With respect to Water Pollution, Cause, Effects and Mitigation measures of Iron

Cause:
Iron can exist in water in one of two forms or both. Treatment depends on the form of iron present. Waters containing "ferrous iron" are clear and colorless when drawn. Exposure to air converts ferrous iron into the the insoluble, reddish brown "ferric iron".
Effects:
Iron in water imparts a disagreeable metallic taste. It combines with the tannin in tea, coffee, and alcoholic beverages to produce an unpleasant gray to black appearance. It causes red stains in toilets, plumbing fixtures, tableware and laundry. As little as 0.3 ppm of iron can cause these problems.
Mitigation Measures:
FERROUS IRON - A water softener can remove up to 5 ppm of ferrous iron depending upon size and the type of softener. Very large water softeners can remove up to 10 ppm of iron.
FERRIC IRON - If the water contains considerable ferric iron as evidenced by a reddish brown color, use a sediment filter ahead of the water softener. The sediment filter will remove a portion of the insoluble ferric iron and the water softener the soluble ferrous iron.