Chlorination Systems
Chlorine oxidizes the water, turning iron into a solid state, Killing H2S (Bad Odour), and killing all micro-organisms present in the water system.
Iron bound in organics - "Heme Iron"
Iron can also be associated with organics such as tannins. This is also known as organically bound iron or “Heme Iron.” Tannins are very large molecular weight organics that are a breakdown product of dead vegetation. Most common in surface water and shallow wells, tannins can cause water to have a yellow to brown color. These molecules have the ability to hold on to iron by a mechanism called chelation (claw). This type of iron will not be removed by softening resin. To treat for this type of iron, one must treat for the organic and removal by ion exchange (Water Softeners) may not be effective. Oxidation is another process by which tannins can be removed. Sodium Hypochlorite, will oxidize both the tannin as well as the iron. Following the oxidant addition there must be sufficient retention time for the oxidation to occur. The water must than pass through a filtration media (carbon filter) to remove the oxidized iron.
Iron Bacteria
Bacterial iron is actually a microorganism that utilizes ferrous bicarbonate in a metabolic process. In this process the iron is precipitated to its insoluble state and deposited around the cell wall. Crenothrix, Clonothrix, and Gallionella are common types of iron bacteria. Water containing this type of iron will again have a reddish color and may have an objectionable odor. These bacteria can live in a wide range of environmental conditions. Bactericide such as Sodium Hypochlorite (BLEECH) is usually effective in treating for this type of iron.