Iron and Manganese
Increased content of iron (Fe) and manganese (Mn) in the water affects its characteristic sensory properties (flavor, color, smell). Iron content causes the typical turbidity and rusty iron-taste. Manganese creates oily looking stains on the water surface and brown sediments.
Iron and manganese compounds are present in both surface and underground waters, usually together. Especially underground waters contain such a high concentrations, that their decreasing becomes necessary. Normal concentrations of these compounds are not harmful for human health, but have a significant effect on the hygienic and technological defects as the scaling and clogging of piping, fittings, tanks, boilers and other installations, including a damage to its components.
Iron occurs in groundwater in a form of a soluble divalent ion (the degree of oxidation + II). However, in contact with air, the oxidation state increases and forms the insoluble ferric (+ III) form.
Bivalent form of iron is thus located primarily in groundwater and in the bottom of reservoirs, lakes and wherever the water is not oxygenated. On the contrary, trivalent form can be found in waters containing dissolved oxygen. Manganese is present in water in both dissolved and undissolved forms, mainly in oxidation stage + II + III and + IV. Its most stable soluble form in the groundwater is in the oxidation state + II. In surface waters manganese can be found as insoluble manganese dioxide.
Iron and manganese compounds are preferably removed using the iron and manganese removal equipment with filter material filling which catalyses the reaction of dissolved oxygen, iron and manganese and thereby accelerates the oxidation of the soluble compounds into insoluble. Such insolubles are readily collected and filtered on a filter bed. Regeneration of the filter material takes place only by backwashing with outlet water.