Water Softeners
Calcium and magnesium cause hard water, and high
levels can precipitate and clog pipes. The best way to
soften water in household water systems is to use a water
softener unit connected into the water supply line. You
may want to consider installing a separate faucet for
unsoftened water for drinking and cooking. Water
softening units also remove iron.
General Description
The most common way to soften household water is to
use a cation-exchange water softener. Softeners may also
be safely used to remove up to about 5 milligrams per
liter of dissolved iron if the water softener is rated
for that amount of iron removal.
Softeners are automatic, semi-automatic, or manual.
Each type is available in several sizes and is rated on
the amount of hardness it can remove before regeneration
is necessary.
Limitations
Using a softener to remove iron in naturally soft
water is not advised; a green-sand filter is a better
method.
Maintenance
When the resin is filled to capacity, it must be
recharged. Fully automatic softeners regenerate on a
preset schedule and return to service automatically.
Regeneration is usually started by a time clock; some
units are started by water use meters or hardness
detectors.
Semi-automatic softeners have automatic controls for
everything except for the start of regeneration. Manual
units require manual operation of one or more valves to
control backwashing, brining and rinsing.
In many areas, there are companies that provide a
water softening service. For a monthly fee the company
installs a softener unit and replaces It periodically
with a freshly charged unit.
Need for Iron Removal
Iron in the ferric form and manganese will stain
clothes and plumbing fixtures. Ferrous iron is in the
dissolved form and cannot be seen in water. When water
containing ferrous iron is exposed to air, the iron
oxidizes and ferric iron is formed. Ferric iron usually
appears as rust colored particles floating in the water.
Water with a high iron or manganese content is not
considered a health problem, but it can be very
objectionable in taste, odor or appearance. Iron bacteria
are nuisance organisms often associated with soluble iron
in water. Because they cause a slime buildup they can be
quite objectionable. Calcium is an essential nutrient for
this bacteria. The presence of iron bacteria is indicated
by a gelatinous slime on the inside wall of the toilet
flush tank and gelatinous "rusty slugs" being discharged
at the tap. High dosages (200 to 500 milligrams per
liter) of chlorine (known as shock chlorination or
disinfection) are required to control iron bacteria.
Shock chlorination must include the well and system.
General Description
Four types of iron-removal equipment are available:
Iron Filters. Iron filters are only useful for removal
of ferrous iron and manganese; ferric iron will plug
them. They appear similar to water softeners but contain
a bed of natural or synthetic manganese green sand.
Manganese dioxide oxidizes iron and manganese and the
oxidized particles are then filtered out in the lower
part of the bed.
Water softeners. All water softeners will remove
iron; the rating for iron depends on whether the
regeneration will remove the iron from the zeolite or
not. Water softeners contain a zeolite mineral that will
remove soluble iron on an ion-exchange basis (the same
way calcium and magnesium are removed in water
softening). The slime produced by iron bacteria will clog
the zeolite and reduce its effectiveness.
Polyphosphate feeders. These units contain a
phosphate compound which coats the soluble iron and
prevents its oxidation when the water is exposed to air.
The compound is not effective against iron that has
already oxidized.
When some waters are heated, the raised temperature
will reduce the effectiveness of the polyphosphate so
that oxidized iron will accumulate in the water heater.
(Polyphosphate is only effective in cold water. Heating
the water will release the iron.) The heated water will
be rusty and unsatisfactory for home uses.
Chlorination and filter. Chlorination followed by
filtration through a sand filter can remove any quantity
of iron in any form. The chlorine oxidizes and
precipitates the iron and the filter strains out the
particles. Carbon filtration may be required to remove
excess chlorine residue.
This method also destroys iron bacteria. When the
bacteria cannot be permanently eliminated by shock
chlorination, continuous chlorination is required.
Neutralizers
Primary Use This system treats corrosive (acidic)
water. Alkalinity and pH are increased through
processing.
General Description
Passing the water through granular calcite (marble,
calcium carbonate or lime) is the most common method of
home treatment. A mix of calcite and magnesium oxide also
is used. if the water is very acidic or if a high flow
rate is needed, a system to chemically feed soda ash,
sodium carbonate or caustic soda (sodium hydroxide) may
be necessary. These systems increase the sodium content
of water, whereas using calcite or lime increases
calcium.
Disinfection Methods
Chlorination - Both municipal systems and
households can disinfect water by adding chlorine.
Household systems commonly use household bleach.
Chlorination does not remove nitrates or other chemicals,
but may oxidize organics and some minerals such as iron.
Chemical metering devices must be maintained carefully.
Using a carbon filter after chlorination will remove any
excess chlorine and chlorinated chemicals that form.
Other Methods
Other methods of disinfecting water include boiling,
pasteurizing, treating with ultraviolet light, and
treating with ozone. These methods are usually less
practical than chlorination or not readily available.
Note that sterilization (boiling water vigorously for at
least two minutes) kills all organisms. Disinfection
reduces the concentration of organisms to safe levels.
Devices to kill or remove bacteria or viruses are termed
purifiers. Chlorination, distillation, or boiling for 15
minutes are the usual methods used to purify water for
household use.
Disinfection by ozonation or ultraviolet light
methods are replacing chlorination in some water
treatment plants, but are not yet readily available for
home use.
Some filtration units with silver-coated activated
charcoal blocks are being sold for removal or killing of
bacteria. Before purchasing such a unit, evaluate it
carefully and check for sufficient test data and
certification to assure its effectiveness.