Activated Carbon For Drinking
Activated Carbon Filtration FAQ.
*Whole house carbon filters
*Carbon block candle PB1 (with lead reduction)
for Doulton housings.
* Extruded solid carbon block cartridges for
industry standard filter housings and RO membrane.
None Doulton products.
Most Popular Water Purification
Technologies for Domestic Drinking Use (FAQ)
* Doulton Ceramic Technology
* Activated Carbon (AC)
* Granulated Activated Carbon (GAC)
* Extruded Solid Carbon Block (CB)
* Powdered Activated Carbon (PAC)
* Reverse Osmosis (RO)
* Ultraviolet Radiation (UV)
* Ion Exchange (IEX)
* Distillation or Demineralization (DI)
*Absolute vs. Nominal Ratings
What is Activated Carbon?
Activated carbon (AC) is a natural material
derived from bituminous coal, lignite, wood,
coconut shell etc., activated by steam and other
means, and each one have different adsorption
properties (e.g. bituminous carbon for high
chlorine reduction capacity). Some manufacturers
use various blends of carbon to achieve specific
water quality and contaminants reduction (e.g.
coconut shell carbon for "sweet taste").
Activated carbon surface properties are both
hydrophobic and oleophilic; that is, they “hate”
water but “love” oil. When flow conditions are
suitable, dissolved chemicals in water flowing
over the carbon surface “stick” to the carbon in a
thin film while the water passes on.
This process is called adsorption. As a result of
the adsorption process, activated carbon is an
effective method in removing chlorine and it's
by-products (TTHM's) and volatile organic
compounds (carbon based VOC's). Both, man-made and
naturally occurring including among others:
forms of dichloroethylens 1, 2-dechloropropane
xylenes etc., etc.
What other chemicals AC by it's self is
None carbon based anions (-) and cations (+) such
as arsenic, fluorides, some heavy metals, nitrate,
What forms does it come in?
Most popular forms of activated carbon used in
the treatment of POU drinking water filters are
granular activated carbon (GAC), extruded solid
carbon block (CB) and powdered activated carbon
What is granulated activated carbon
All activated carbon forms including granulated
activated carbon (GAC) have a tremendous surface
area resulting from its porous structure. GAC
filters degree of effectiveness depends on the
flow rate of the water and contact time with the
water. If flow rate is excessive their efficiency
could be as low as 0% and if the flow rate is slow
their efficiency can match and or exceed those of
different carbon forms.
For comparative purpose, a teaspoon of activated
carbon have surface area the size of a football
What are the advantages of GAC vs. other
form of carbon?
On a large scale such as municipal water
treatment pools (gravity filters) for taste, odor
and chemical reduction GAC is cheaper, very
effective and can be re-used.
Powdered activated carbon used in CB and PAC
cartridges Fine granule carbon used in GAC
cartridges Coarse mesh carbon used for industrial
and municipal gravity filters
Can I make my own GAC water filter?
Sure. If you are a bit handy you can make a GAC
filter using standard PVC pipe, fittings and few
accessories for less than five dollars. If you
intend to market your "invention" you must apply a
fancy label around the pipe and come up with some
catchy name such as "spring", "natural water",
"pure", something on that order. Kidding, take a
little break from this boring technical stuff
however don't leave, it's getting more interesting
or, for quick and easy to understand the
filtration principle go to Doulton's filtration
Can silver impregnated GAC remove
No form of carbon filter removes bacteria. In
fact under quite normal operating condition all
carbon forms can and do become perfect breeding
grounds for bacteria, including pathogenic
bacteria. Silver based GAC's are effective in
controlling bacterial growth and multiplications
(bacteriostatic) only for a short time because the
silver is in form of a "spray" over a small
percent of granules (usually 1.05% of the total
GAC content). As the water passes the granules
"rub off" each other leaching the silver
prematurely. As we mentioned earlier, a POU filter
containing silver based GAC must register that
device with EPA, that does not mean is approved by
My inexpensive GAC filter is rated for
10.000 gallons while more expensive "block"
filters are only rated for 500 gallons, why are
they so much more expensive?
First of all your 10K filter is rated for
chlorine reduction which if properly designed and
used will do the job for that quantity, a more
expensive "block" filter rates their "life-span"
on specific contaminants reductions such as lead,
THM's etc. It's like comparing apples to oranges.
Granted that you use your 10K chlorine reduction
filter within short time you are fine, otherwise
you are taking chances of bacterial and chemical
What micron pore rating is my GAC filter?
These filters cannot be measured in micron pore
size due to their granular state. They are
measured in mesh size similar to that of your
window screen. Coarse carbon is used in different
applications while in domestic POU finer mesh is
used followed by a cloth like "filter" to prevent
What is "channeling" or "dumping" means?
"Channeling" is water passing through least
resistant path of the granule bed avoiding contact
time with carbon resulting lower effectiveness.
"Dumping" is sudden change in your water pressure
releasing the trapped contaminants into your
glass. "Dumping" can occur also if your carbon
filter media is exhausted (over used). Some times
this is visible as a "gray" water but most often
is not. This phenomenon can also happen with PAC
Sounds like the GAC filters are terrible
Not quite. If your water is municipally supplied
a well designed GAC filter with changeable
cartridge is all you'll need, don't forget to
change the cartridge at least every 6 months.
Avoid those "high capacity" throw away filters
unless you use that capacity within 6-9 months.
Why should I buy expensive carbon block
filter instead of less expensive pitcher-style
or faucet-mounted water filters?
Let me ask you a question. Do you want your
drinking water to be cleanest, semi-clean or just
somewhat clean? Those gadgets are made with small
amount of GAC and ion exchange media. The most
popular pitcher-style "filter" was developed many
years ago in Germany to strip the water from
calcium and magnesium (hardness). Why? In those
days car batteries required periodic refill with
water. The distilled water being so acidic was
eating the lead cells while hard water was
shorting the cells. Of all GAC filters these are
the least effective and cheapest to buy however,
the most expensive to use on ongoing basis (low
capacity "filters"). NSF standard 42 have 3
classes for chlorine reduction; class I is >75%
reduction, class II is 50-75% reduction and class
III is 25-50% reduction. Most of those filters
falls under class III. It's like "you get what you
pay for" rule.
Conclusion: In most cases, pre and
post-filtration, including a ceramic filter
element will improve the effectiveness of the GAC
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Extruded Carbon Block (CB)
Of all carbon forms solid carbon block (CB)
filters are the most efficient and cost effective
method of removing volatile organic carbon
compounds (VOC's, insecticides, pesticides and
industrial solvents) from drinking water.
By adding various ion exchange media (e.g.
zeolite, activated alumina or other media) heavy
metal, MTBE, nitrate and other water treatment
effects can be achieved.
CB's are made of single or various blends of
carbons combined with plastic polymers which are
pulverized to a fine dust then shaped in varieties
of forms under high pressure (600 to 800 tons).
Unlike the other carbon forms, the CB's are
industrial grade filters. They are made in various
sizes and micron ratings (nominal), are physically
strong therefore they do not "channel" nor
"collapse" under pressure change, however they
"dump" if their media is exhausted.
Most 1/2 micron nominally rated CB filters are
effective in cysts and asbestos reduction (not
removal). CB's are the best choice for POU
If used for potable water, pre and or
post-filtration, including a ceramic filter
element, will ensure microbiological protection.
Powdered Activated Carbon (PAC)
Unlike CB's, molded or powdered activated carbon
(PAC) filters are an old carbon technology and is
effective method of removing volatile organic
compounds (insecticides, pesticides and industrial
solvents) from drinking water. These filters are
often mistaken or misrepresent as a solid carbon
Unlike CB's, which use binding material with the
carbon for strength (extrusion), PAC filters are
made of powdered carbon compressed around a
synthetic tube with an outer synthetic or cotton
wrap to hold the powder in place.
As with GAC, PAC filters do "channel" and this
can be observed on a used filter with large yellow
or reddish stains on the white wrap. Those spots
indicate that over time water created erosions
through the powdered cake like filter (when wet).
Water travels through the least resistant path and
the stains are a reaction of chlorine and or iron
with the pre-filter material. Bacteria may also
break down the support media of the filter for
additional nutrients. Some PAC manufacturers
incorporate various ion exchange media for none
carbon based cationic and anionic contaminants
such as arsenic, fluorides, nitrates etc.
As with GAC and CB change these filters often and
do not wait until quality of the water taste has
deteriorated. By this time they have long been
"dumping" contaminants in concentrated level.
NOTE: All POU activated carbon filters should be
used on microbiologically safe water only.
In most cases, pre and or post filtration,
including a ceramic filter element, will improve
the effectiveness of the PAC filter.
One must keep in mind that any water treatment
"filter" media have finite capacity in removing
organic and inorganic compounds for example:
Inorganic arsenic can occur in ground and or
surface waters, and thus in drinking-water, it is
mostly found as trivalent arsenite (As(III)) or
pentavalent arsenate (As (V)). The arsenite form
is several times more toxic (and more difficult to
reduce) than arsenate therefore if your water
source is none chlorinated (chlorine converts As+3
to As+5) look for filter that would remove both
form of arsenic. Cationic and anionic "filters"
capacity are rated on parts per billion (ppb) or
micrograms per liters (µm/L) rather than in
There is a range of water purification products
on the market and there is BelKraft. Effective and
cost efficient drinking water treatment