What is Iron?
It is a metallic chemical element, white, moldable and ductile, it is vital for animal and plant life and is the fourth most abundant element in the earth's crust. Its chemical symbol is Fe, it has an atomic weight of 55.85 gmol / g. This metal is part of minerals such as hematite, magnetite, limonite, pyrite, etc.
The iron in the Water.
Its presence in water is due to corrosion in pipes and storage tanks made of carbon steel containing a percentage of this element. In deep wells, when there is a high concentration of iron, it is due to an excess of iron minerals (such as hematite), which comes into contact with the water.
The iron carbonate reduction reaction in well water is as follows:
FeCO3 + CO2 + H2O –> Fe+2 + 2HCO3–
This is an example of how iron dissolves in water in contact with CO2. This reaction affects pH, consequently high pH increases chlorine precipitation and low pH increases dissolved iron concentration.
Iron concentrations found in water generally do not present a health hazard. However, it can change the taste of water, cause reddish-brown stains on clothing, and lead to problems with buildup in pipes, pressure tanks, and even water softeners.
Bacteria in the iron.
Some types of bacteria get their energy by reacting with the soluble forms of iron and manganese. These organisms are usually found in waters that have high levels of soluble iron. The reaction exchanges the soluble iron into a less soluble form of it, causing precipitation and an accumulation of black gelatinous material (slime). The iron slime masses can clog plumbing and water treatment equipment, as well as break off into clumps that become iron stains in laundries. Bacterial reactions with iron do not cause any additional precipitation compared to exposure to an oxidant. However, the precipitation caused by bacteria occurs more rapidly for that reason it increases fabric dyeing rapidly.
How to treat water to eliminate iron and manganese?
The following processes can be used to retain the manganese dissolved in the water:
- Oxidation (Aeration and chlorination).
- Manganese dioxide catalysts in the presence of an oxidant and filtration.
- pH adjustment.
- Flocculation - Coagulation.