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Treatments to Purify
Your Drinking Water
The Latin expression
“aqua pura, aqua vitae” can be translated as “pure water, living water,”
or “pure water is the water of life.” Water is the mater (mother) and
matrix (container, structure, or medium) of life.
No water, no life; life cannot exist
without water. Today water in its raw state is not suitable for
drinking, as it contains numerous contaminants that are know to be
dangerous to human health and all living things. If it is too acidic, it
can also be harmful to inorganic materials like soil and stone.
While scientific advances have created many of our problems with water,
scientific advances are now working to solve them. New devices are being
invented to heal aqua ailments, which in turn will safeguard our health
and the health of our crops and animals and even the soil itself.
Wonderful devices are available to purify tap water and make it taste
like nectar. Ordinary tap water can be made suitable for drinking.
Pure water is essential to healthy living. Ordinary tap water, even
though treated by the supplier, contains numerous contaminants,
including bacteria, algae, fungi, viruses, minerals, and chemicals. A
water purifier will remove these organisms and contaminants to make the
water fit to drink. Water purifiers save us from potential bacterial and
viral diseases that can easily spread through contaminated water.
Water Purification Techniques
Different types of water purifiers use different techniques. Common
techniques include boiling, distilling, carbon filtering, reverse
osmosis, ion exchange, electrode ionization, water conditioning, and
plumbo-solvency reduction.
Carbon filters are commonly used in home water systems. Charcoal, a form
of carbon, absorbs many contaminants due to its high surface area and
mode of preparation. As the water passes through the activated charcoal,
contaminants are removed by one of two carbon filtering systems:
granular charcoal filtering or submicron solid-block carbon filtering.
Granular charcoal is not as effective as submicron carbon filtering for
removing contaminants such as mercury, asbestos, volatile organic
chemicals, pesticides, disinfection by-products (the trihalomethanes),
MTBEs, PCBs, and similar substances. The submicron solid-block carbon
filter removes all contaminants.
Home water filters for drinking water sometimes contain silver. Small
amounts of silver ions released into the water have a bactericidal
effect.
In reverse osmosis, mechanical pressure is applied to a contaminated
solution to force it through a fine, semipermeable membrane that will
only allow water molecules to pass through, thus trapping the
contaminants on one side and ensuring clean water on the other. It is
said to be the most thorough method of large-scale water purification.
Ion exchange is another technique used in water purification. Most
common ion exchange systems involve a zeolite resin bed. Unwanted Ca2+
and Mg2+ ions are simply replaced with soap-friendly Na+ or K+ ions. A
more stringent type of ion exchange exchanges H+ ions for unwanted
cations and hydroxide (OH-) ions for unwanted anions. The result is H+ +
OH- + H2O. This system is recharged with hydrochloric acid and sodium
hydroxide, respectively, resulting in deionized water.
Electrodeionization involves passing the water through a positive
electrode and a negative electrode. Ion-selective membranes make the
positive ions separate from the water and move toward the negative
electrode and make the negative ions move toward the positive electrode.
This technique results in deionized water of a high purity. Before
electrodeionization, the water is usually passed through a reverse
osmosis unit to remove organic contaminants and debris.
Hard water conditioning reduces the effects of minerals dissolved in
water. Hardness salts become deposited in water systems subject to
heating because of the decomposition of bicarbonate ions, which creates
carbonate ions that crystallize out of saturated solutions of calcium or
magnesium carbonate. Water with high amounts of hardness salts can be
treated with soda ash (sodium carbonate) to precipitate out the excess
salts through the common ion effect. The precipitated calcium carbonate
is of a very high purity and is traditionally sold to toothpaste
manufacturers.
Plumbo-solvency reduction is used in areas with naturally acidic waters
of low conductivity, such as surface rainfall in mountains of igneous
rocks, that are capable of dissolving the lead in lead pipes. Small
quantities of phosphate ions are added and the pH is slightly increased.
This greatly reduces plumbo-solvency by coating the inner surfaces of
the pipes with insoluble lead salts.
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