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Iron in Water Where can I find information about Iron in water?Iron
Iron is one of the most common elements found in the earth's crust and most water supplies contain
at least a small amount. It becomes a problem when its concentration reaches 0.3 mg/L in a water supply.
Iron can be present in two states: ferrous - Fe+2 (dissolved) and ferric - Fe+3 (extractable).
Dissolved iron is the water soluble form and is colourless in freshly-pumped water. It will convert to the extractable form in the
presence of air. This explains why water which at first appears clear will turn yellowish or brownish in colour.
Extractable iron is reddish or brownish in colour and, if present in a water supply, will discolour
the water. Extractable iron is also present in sediment particles. Therefore, water containing clay, silt or sand will show irondiscolouration.
Other potential problems caused by high iron are discolouration of laundered goods, stains on plumbing
fixtures, stains on dishes and utensils, deposition of a slimy coat inside pipes and a bitter, harsh or sweet taste to water or beverages.
High iron is not normally considered a health hazard as iron is required in a normal human diet. The
limit of 0.3 mg/L has been established for aesthetic reasons, on the basis of its effects on plumbing, laundry, taste and other household uses.
Treatment
An iron problem may have several solutions. If ferric iron (mainly in the form of sediment) is the cause, the following may prove helpful:
- Heavy pumping for a minimum 12-hour period.
- Lowering or raising the pump intake by at least 10 feet.
- Installing a sediment filter.
- Reconstructing the old well or drilling a new well. This usually involves adding more casing.
- Chemical treatment using the process of oxidation, precipitation, chlorination and filtration. This requires the purchase of fairly
expensive equipment.
If ferrous (dissolved) iron is the cause, the following methods may be helpful:
- Installing an ion exchange domestic water softener (for concentrations less than 5 mg/L only).
- Chemical treatment using the process of oxidation, precipitation, chlorination and filtration.
Charlottetown
Jones Building
Robison, Alan (Senior Drinking Water Technologist)
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