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Iron Info


Posted by Andy Wilhelm on January 4th, 2003 11:56 PM
In reply to Rust Stains by Andy Wilhelm on January 4th, 2003 11:52 PM [Go to top of thread]

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Here are some details about Iron:
IRON AND MANGANESE
Iron, mostly found in ground water supplies, usually appears in quantities less than 5 parts per million, but occasionally can be found in concentrations as high as 60 ppm. Water containing dissolved "ferrous" iron is usually clear when drawn, but on exposure to air it becomes cloudy, converting the iron to its "ferric" state, which in time, will deposit a rust-colored precipitate stain. The change occurs because oxygen from the air oxidizes the dissolved iron.

Iron in water, at quantities as low as 0.3 ppm, imparts a metallic or astringent taste, and causes rust colored stains on plumbing fixtures, tableware and laundry. Iron combines with tannin in tea, coffee, and alcoholic beverages to produce an unpleasant gray to black appearance. Iron-bearing waters favor the growth of iron bacteria, slime-forming organisms that cause clogging of pipes, and a foul taste and odor.

Manganese, seldom found alone in a water supply, is usually accompanied by iron. Concentrations as low as 0.2 part per million of manganese will produce dark brown or black staining. Fabrics washed in manganese-bearing waters are almost invariably stained. Deposits collect in plumbing, and tap water frequently contains a black sediment and turbidity. Manganese bacteria often causes clogging of pipes.

Because iron appears in different forms and mixes with a variety of other materials, there are a variety of methods of iron removal. A conventional water softener can remove up to 5 ppm of ferrous iron. Specialized water softeners/iron removers, oxidizing and colloidal type iron filters, chlorination and filtration systems, and sediment filters are all effective in reducing iron levels above 5 ppm in given types of water, and are available to meet your specific need.

Oxidizing Type Iron Filters Oxidizing filters can remove up to 10 ppm of both ferric (oxidized) and ferrous (clear) iron. They work well with all types of private water system pressure tanks. Sulphur removal is also possible when levels are 2.0 ppm or less. In cases where both iron and sulphur are present it is suggested that a sediment filter/water softener combination be installed for removal of all iron. The sulphur can then be removed by an oxidizing filter installed after the softener. Oxidizing filters require frequent backwashing and regeneration with a chemical, potassium permanganate. Birm media filters use the oxygen present in the water and eliminate the need for potassium permanganate. Automatic and manual types are available. Do not use oxidizing filters on water supplies that have a pH of 6.8 or less, sulphur in excess of 2.0 ppm or iron amounts exceeding 5 ppm.

Colloidal Type Iron Filters Colloidal filters can remove up to 25 ppm of both ferric (oxidized) and ferrous (clear) iron. It is preferred that they are installed in conjunction with permanent air head type pressure tanks. Colloidal filters are generally backwashed once every 4 days and require no chemicals to regenerate.

They require a water source capable of delivering flows in excess of 5.0 gpm. Successful iron removal is possible within the pH range of 5.5 thru 9.5. Colloidal filters will not work properly on waters that contain tannins or sulphur.

Chlorination and filtration systems This is a means of iron removal that is recommended only when a sulphur, extreme iron bacteria, or taste and odor problem also exists. Use a chemical solution pump to feed chlorine (household bleach) into the line ahead of the pressure tank. Chlorine causes iron in the water to form particles which can be filtered. On low pH waters and acid neutralizing compound should be added to the chlorine solution to facilitate iron removal. Use an activated carbon filter following the pressure tank to remove the iron particles as well as any excess chlorine.

NOTE - THE SUCCESS OF THIS METHOD OF IRON REMOVAL DEPENDS UPON AT LEAST 5 MINUTES OF CONTACT TIME FOR THE CHLORINE TO FULLY REACT WITH THE IRON. THIS CONTACT TIME CAN BE PROVIDED BY A BLENDING TANK SIZED AT A VOLUME OF 4 TIMES THE DRAWDOWN OF THE INSTALLED PRESSURE TANK.

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