Monday, March 1, 2010

Water Quality Today: Iron


Iron is one of the most troublesome elements in water supplies. Making up at least 5 percent of the earth’s crust, iron is one of the earth’s most plentiful resources. Rainwater as it infiltrates the soil and underlying geologic formations dissolves iron, causing it to seep into aquifers that serve as sources of groundwater for wells. Although present in drinking water, iron is seldom found at concentrations greater than 10 milligrams per liter (mg/l) or 10 parts per million. However, as little as 0.3 mg/l can cause water to turn a reddish brown color.
Iron is mainly present in water in two forms: either the soluble ferrous iron or the insoluble ferric iron. Water containing ferrous iron is clear and colorless because the iron is completely dissolved. When exposed to air in the pressure tank or atmosphere, the water turns cloudy and a reddish brown substance begins to form. This sediment is the oxidized or ferric form of iron that will not dissolve in water.

Iron is not hazardous to health, but it is considered a secondary or aesthetic contaminant. Essential for good health, iron helps transport oxygen in the blood. Most tap water in the United States supplies approximately 5 percent of the dietary requirement for iron.

Taste and Food
Dissolved ferrous iron gives water a disagreeable taste. When the iron combines with tea, coffee and other beverages, it produces an inky, black appearance and a harsh, unacceptable taste. Vegetables cooked in water containing excessive iron turn dark and look unappealing.

Stains and Deposits
Concentrations of iron as low as 0.3 mg/l will leave reddish brown stains on fixtures, tableware and laundry that can be very hard to remove. When these deposits break loose from water piping, rusty water will flow through the faucet.

Iron Bacteria
When iron exists along with certain kinds of bacteria, problems can become much worse. Bacteria feed on the iron, leaving behind a reddish brown or yellow slime that can clog plumbing and cause an offensive odor. This slime or sludge is most noticeable in the tank of the toilet when the lid is removed.

Organic Iron
Iron combines with different naturally occurring organic materials; it may also exist as an organic complex. The combination of naturally occurring organic material and iron can be found in shallow wells and surface water. This type of iron is usually yellow or brown but may be colorless.

Test Your Water
If there is an iron problem with the water supply, the first step is to determine the source. The source of iron may be from the corrosion of iron or steel pipes or other components of the plumbing system where the acidity of the water, measured as pH, is below 6.5.
A lab analysis of water to determine the extent of the iron problem and possible treatment solutions should begin with a test for iron concentration. A water sample kit can be obtained from a certified laboratory. The laboratory’s instructions for collecting the water sample should be followed. Collect the sample as close to the well as possible.
If the source of water is a public water system and you experience iron-related problems, it is important to contact a utility official to determine whether the red water is from the public system or from the home’s plumbing or piping.

Treatment Considerations
 Before choosing a water treatment method or device, answer the following questions:
1. What form of iron do I have in my water system?
2. According to the water test results, will the water treatment unit remove the total iron concentration? (Total iron includes both soluble and insoluble iron.)
3. Will the treatment unit treat the water at the flow rate required for my water system?
4. Will the pH have to be adjusted prior to a particular treatment?
5. Would the construction of a new well or the reconstruction of an existing well be more cost effective than a long-term iron removal treatment process?

Iron water is one of those conditions that will need to be addressed or the long term effects will create additional problems later. Don't put it off.



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