Iron is known to leach into water supplies throughout the United States from rock and soil formations. It has been said, probably an exaggeration, that there is hardly a square foot of soil that does not have some iron content. Iron is at least 5% of the earth's crust.
A yellow to reddish discoloration can appear in water in concentrations as low as 0.3 ppm (parts per million) and begin the staining and scale process, depending on the pH, as well as taste and odor problems.
Five types of Iron that can be found in potable water
Sequestered Iron Sequestering agents are used by municipalities & industry for treatment of large quantities of water. It is not important to farming where private wells are the principal source of water.
Heme iron ?Iron Found in organics This type of iron can not be removed by softening resins. Heme iron is most common in surface water and shallow wells. It is usually a yellow / brown color. Heme iron is a breakdown product of dead vegetation.
The iron and organics (tannins) requires one ppm of sodium hypochlorite and a retention time of 20 to 25 minutes in a pH range of 6.5 - 7.5. Following the oxidation, a filtration media must be used to remove the oxidized iron and the residual of chlorine.
Iron Bacteria Favorable conditions for the growth of Crenothrix, Gallionella, and Clonothrix (or "Iron Bacteria" can exist at very low levels of iron. Oxygen creates an oxidizing energy to precipitate ferrous iron into bicarbonate that is necessary for iron bacteria to exist. This bacterium can now live in a very wide range of conditions.
Iron bacteria water will have a reddish color and an objectionable odor. These organisms's growths cause a jelly like bio-mass. This mass can render media and resin filtration ineffective, reduce the effectiveness of any oxidizing agent, and plumbing fixtures. Iron bacteria is, because of its organic nature, the most difficult to remove and control.
Ozonation is the recommended solution to this problem.
Ferric Iron ?Red water iron In nature iron is usually found in its oxidized insoluble form. Clear water iron, or soluble iron, once exposed to an oxidant or to oxygen will precipitate into an insoluble hydroxide form usually yellowish or reddish in color. This iron while in the clear water state could be removed by softening resins or by activated multi-media filtration. If one use's a 5-25 micron filter it may pack out in a short time and reduce flow and pressure. Changing these filters then become expensive and time consuming. Multi-media filters are more expensive to purchase upfront but the cost per gallon of water filtered is much less and requires little or no time.
Ferrous Iron ?Clear water Iron Sometimes this iron is called ferrous bicarbonate iron. This iron may be removed by a softening resin with a positive charge; however it must be in the invisible soluble form until it is filtered. To prevent the iron from precipitating to its insoluble form frequent regenerations are necessary. If the iron does precipitate, fouling on the resin surface will occur, as well as within the matrix of the bead. This fouling can be minimized by pre-treating the incoming water with an activated carbon filter or by adding chemical cleaners to the brine or potassium regenerate. There are a number of chemical cleaners that will reduce red water iron to clear water iron. These cleaners are necessary when iron levels are high and normally they do not harm the resins. Many filter medias available today oxidize ferrous iron into ferric iron which can then be removed physically.
A yellow to reddish discoloration can appear in water in concentrations as low as 0.3 ppm (parts per million) and begin the staining and scale process, depending on the pH, as well as taste and odor problems.