How a Water
Softener Operates
Water softeners operate by an ion exchange process. Water
softeners are actually a cation (positively charged ions) exchange
mechanism. Hardness ions are replaced with nonhardness ions. In
order to conduct this procedure, water softeners utilize sodium
(Na+) as the exchange ion supplied from the dissolved sodium
chloride salt, also known as brine. Sodium ions then coat an
exchange medium in the water softener. These exchange mediums are
known as “zeolites” or synthetic resin beads that look like wet
sand.
Calcium and magnesium trade places with sodium ions as the hard
water passes through a water softener. These sodium ions are
replaced by calcium and magnesium ions which enables the free sodium
ions to be released into the water.
A chemical breakdown of the softening process is as follows:
NaZeolite + Ca2 CaZeolite + Na+
and
NaZeolite + Mg2 + MgZeolite + Na+
The exchange medium is coated with calcium and magnesium ions when a
huge quantity of softening has taken place in the hard water. A
recharging or regeneration must occur with the exchange medium. A
softener can be backflushed with a salt brine solution in order to
recharge the softener with sodium ions.
A chemical breakdown of the recharging process occurs as follows:
NaCl + CaZeolite NaZeolite + CaCl
and
NaCl + MgZeolite NaZeolite + MgCl
The hardness of the water, as well as the amount of water utilized,
the size of the unit and the capability of the exchange media to
remove the hardness all factors in determining the amount of time
between the recharging cycles.
The water that is being treated will pass through resin and
negatively charged resins absorb and bind the metal ions, which are
then positively charged. These resins contain univalent sodium ions
and are exchanged with divalent calcium and magnesium ions in the
water to remove the formation of soap scum. Water will pass through
both types of resin and the hardness ions replace the sodium when is
then released into the water. Because of the salt content, many
people believe that soft water should not be ingested. In fact many
local governments will not allow water softeners because of the
concentration of brine solution that accumulates due to the
regeneration process when it gets flushed out of the system and may
then be released into the soil or sewer. As a result, the water
could be detrimental to the environment.
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