78Iron
Iron occurs naturally in rocks and soils and is one of the most abundant elements. It occurs in two
forms. Ferrous iron (Fe2) is in a dissolved state, and water containing ferrous iron is colorless.
Ferric iron (Fe3) has been oxidized, and water containing it is rust-colored. Water from some well
sources contains significant levels of dissolved iron, which is colorless, but rapidly turns brown as
air reaches the water and oxidizes the iron.
There are no known harmful effects to humans from drinking water containing iron, but NSDWR
suggest a limit of 0.5 mg/L. At high levels, the staining of plumbing fixtures and clothing becomes
objectionable. Iron also provides nutrient source for some bacteria that grow in distribution systems
and wells. Iron bacteria, such as Gallionella, cause red water, tastes and odors, clogged pipes, and
pump failure.
Whenever tests on water samples show increased iron concentrations between the point where
water enters the distribution system and the consumer’s tap, either corrosion, iron bacteria, or both
are probably taking place. If the problem is caused by bacteria, flushing mains, shock chlorination,
and carrying increased residual chlorine are alternatives to consider.
Manganese
Manganese in ground water creates problems similar to iron. It does not usually discolor the water,
but will stain washed clothes and plumbing fixtures black; this is very unpopular with customers.
Consumption of manganese has no known harmful effects on humans, but the NSDWR
recommend a concentration not to exceed 0.05 mg/L to avoid customer complaints.
Common Water Quality Problems...........
The critical safeguard for water distribution system operations are
continuous positive pressure in the mains; 20 pounds per square inch (psi) minimum
residual pressure is recommended;
maintenance of chlorine residual;
cross-connection control; and
frequent testing.