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Introduction
Iron
is one of the earth’s most plentiful resources, making up at least five percent of the earth’s crust.
When rainfall seeps through the soil, the iron in the earth’s surface dissolves, causing it to go into almost every
natural water supply, including well water. Although iron is present in our water, it is seldom found at concentrations greater
than 10 milligrams per liter (mg/l) or parts per million (ppm).
Health and Water Quality Iron
is not considered hazardous to health. In fact, iron is essential for good health because it transports oxygen in your blood.
In the United States, most tap water probably supplies less than 5 percent of the dietary requirement for iron. Iron is considered
a secondary or “aesthetic” contaminant. The present recommended limit for iron in water, 0.3 mg/l (ppm), is based
on taste and appearance rather than on any detrimental health effect. Private water supplies are not subject to the rules,
but the guidelines can be used to evaluate water quality. For instance, 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. Water system piping and fixtures can also become
restricted or clogged.
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Types of Iron Iron is generally divided into two main categories: 1) soluble and
2) insoluble. Soluble iron, or “clear water” iron, is the most common form 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. When insoluble iron or “red water” iron is poured into a glass, it appears rusty or has a red or yellow
color. Although not very common in Idaho’s water wells, insoluble iron can create serious taste and appearance problems
for the water user. 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. Finally, when iron exists along with certain kinds of bacteria, problems
can become even worse. The bacteria consume iron to survive and leave a reddish brown or yellow slime that can clog plumbing
and cause an offensive odor. You may notice this slime or sludge in your toilet tank when you remove the lid. 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. Test
Your Water Before you attempt
to remove anything that appears to be iron-related, it is important to have your water tested. A complete water test to determine
the extent of your iron problem and possible treatment solutions should include tests for iron concentration, iron bacteria,
pH, alkalinity, and hardness. If you receive your water from a public water system and experience red water problems, it is
important to contact a utility official to determine whether the red water is from the public system or your home’s
plumbing or piping.
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Well Construction/Reconstruction High
iron levels may be avoided in some cases by changing the screen or casing depth interval of the well as long as the minimum
casing depth requirements are still met. Talking to your neighbors about their well depths and iron levels will give you some
idea of what well depth would pump the lowest amount of iron. It is also helpful to talk to a well driller or pump installer
about local conditions and the cost of drilling a new well in your area. The cost of well work should be compared to the long
term (perhaps twenty years) cost of treating the water for any iron related problems. Treatment When choosing a water treatment method or device, make sure you have answers
to the following five questions: 1. What form of iron do I have
in my water system? 2. Will the water treatment unit remove the total
iron concentration (determined by the water test) in my water supply? (Total iron refers to both soluble and insoluble iron
combined). 3. Will the treatment unit treat the water at the
flow rate required for my water system? 4. Considering the results of
my water test, will this method effectively remove iron? (For example, pH may need to be adjusted before beginning a particular
treatment). 5. Would well construction or reconstruction be
more cost effective than a long term iron removal treatment process?
Treatment considerations for various forms of Iron. Characteristic | Known As | Treatment Methods | Considerations | Drawn tap water is clear and colorless. When allowed to stand,
reddish brown Clear Water particles appear and settle to bottom. | Soluble Clear Water Fe+2 Ferrous Dissolved | Aeration/Filtration | May require lengthy contact
time. Temperature dependent | Water softener | Hardness
must be calculated. System must be airtight. All water must be treated. | Chlorination/Filtration | Chlorine liquid or pellets. Frequent monitoring and proper water
pressure. | Manganese greensand/ Filtration | Requires adequate pressure. | Catalytic filtration “BIRM” | Dissolved oxygen, organic matter, chlorination, polyphosphate,
temperature limitations. | Ozonation | Used
by some municipal systems. Expensive. | Sequestering | May
not prevent staining. You may need to remove the sequestering agents and iron. Test for agents before choosing another treatment device. | Drawn tap water appears rusty or has a red or yellow color. When allowed to stand,
particles settle to bottom. | insoluble Red Water Fe+3 Ferric Oxidized | Manganese greensand/ Filtration | Adequate backwash pressure
required. | Catalytic filtration:
“BIRM” | Dissolved oxygen, alkalinity, organic matter, chlorination, polyphosphate, temperature
limitations. | Chlorination/Filtration | Chlorine liquid or pellets.
Frequent monitoring. Proper water pressure. | Water tank/toilet
tank/plumbing have reddish brown or yellow gelatinous slime or sludge present. May have objectionable odor or oily sheen. | Bacterial
Creno-thrix Leptothrix Gallionella | Shock chlorination and consider following with continuous chlorination. Bactericides. | Shock chlorination should
include; cleaning the well thoroughly, cleaning pump and riser pipe, and complete chlorination and flushing of distribution
system. Make sure bactericides can be used in drinking water. Bactericides need long contact time for adequate treatment. | High color content (yellow or brown) or colorless. Generally groundwater
from shallow well or surface water. | Organic Hemme Tannin | Water
softener | First step is to treat for
organics. Hardness must be calculated. System must be airtight. Treat all water. | Manganese greensand/ Filtration | First step it to treat for
organics. Adequate pressure. | Ozonation | Used by some municipal systems. Expense. |
Aeration: Introducing oxygen to the water source to convert soluble iron to its form. Filtration:
Media used to entrap and screen out oxidized particles of
iron. Usually requires backwashing to remove accumulated iron. Water Softener: Removal of soluble iron by ion exchange. Manganese
Greensand: An ion exchange sand material which is capable
of removing iron. Adsorbs dissolved iron and requires chemical regeneration. Catalytic
Filtration “BIRM”: A granular filter medium that
enhances the reaction between oxygen and iron and then filters the insoluble iron. Ozonation:
A specialized form of aeration using ozone to convert soluble
iron. Ion Exchange: Substituting
an acceptable ion (such as sodium) for soluble iron. Sequestering: Adding chemical agents to water to keep metals like iron in solution to prevent
characteristic red stains. Chlorination: Chemical oxidizer used to convert soluble iron to an insoluble, filterable form. Remember, the type of water you have will determine
what type of treatment is possible. No one treatment technique works for every iron problem and well construction or reconstruction
may be more cost-effective
Ask Mr. Drip: Education Series of Water World Warehouse, Inc. 2007 |
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