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Which Water Purification Systems Are Best? - A Comparison of the Three Most Common Technologies
By C.J.Gustafson
Fresh water is essential to our health and comfort. Not only do we rely on it
to stay hydrated, we use it in many other ways including bathing, cleaning and
cooking food, and laundering our clothes. Fresh water has long been a concern of
both public communities and private individuals, and several different water
purification systems and treatment technologies have been developed to help ensure
that tap water is safe for human consumption. But how do these different
technologies compare?
Whether you get your water from a well or a city system, water sources can
become contaminated by bacteria, runoff, and improper treatment. Even if water
isn’t contaminated, it may contain iron and other hard minerals that cause
discoloration and can build up in the body, or chlorine that leaves an
unpleasant odor and taste. Consequently, many people choose to treat or filter
their water to improve flavor and protect against contaminants.
Chlorine is commonly used by municipal water treatment plants and is effective
in killing many different bacteria. However, it is not effective against some
organisms such as Cryposporidium and Giardia. Both of these organisms can be
found in lakes, rivers, and ground water and can cause serious intestinal
illness.
As mentioned, many people feel that chlorine leaves an unpleasant taste and
smell. In addition, there have been numerous cases where the city water supply
became contaminated despite the fact that it was treated. People with city water
supplies often use other water purifiers and home water filters to ensure that
their water is pure and tastes good. The three most common options are carbon
filters, reverse osmosis water filters, and ultraviolet light water
purification.
Each of these technologies uses a different approach to treat water, and they
each have different levels of effectiveness against various contaminants. One
may work well to remove chemicals but be completely ineffective against
bacteria, and vice versa.
In reality, there is no single filter or treatment that will eliminate every
contaminant from your water. The best approach is to have your water tested for
contaminants and then purchase a home water purifier that guards against the
particular contaminants that cause you concern.
Another option is to combine treatment technologies. Most higher-end systems use
a combination of carbon filters and one of the other treatment technologies to
achieve the best results. Let’s look at the different technologies to see where
each is effective.
Carbon Filters
Carbon is one of the most powerful absorbents available and it has been used for
many years as a means of removing impurities. The absorbing powers of carbon can
be further enhanced by adding a slightly positive electrical charge. This is
known as activated carbon, and it is used in many standard home water filters.
As the water passes over the positively charged carbon, the negative ions of the
contaminants are drawn to the surface of the carbon granules and removed from
the water.
Activated carbon filters typically use granular activated carbon (GAC) or
powdered block carbon. Both work well for filtering and purifying but carbon
block filters have been shown to remove more contaminants. Either type of
activated carbon filters help reduce or remove a wide variety of contaminants,
including:
• volatile organic chemicals (VOCs)
• pesticides and herbicides
• chlorine, radon, and other chemicals often found in tap water.
All of this protection comes in a relatively inexpensive package. You can
purchase carbon filter systems that fit on your faucet for about $30, or you can
choose a whole house water purification system that utilizes carbon filter
technology for around $100.
However, unless they are densely compacted, most carbon block filters are not
effective at removing heavy metals or bacteria. For this reason, many people
consider combining carbon filters with one of the other types of water
purification systems.
Reverse Osmosis Water Filters
Reverse osmosis, also known as hyperfiltration or ultra-filtration, was
developed with U.S. government funding as a means of desalinating ocean water. A
reverse osmosis water purifier uses a semi-permeable membrane that allows pure
water to pass through it, while contaminants are trapped by the tiny pores in
the membrane.
The process requires that the water be pressurized to help force it through the
membrane. Most standard residential water systems have sufficient pressure. Like
activated carbon filters, reverse osmosis also uses charged particles to help
filter out impurities.
The effectiveness of a reverse osmosis water purifier depends on the density of
the membrane. A membrane with larger pores will obviously let larger impurities
pass through. It is also important that the membrane be cleaned regularly for
proper functioning.
Higher quality reverse osmosis water filters use a process known as crossflow to
allow the membrane to continually clean itself. Crossflow directs some of the
water downstream from the membrane, sweeping the rejected contaminants away so
they do not build up and block the membrane.
There are two types of membranes commonly used in reverse osmosis water filters
--Thin Film Composite (TFC) and Cellulose Triacetate (CTA). TFC membranes are
noticeably more effective the CTA membranes but they tend to be less resistant
to the deteriorating effects of chlorine. This problem can be avoided by using
an activated carbon pre-filter to remove the chlorine first.
Reverse osmosis water purifiers come in different sizes and styles including
countertop and whole house water purification systems. They are capable of
filtering out a long list of contaminants including:
• chlorine and other treatment related products
• bacteria
• salts, sugars, proteins
• dyes
• heavy metals
One drawback of reverse osmosis water filters is that they are more expensive
than carbon filter treatment systems, with the average home system costing
around $300. Also, the purification process is usually somewhat slow due to the
use of pressurized water. It can take an entire day to produce 15 gallons of
purified water. And a typical reverse osmosis water purifier may need up to 8
gallons of untreated water to generate a single gallon of purified water.
UV Water Purification
As the name implies, ultraviolet light water purification systems use
ultraviolet (UV) light to treat water and render microorganisms harmless. The UV
light comes from a high intensity lamp that is usually enclosed in a protective
quartz sleeve. When water passes through the water treatment system, the UV
light damages the structure of any organisms and makes them sterile.
Although a UV water purifier requires electricity to operate, it draws about the
same amount of energy as a light bulb. However, the lamp bulb itself needs to be
replaced every year to ensure adequate intensity.
While whole house UV water purification systems are effective on most bacteria,
viruses, molds, algae and other organisms, they do not remove chlorine, heavy
metals, VOCs, or other chemicals. And countertop UV systems, which expose the
water to UV lighting for less time, do not always remove all organisms.
UV water purifiers average around $700 for a whole house system, making them
more expensive initially than other types of treatments. In addition, without a
pre-filter system, contaminants can build up and reduce the intensity of the UV
lamp. For these reasons, many people combine UV water purification systems with
carbon filters, which also increases the costs.
As you can see, each of the three common water treatment technologies has its
advantages and drawbacks. Deciding which is best depends on your budget and the
type of water contaminants you want to remove or prevent. A test of your tap
water will help you determine the appropriate water filtration system for your
needs.
About the Author C.J. Gustafson is a successful writer for http://www.water-filters-n-purifiers.com, providing consumer information on
home water filters
and
water purification systems. She has researched and compared a variety of systems such as
reverse osmosis water filters to help remove iron from her well water.
Copyright 2005 Water-Filters-N-Purifiers.com
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