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The Stainers: Iron & Manganese

Removal: Water Softeners & Iron Removal Filters
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When low to moderate amounts of dissolved iron or manganese are present in water, household water softeners will remove these impurities with the hardness in concentrations determined by the softener manufacturer. The soluble iron and manganese are removed from the water by ion exchange, just as with hardness, and when the water softener is regenerated, the iron, manganese, and hardness will be flushed down the drain.

If some of the iron or manganese is precipitated, it will be filtered out of the water by a softener. However, the gelatinous precipitate tends to stick to the water softening media, gradually building up in the bed. Backwashing the softener usually removes most of the precipitated iron, but some may remain behind. In time, this residue can coat the softening material, gradually reducing the ability of the softener to remove the hardness.

Where the fouling is light, the water softening media can be cleaned periodically with one of the commercial products made for this purpose. Some of these products are also designed to be mixed with the salt so that a mild cleaning occurs with every regeneration. Special salts are also available in which the cleaning materials are blended directly with the salt, so that no other additives are necessary, and the softener is treated with every regeneration.

Where the iron or manganese concentration is too high for a water softener, where much of the iron is already precipitated, or if only iron removal without softening is desirable, iron removal filters are often used. The media in these filters is capable of oxidizing dissolved iron or manganese to the insoluble state and removing the precipitated matter - all in the same tank. These filters must be backwashed periodically to flush the accumulated deposits down the drain, and "regenerated" with potassium permanganate to restore the oxidizing power of the filter media. These iron filters are effective up to reasonably high concentrations of iron and manganese.

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