- Water Purification
- a process which removes specified contaminants from
a water source.
- Water Disinfection - a purification
process which kills or removes biological
contaminants such as cysts, bacteria, viruses,
protozoa, etc. from a water source.
- Water that has been disinfected may still
be polluted with contaminants that are not
affected by the disinfection treatment.
- In some cases, additional contaminants may
actually be added to the water during the
- For instance, the process of chlorination
nearly always adds some disinfection byproducts.
- Boiling water will actually concentrate
Granular Activated Carbon Filters (GAC):
Activated carbon is particles of carbon that have
been treated to increase their surface area and increase
their ability to adsorb a wide range of contaminants -
activated carbon is particularly good at adsorbing
Contaminant reduction in GAC filters takes place by two processes: physical removal of contaminant particles, blocking those that are too large to pass through the pores (obviously, filters with smaller pores are more effective). There is also a process called adsorption by which a variety of dissolved contaminants are attracted to and held (adsorbed) on the surface of the carbon particles. The characteristics of the carbon material (particle and pore size, surface area, surface chemistry, density, and hardness) influence the efficiency of adsorption.
GAC is a highly porous material; therefore, it has an
extremely high surface area for contaminant adsorption.
One reference mentions "The equivalent surface area of 1
pound of GAC ranges from 60 to 150 acres (over 3
football fields)." Another article states, "Under a
scanning electron microscope the activated carbon looks
like a porous bath sponge. This high concentration of
pores within a relatively small volume produces a
material with a phenomenal surface area: one teaspoon of
activated carbon would exhibit a surface area equivalent
to that of a football field.
GAC is made of tiny clusters of carbon atoms stacked
upon one another. The carbon source is a variety of
materials, such as peanut shells, coconut husks, or
coal. The raw carbon source is slowly heated in the
absence of air to produce a high carbon material. The
carbon is activated by passing oxidizing gases through
the material at extremely high temperatures. The
activation process produces the pores that result in
such high adsorptive properties.
back to top
The adsorption process depends on the following 5
- Physical properties of the GAC, such as pore
size distribution and surface area
- The chemical nature of the carbon source
(the amount of oxygen and hydrogen associated with
- Chemical composition and concentration of the
- The temperature and pH of the water
- The flow rate or time exposure of water to GAC
It is important to replace the cartridge according
to the manufacturer's instructions.
Advantages of GAC filters:
- GAC filters are used for aesthetic water
treatment, since they can reduce chlorine and
particulate matter as well as improve the taste and
odor of the water.
- Loose granules of carbon do not restrict the
water flow to the extent of Solid Block Activated
Carbon (SBAC) filters, which makes them suitable in
situations, like whole house filters, where
maintaining a good water flow rate and pressure is
- Simple, economical maintenance. Typically an
inexpensive filter cartridge needs to be changed
every few months to a year, depending on water use
and the manufacturer's recommendation.
- GAC filters do not require electricity, nor do
they waste water.
- The bottom line is that GAC filters are effective and valuable water treatment devices, but their limitations must be considered. A uniform flow rate, not to exceed the manufacture's specifications, needs to be maintained for optimal performance and the filter cartridge must be changed after treating the number of gallons the filter is rated for.
Ultra Violet Light:
Water passes through a clear chamber where it is exposed
to Ultra Violet (UV) Light. UV light effectively
destroys bacteria and viruses. However, how well the UV
system works depends on the energy dose that the
organism absorbs. If the energy dose is not high enough,
the organism's genetic material may only be damaged
rather than disrupted.
Advantages of using UV:
- No known toxic or significant nontoxic
- Removes some organic contaminants
- Leaves no smell or taste in the treated water
- Requires very little contact time (seconds
versus minutes for chemical disinfection)
- Improves the taste of water because some organic
contaminants and nuisance
- Microorganisms are destroyed
- Many pathogenic microorganisms are killed or
- Does not affect minerals in water
Disadvantages of using UV:
- UV radiation is not suitable for water with high
levels of suspended solids, turbidity, color, or
soluble organic matter. These materials can react
with UV radiation, and reduce disinfection
performance. Turbidity makes it difficult for
radiation to penetrate water and pathogens can be
'shadowed', protecting them from the light.
- UV light is not effective against any non-living
contaminant, lead, asbestos, many organic chemicals,
- Tough cryptosporidia cysts are fairly resistant
to UV light.
- Requires electricity to operate. In an emergency
situation when the power is out, it will not work.
- UV is typically used as a final purification
stage on some filtration systems. If you are
concerned about removing contaminants in addition to
bacteria and viruses, you would still need to use a
quality carbon filter or reverse osmosis system in
addition to the UV system.
back to top
The formation of oxygen into ozone O3 occurs with the
use of energy. This process is carried out by an
electric discharge field as in the CD-type ozone
generators (corona discharge simulation of lightning).
Ozone is a naturally occurring component of fresh
air. It can be produced by the ultraviolet rays of the
sun reacting with the Earth's upper atmosphere (which
creates a protective ozone layer), by lightning or it
can be created artificially with an ozone generator.
The ozone molecule contains three oxygen atoms
whereas the normal oxygen molecule contains only two.
Ozone is a very reactive and unstable gas with a short
half-life before it reverts back to oxygen. Ozone is the
most powerful and rapid acting oxidizer man can produce,
and will oxidize all bacteria, mold and yeast spores,
organic material and viruses given sufficient exposure.
In the home, ozone is often combined with activated
carbon filtration to achieve a more complete water
Advantages of using Ozone:
- Ozone is primarily a disinfectant that
effectively kills all biological
- Ozone also oxidizes and precipitates iron,
sulfur, and manganese so they can be filtered out of
- Ozone will oxidize and break down many organic
chemicals including many that cause odor and taste
- Ozonation produces no taste or odor in the
water. Since ozone is made of oxygen and reverts to
pure oxygen, it vanishes without a trace once it has
Disadvantages of using Ozone:
- Ozonation requires electricity to operate. In an
emergency situation when the power is out, it will
- Ozone is not effective at removing dissolved
minerals and salts.
back to top
In an emergency, boiling is the best way to purify water
that is unsafe because of the presence of protozoan
parasites or bacteria.
If the water is cloudy, it should be
filtered before boiling. Filters designed for use when
camping, coffee filters, towels (paper or cotton),
cheesecloth, or a cotton plug in a funnel are effective
ways to filter cloudy water.
Place the water in a clean container and bring it to
a full boil and continue boiling for at least 3 minutes
(covering the container will help reduce evaporation).
If you are more than 5,000 feet above sea level, you
must increase the boiling time to at least 5 minutes
(plus approx. one minute for every additional 1,000 feet)
Boiled water should be kept covered while cooling.
Advantages of Boiling Water:
- Pathogens that might be lurking in your water
will be killed if the water is boiled long enough.
- Boiling will also drive out some of the Volatile Organic Compounds (VOCs) that might also be in the water. This method works well to make water that is contaminated with living organisms safe to drink, however because of the inconvenience, boiling is not routinely used to purify drinking water except in emergencies.
Disadvantages of Boiling Water:
- Boiling should not be used when toxic metals,
chemicals (lead, mercury, asbestos, pesticides,
solvents, etc.), or nitrates have contaminated the
- Boiling may concentrate any harmful contaminants
that do not vaporize as the relatively pure water
vapor boils off.
- Energy is needed to boil the water
back to top
In many ways, distillation is the reverse of boiling. To
remove impurities from water by distillation, the water
is usually boiled in a chamber causing water to
vaporize and the pure (or mostly pure) steam leaves the
non-volatile contaminants behind. The steam moves to a
different part of the unit and is cooled until it
condenses back into liquid water. The resulting
distillate drips into a storage container.
Salts, sediment, metals - anything that won't boil or
evaporate - remain in the distiller and must be removed.
Volatile organic compounds (VOCs) are a good example of
a contaminant that will evaporate and condense with the
water vapor. A vapor trap, carbon filter, or other
device must be used along with a distiller to ensure the
more complete removal of contaminants.
Advantages of Distillation:
- A good distillation unit produces very pure
water. This is one of the few practical ways to
remove nitrates, chloride, and other salts that
carbon filtration cannot remove.
- Distillation also removes pathogens in the
water, mostly by killing and leaving them behind
when the water vapor evaporates.
- No drop in quality over time - As long as the
distiller is kept clean and is working properly the
high quality of treated water will be very
- No filter cartridges to replace, unless a carbon
filter is used to remove volatile organic compounds.
Disadvantages of Distillation:
- Distillation takes time to purify the water. It
can take two to five hours to make a gallon of
- Distillers uses electricity all the time the
unit is operating
- Distillers remove all of the oxygen from the
- Distillers require periodic cleaning of the
boiler, condensation compartment, and storage tank.
- Countertop Distillation is one of the more
expensive home water treatment methods, using $0.25
to $0.35 of electrical energy per gallon of
distilled water produced - depending on local
electricity costs. The cost of ownership is high
because you not only have the initial cost of the
distillation unit to consider, but you also must pay
for the electrical energy for each gallon of water
produced. If it cost you $0.25 to distill each
gallon and you purified 10 gallons per week, you
would pay $130 for your 520 gallons of distilled
water each year.
- Most home distillation units require
electricity, and will not function in an emergency
situation when electrical power is not available.
back to top
Reverse Osmosis (RO):
Osmosis is a separation process which uses water
pressure to force water molecules through a membrane
that has extremely tiny pores, leaving the larger
contaminants behind. Purified water is collected from
the "clean" side of the membrane, and water containing
the concentrated contaminants is flushed down the drain
from the "contaminated" side. This is the reverse of the
"normal" osmosis process, where water moves naturally .
. . through a semi-permeable membrane . . .
from an area of low solute concentration . . . to an
area of high solute concentration (with no external
The average RO system is a unit consisting of a sediment/chlorine pre filter, the reverse-osmosis membrane, a water storage tank and an activated-carbon post filter. They cost approx. $150 to over $1,500 for point of use systems.
Advantages of Reverse Osmosis:
- Reverse osmosis significantly reduces salt, most
other inorganic material present in the water, and
some organic compounds. With a quality carbon filter
to remove any organic materials that get through the
filter, the purity of the treated water approaches
that produced by distillation.
- Microscopic parasites (including viruses) are
usually removed by properly functioning RO units,
but any defect in the membrane would allow these
organisms to flow undetected into the "filtered"
water - so they are not recommended for use on
biologically unsafe water.
- Though slower than a carbon or sediment water
filter, RO systems can typically purify more water
per day than distillers and are less expensive to
operate and maintain.
- Reverse Osmosis systems also do not use
electricity, although because they require
relatively high water pressure to operate, they may
not work well in some emergency situations.
Disadvantages of Reverse Osmosis:
- Point of Use RO units make only a few gallons of
treated water a day for drinking or cooking.
- RO systems waste water. Two to four gallons of
"waste" water are flushed down the drain for each
gallon of filtered water produced.
- Some pesticides, solvents and other volatile
organic chemicals (VOCs) are not completely removed
by RO. A good activated carbon post filter is
recommended to reduce these contaminants.
- Many factors impact the RO membrane's efficiency
in reducing the amount of contaminant in the water.
These include the water's pH, temperature and
pressure; the contaminant's concentration and
chemical properties as well as the membrane type and
- Although RO filters do not use electricity, they
depend on a relatively high water pressure to force
the water molecules through the membrane. In an
emergency situation where water pressure has been
lost, these systems will not function.
- RO systems require maintenance. The pre and post
filters and the reverse osmosis membranes must be
changed according to the manufacturer's
recommendation, and the storage tank must be cleaned
- Damaged membranes are not easily detected, so it
is hard to tell if the system is functioning
normally and safely.
back to top
Atmospheric Water Generators (AWG):
Atmospheric Water Generators represent an incredible technological breakthrough. Everest Water AWG machines create pure, fresh drinking water out of the air we breathe. AWG units are humidity and temperature driven; meaning the higher the humidity in the atmosphere the more water the machine will produce. Humidity is part of the earth’s hydrologic cycle. The water that is produced by the AWG converting moisture in the air to water contains no contaminates, bacteria or other microorganisms.
Everest Water patented EnviroGuardTM purification system uses Ozone and GAC filters to ensure 100% pure water at all times. Everest AWG units carry the name
"YETI"1 for branding and customer awareness.
1(The YETI, a mountain snowman that is said to inhabit Mount Everest and is known and recognized worldwide, hence allowing Everest Water product recognition.)
How Atmospheric Water Generators work
- The Everest AWG first pulls air through an
electrostatic filter, removing 99% of all air born
- A condensation unit receives this clean humid
airflow and condenses water vapor into liquid.
- As the machine collects the water, it drops into a
collection tank where it is immediately Ozonated to kill
all bacterial contaminates.
- The entire tank is chilled and this cool refreshing
water is then pumped through a granulated activated
carbon (GAC) filter which filters out any excess Ozone
and makes the water taste great.