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Did
you know?
Reverse osmosis is the finest water filtration method known. This process will
allow the removal of particles as small as ions from a solution. It is used
to purify water and remove salts and other impurities in order to improve the
color, taste or properties of the fluid. R.O. uses a membrane that is semi-permeable,
allowing the fluid that is being purified to pass through it, while rejecting
other ions and contaminants from passing.
This technology uses a process
known as crossflow to allow the r.o. membrane to continually clean itself. This
is the reason of why an r.o. element can last many years before clogging or
need replacement. This
water purification process requires a driving force to push the fluid through
the membrane, and the most common force is household water pressure or pressure
from a booster pump. The higher the pressure, the larger the driving force and
efficiency.
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MULTI-MEDIA
WATER FILTERS (Depth Filters)
Multi-media
filters represent a significant improvement over single-media filters.
This is due primarily to improved filter bed action based on the innovative
use and selection of filter media. Multi-media filtration permits delivery
of high quality filtered water at much faster flow rates,
as compared to a conventional sand filter.
In a conventional sand
filter, lighter and finer sand particles are found at the top of the filter
bed, and coarser, heavier sand particles remain at the bottom after backwashing.
Filtration takes place in the top few inches of the filter bed.
The multi-media filter
is radically different. The multi-media filter bed, in comparison to the
sand filter bed, is upside down. Coarse, but lighter, particles backwash
to the top, whereas finer, but heavier, particles remain at the bottom
of the bed. The innovation lies in the selection of suitable media. This
configuration has many advantages. The entire bed acts as a filter, rather
than only the top few inches. Turbidity is trapped throughout the bed,
enabling the filter to hold far more solids filtered from the water before
backwashing is necessary.
Multi-Media Filter Below
Typically, the filter
bed is made up of three layers of filter media. The total bed depth is
about 26 to 40 inches. In a three layer filter the top layer is made up of
large, lighter weight particles of anthracite coal and is from 15 to 18
inches in depth (particle size 1.0 to 1.5 millimeters,
density 1.35 to 1.75). The
middle layer contains from 8 to 15 inches of heavier
and smaller particles of calcined aluminum silicate or sand (particle
size 0.5 to 0.6 millimeters,
density 2.65). The bottom layer contains from 3
to 6 inches of heavier garnet (particle size 0.2 to
0.3 millimeters, density 4.0 to 4.2). This semiprecious red silicate mineral is 50
to 60% heavier than sand.
A multi-media filter
is backwashed in the same manner as a sand filter, using reverse or upward
flow of water through the filter bed. The various layers of media retain
their stratification because each material has a different density.
In
a four-media filter a fourth or top layer contains from 3 to 6
inches of lighter and larger plastic pillows (particle size 2.0
to 4.0 millimeters, density 1.1 to 1.2).
Their density is slightly above the density of water which is 1.0
Advantages
1. The multi-media filter
can operate for much longer periods of time (five or more times as long
at the same filtration rate), before backwashing is necessary because
the bed can hold more turbidity. Turbidity is trapped and held throughout
the entire bed depth, rather than the top one or two inches.
2. Multi-media filtration
is much better suited for use in a closed pressure tank since cracking
of the bed, and subsequent breakthrough of turbidity is virtually eliminated
and the need for visual inspection is unnecessary.
The use of pressure
tanks, rather than open basins or filters, is an obvious advantage for
point-of-use filtration and could also be of real importance in the filtration
of small community water supplies.
More rapid filtration
flow rates in multi-media filtration allow the use
of smaller diameter tanks with equal or better results.
3. A very high degree
of clarity is achieved in the filtered water because of the fact that
the finer particles of garnet at the bottom trap finer turbidity particles.
4. Another
important advantage is that the multi-media filter can clarify water at
a much higher flow rate than a single-media sand
filter (5.5 to 8 gallons per minute, as compared to 1.5 to 2.5 gallons
per minute in a 12 inch diameter tank). This is 14 to 15 gpm per square
foot of bed area, as compared to 2 gpm per square foot of bed area. This
is a very important difference in the production of filtered water.
Central
Systems
In small community
water supply filtration the conventional massive sedimentation tank, which
allows larger particles of turbidity to settle, is replaced by the centrifugal
separator which does the same job in 1 % of the space.
Centrifugal separators
have been used in mining and mineral recovery for many years. Solid particles
entering the separation chamber are acted on by high centrifugal forces
which move the particles to the outer separator walls and then down to
a collection device at the bottom. At the same time the clarified water
moves toward the center of the separation chamber and upward to the clear
water outlet at the top.
Separators can remove
up to 98% of all suspended particles, down to a particle size as small
as three thousandths of an inch (74 micrometers). A human hair has a thickness
of about 100 micrometers.
In the multi-media filter the traditional feed of alum as a coagulant is reduced.
At the same time it is supplemented with a polymer (polyelectrolyte) which
forms a stronger floc and is applicable over a broader turbidity range.
Contact
Clarification
A separate tank, called
a contact clarifier, provides hydraulic contact flocculation and surface
storage clarification. This replaces traditional paddle flocculation and
four hours of quiescent clarification. The sand filter which followed
in the traditional system has been replaced by a more efficient multi-media
filter. Thus, without process shortcuts, process time has been reduced
from the traditional 41/2-6 hours to 8 minutes!
Typical results for
multi-media systems include reduction from 200 NTU to 0.42 NTU on a high
turbidity water, and from 25 NTU to 0.15 NTU on a low turbidity water.
According
to recent news and reports, most tap and well water in the U.S. are not
safe for drinking due to heavy industrial and environmental pollution.
Toxic bacteria, chemicals and heavy metals routinely penetrate and pollute
our natural water sources making people sick while exposing them to long
term health consequences such as liver damage, cancer and other serious
conditions. We have reached the point where all sources of our drinking
water, including municipal water systems, wells, lakes, rivers, and even
glaciers, contain some level of contamination. Even some brands of bottled
water have been found to contain high levels of contaminants in addition
to plastics chemical leaching from the bottle.
A good water
filtration system installed in your home is the only way to proactively
monitor and ensure the quality and safety of your drinking water. Reverse
osmosis water purification systems can remove 90-99% of all contaminants
from city and well water to deliver healthy drinking water for you and
your family.
Healthy and Convenient!
Our Featured Reverse Osmosis Drinking Water System
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