles. A properly designed whole house iron filter will remove both types of iron.
After oxidation or exposure to air, the water then looks orange or yellow. If manganese is present, the water may turn brown or black. This can happen in toilet flush tanks and in the washing machine or dishwasher.
Iron is usually treated with automatic backwashing (self-cleaning) iron filters, which can remove both dissolved and oxidized iron compounds. If sulfur odor is present along with iron, typically chlorine or ozone is fed ahead of an iron filter. In some cases, a backwashing self-cleaning sediment filter can be used in place of an iron filter, if all the iron and manganese has been oxidized to a solid state after the chlorination, ozone injection or air injection process.
There are several different types of backwashing iron filters used, depending on the type and quantity of iron, and the application. Some iron filters, such as the greensand, pyrolox, and Birm filters use a type of manganese oxide media where oxidation takes place right on the filter media as the water passes through it.
Some iron filters use air injection. Often these systems are used after the water has been pretreated with aeration, chlorine or ozone. Birm iron filters work great for iron, but work less well on manganese, and cannot be used where the water contains sulfur odors, chlorine or low pH.
The role of pH is very important in iron treatment. Generally, if the pH of the water is acidic (or less than 7.0), it must be corrected with a special type of neutralizer filter ahead of the iron filtration system. It is usually best to test for pH right at the water source, and not depend on laboratory analysis for pH, since in some cases the pH can raise after sampling, giving false results.
Water softening is sometimes used to remove dissolved iron in low levels (less than 2.0 ppm) although more commonly, we use iron filters in conjunction with water softening if the water is both hard, and high in iron or manganese. Iron is generally not thought of as toxic, although there are some studies that show liver toxicity to men.
A whole house iron filter cartridge contains the same media found in backwashing iron filters (such as Birm, greensand, pyrolox etc). Instead of backwashing and being regnerated, and used over many years, the cartridge is used for a few months and disposed of.
These cartridges work best when the iron in the water is less than 3.0 ppm and the flow rate is less than 10 gallons per minute. For best results, the water should be chlorinated or aerated prior to the whole house filter. If the water comes from a storage tank or cistern then no further aeration is required. While the filters do remove low levels of hydrogen sulfide gas (rotten egg odor) generally it is not a good idea to use these cartridges filters if sulfur odor is present.
While whole house iron filter cartridges are a good choice for many on low flow applications such as summer homes, cottages or mobile homes, they do not replace a well-designed backwashing iron filter. Over a five year period for instance, a backwashing iron filter, which may cost $800 up front, will usually cost less than purchasing a replacement iron filter cartridge every few months for $80 to $100.
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