Iron (Fe) – (Latin: Ferrum) is a chemical element, the second most common metal in the world (after aluminum). In its free form, iron occurs only in meteorites that fall to earth. The presence of iron in groundwater is related to the fact that it is the fourth most common chemical element in nature – it accounts for 4.56% of the mass of the earth’s crust and 8-10% in seawater. In water supply systems the concentration of iron is often higher than the maximum permissible (0.2 mg/L) , and the amount of this parameter in groundwater is often several times higher than the acceptable standard. Even low concentrations of iron in water, such as 0.3-0.4 mg/L can cause the appearance of stains on sinks, dishes, textiles and other surfaces. Elevated levels of iron cause a brownish color, metallic taste and bad odor in water, and can alter the taste and appearance of tea, coffee and other beverages.
Iron is found in all organisms – plants and animals, as a trace element, i.e. in very small amounts (about 0.02% on average). Its main biological function is to transport oxygen. Human daily requirement of iron (6-20 mg) is completely provided by the food we eat (meat, eggs, bread, spinach, beets are rich in iron). The average human body (weight 70 kg) contains 4.2 g of iron, and in one liter of blood – about 450 mg.
This element is most often found in water in dissolved form Fe2+, its removal is based on the oxidation of this element to the form Fe3+ which is insoluble in water. In the next stage of water treatment this compound is retained on suitable filter beds. Other water parameters such as e.g. aggressive CO2, manganese, turbidity, color have a great influence on de-ironing. When designing a technological system, it is required to carry out a complete water test which allows to select the most optimal treatment technology.
