Iron in
water can cause plumbing and laundry stains in as little
as 0.3 parts per million
In its soluble forms iron can form sludge deposits in
pressure tanks, pipe lines, water heater coils and other
plumbing fixtures.
Iron may be present in water as:
-
Soluble ferrous ions
-
Ferric ions, soluble in very acidic water
-
Ferric hydroxide, insoluble in neutral or alkaline
water
-
Ferric oxide, which show up as particles of rust
in pipes
-
In combination with organic compounds or iron
bacteria
frequently when iron is drawn to the surface, it
occurs in the soluble ferrous state, upon exposure to
the air, molecular oxygen begins to enter the water as
carbon dioxide escapes. The oxygen then oxidizes the
ferrous ions changing then to ferric ions. At this point
the ferric ions combine with free hydroxyl ions (OH-) to
form the insoluble gelatinous compound ferric hydroxide.
As the individual molecules join together,
characteristic rust color (often called "red water'
or "rusty water") appears. And finally a
gelatinous precipitate of ferric hydroxide settles to
the bottom of the container, in this way the soluble
ferrous ions convert into the insoluble ferric
hydroxide.
When iron is found in surface supplies, the water may
well be extremely acid, or the iron may be combined in
various complex molecules which resist oxidation.
In some surface waters iron may be present in an
organic (gelated0 form. Such water usually contains a
great deal of color.
Iron bacteria frequently thrive in iron-bearing
water. As they develop, these bacteria form
reddish-brown growths which may clog pipes and reduce
flow rates. A decaying mass of these iron bacteria can
cause bad tastes and odors in a water supply, as well as
severe discoloration problems.
