granular activated carbon
shubham Inc
(VOC), pesticides and herbicides, as well as chlorine, benzene,
trihalomethane (THM) compounds, radon, solvents and hundreds of other
man-made chemicals found in tap water. Some activated carbon filters
are moderately effective at removing some, but not all, heavy metals.
In addition, densely compacted carbon block filters mechanically
remove particles down to 0.5 micron, including Giardia and
Cryptosporidium, turbidity and particulates. Although some iron,
manganese, and hydrogen sulfide will be removed by these higher
quality activated carbon filters, a manganese greensand iron reduction
filter is generally preferred to remove these contaminants as the
effectiveness of carbon filter against iron and manganese is generally
short-lived if the contaminant concentration is high.
Carbon filters are NOT generally successful at removing dissolved
inorganic contaminants or metals such as minerals/salts (hardness or
scale-causing contaminants), antimony, arsenic, asbestos, barium,
beryllium, cadmium, chromium, copper, fluoride, mercury, nickel,
nitrates/nitrites, selenium, sulfate, thallium, and certain radio
nuclides. Removing these contaminants requires either a reverse
osmosis water filter system or a distiller (some can also be removed
by KDF-55 or manganese greensand).
GAC does not remove sediment / particulate material very well, so they
are often preceded by a sediment filter. Sediment pre-filters also
prolong the activate carbon cartridge life by eliminating gross
contaminants that would otherwise clog the activated carbon thereby
reducing the surface area available for absorption. Carbon block
filters are generally better then GAC filters at removing sediment.
Carbon is a substance that has a long history of being used to absorb
impurities and is perhaps the most powerful absorbent known to man.
One pound of carbon contains a surface area of roughly 125 acres and
can absorb literally thousands of different chemicals. Activated
carbon is carbon which has a slight electro-positive charge added to
it, making it even more attractive to chemicals and impurities. As the
water passes over the positively charged carbon surface, the negative
ions of the contaminants are drawn to the surface of the carbon
granules.
Activated carbon filters used for home water treatment typically
contain either granular activated carbon (GAC) or powdered block
carbon. Although both are effective, carbon block filters generally
have a higher contaminant removal ratio. The two most important
factors affecting the efficiency of activated carbon filtration are
the amount of carbon in the unit and the amount of time the
contaminant spends in contact with it. The more carbon the better.
Similarly, the lower the flow rate of the water, the more time that
contaminants will be in contact with the carbon, and the more
absorption that will take place. Particle size also affects removal
rates.
Activated carbon filters are usually rated by the size of the
particles they are able to remove, measured in microns, and generally
range from 50 microns (least effective) down to 0.5 microns (most
effective).
A typical counter-top or under-the-counter filter system has from 12
to 24 ounces of activated carbon. The most common carbon types used in
water filtration are bituminous, wood, and coconut shell carbons.
While coconut shell carbon typically costs 20% more than the others,
it is generally regarded as the most effective of the three. All of
our activated carbon filters use coconut shell carbon.
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