Most Popular Water Purification Technologies for Domestic Drinking Use
With so many choices of purifiers and filters on the market. Where do I start?
Start by reading about Doulton ceramic technology
and various other technologies currently in use. This will familiarize you with the different technologies available to treat
your water. Next, go to our Product Selector and follow the
steps. Of course, you can always feel free to contact us (firstname.lastname@example.org).
We will make some recommendations to you based on your water supply and
Before purchasing a drinking water device determine which contaminants you want
to remove, are these contaminants in your water, the degree of "purity"
of the water etc. as there is no such a device or technology that "does
Which point of use (POU) technologies other than Doulton are currently used
in domestic water filtrations?
The most popular and economical method is Activated Carbon (AC). Other technologies are Reverse Osmosis (RO), Ultraviolet
Radiation (UV), Ion Exchange (IEX) and Distillation or Demineralization (DI).
Are there more effective technologies other
than the above mentioned such as EPA certified?
First of all, technologies are based on their physical
properties and scientific facts that can be easily understood.
Second, EPA does not certify POU water treatment devices.
In U.S. any device containing man made or natural "purifier"
such as iodine, chlorine, silver or copper oxides, "food grade" pesticides
etc. must register that device
Stay clear of the products that you cannot understand how they work
pseudo scientific (vague) terminologies such as; "pre
coat technology", "FDA approved", "molecular sieving
"redox technology", "alkalizer", "NASA technology", "EPA
certified purifier", "patented" or other mysterious "technologies".
What are the certification standards and who sets those standards for POU filtration devices?
The certification standards vary from region to region and some parts
of the world don't have any. The certification standards are set by governmental
institutions, industries associations and or combination of both. For
example ISO (International Standard Organization, Zurich, Switzerland)
sets world standards in manufacturing procedures (toughest to achieve
and maintain), while in U.S., ANSI (American National Standard Institute)
set standards. For example: In US for food equipment and POU devices NSF
in collaboration with ANSI write standards that will meet EPA and FDA
guidelines. NSF standards for POU filtration devices are 42, aesthetic
contaminants (chlorine reduction) and 53, health related contaminants
(cysts and turbidity reduction).
What is the difference between "tested by NSF" filter and a filter
"tested to NSF standard"?
None. One was tested by NSF laboratory or their subcontract labs while
the second one opted for less expensive ANSI accredited laboratory e.g.
Underwriter Laboratories etc. One have to keep in mind that all those
tests cost thousands of dollars.
Which POU technology remove most contaminants out of the water?
"Contaminants" is a very general term which determines the use of treated
water. For everyday drinking and cooking water a well designed activated carbon
block is best in removing chlorine and it's by-products, pesticides, herbicides,
carbon based industrial chemicals as well organic pharmaceuticals. In addition
to good carbon block incorporates ion exchange media to remove heavy metals
such as lead. Carbon block does not remove "contaminants" such as
calcium, magnesium, potassium and other natural minerals which contributes
to fresh, spring like thirst quencher.
A well designed and maintained distiller, laboratory grade*
RO systems maintained and periodically tested by a qualified technician
using high quality pre-treated water (*not
to be confused with inexpensive domestic RO systems commonly sold in
big box stores or by softeners salesman).
I am specifically concerned about removing parasitic cysts like cryptosporidium
and giardia from my water. What is the best filtration or purification method for cysts?
Generally cysts size in range from about 3-7 microns and can be reduced by fine filters however
to completely remove 100% a filter pore size have to be at least 1 micron absolute with greater than 99.99% efficiency.
Many filters on the market claim cysts reduction using surrogates (AC fine test dust in 0.5-3 micron size range) test standards vs. live cysts method
which is tougher and more accurate test.
For immunocompromised individuals the following POU labeled devices may or may not remove Cryptosporidium.
|POU device labeled only with these words may not be designed to remove Crypto
||POU device labeled with these words indicate should be able to remove Crypto
- Pore size of 1 micron or 1/2-micron filter
- Effective against Giardia
- Effective against parasites
- Carbon filter, water purifier or softener
- EPA approved - EPA does not approve or test filters
- EPA registered - EPA does not register filters for Crypto removal
- Activated carbon, removes chlorine
- Ultraviolet light or UV purifier
- Reverse-osmosis (without NSF testing)
- Pentoidine resins, bacteriostatic
- Reverse-osmosis tested to ANSI/NSF 53 for cyst removal, ask
- Absolute pore size of 1 micron or smaller (w/>99.99% efficiency 4 log test standard protocol), ask for results
- Tested with live crypto cyst and certified to NSF Standard 53 for cyst removal, ask for results
NOTE: There is general misconception even among medical professionals recommending reverse-osmosis not understanding operational and maintenance requirements of such POU device to be able to remove Crypto.
Most all carbon filters are in particulate reduction range.
and RO manufacturers often "claim" that natural minerals in
water are not beneficial for you while POU manufacturers "claim"
the opposite. Who's right?
Our view is that we should rely on minerals through food intake rather
than water. On the other hand have you ever tried "pure" water?
It's flat and lifeless, taste stale and is very acidic. Laboratory water
should be "pure". Drinking water should be safe and wholesome,
free from pathogenic bacteria and chemicals, full of oxygen and mineral content that gives water spring-like taste and freshness.
Should you opt for "pure" drinking water then distilled water is much "purer" than reverse osmosis water even under best RO performance conditions.
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Reverse osmosis (RO) is a membrane filtration process separating dissolved
salts from a water stream. In RO, not only are insoluble particles rejected
by the membrane but also molecules and ions in solution. Concentration
of ions near the membrane sets up ‘polarization’ phenomena which results
in an increase in the osmotic pressure of the solution to be treated,
sometimes followed by precipitation. The continuing flow of input water
under high pressure (>200 psi) flushes
the membrane, which removes the ion concentrations and/or precipitates.
are not normally "water efficient" and wastewater rejected by
the system may be significant. Purchase and installation costs can be
significant. RO membrane are notoriously prone to scale and bacterial build-ups and ruptures.
Slime-forming bacteria can cause rapid deterioration of performance. If you own a Doulton filter you'll know what "slime-forming bacteria" is. When you clean the ceramic candle it is the pinkish slippery bio-film that built up on the surface slowing your filter flow rate.
Due to various factor that can affect membrane performance a major
membrane manufacturer have the following statement in red letters imprinted
on the packaging: "Do not rely on this mambrane for Cryptosporidium or
Giardia cyst removal".
High end laboratory RO systems rejects high degree of organic
and inorganic compounds producing high quality pharmaceutical grade
water. To achieve this producers pre-treat the water using various pre-treatment
methods such as passing through pre-filters, ion exchange resin beds
etc. Under right pressure (>200 psi.) and temperature
the pre-treated water is then pumped through two RO membranes connected
in series (double pass) rejecting dissolved compounds in molecular and
ionic state. These systems are constantly maintained and monitored by
trained personnel using sophisticated equipment.
lacks minerals and oxygen, hence the "flat", "stale"
taste when used for drinking.
In all cases, a Doulton ceramic pre-filter will prevent membrane bacterial
fouling. RO plants producing potable water often use Doulton ceramics
as a final polish filters (physical barrier).
Distillation or demineralization is usually an effective method of
preparing safe drinking water. However, carry-over's of volatile organic compounds (herbicides and/or pesticides) may be an
issue since they may be evaporated and re-condensed with the water.
Like RO, distilled water is very acidic and should be stored in glass container in order to prevent leaching (recontamination).
Since is virtually dematerialized it is often called "starving", "thirsty" or "hungry" water.
Like RO, distilled water lacks minerals and oxygen, hence
the "flat", "stale" taste when used for drinking.
Distilled water is mainly used for industrial processes such as electronic
circuit boards etching and rinsing, photographic's and other applications.
In most cases, pre-filtration, including a ceramic filter element, will improve the effectiveness of a distillation system
by improving the quality of supply water.
Ultraviolet Radiation UV-FAQ
Ultraviolet systems (UV) expose supply water to intense ultraviolet
radiation, which kill pathogenic bacteria (cholera, typhoid, salmonella,
dysenteriae, etc.), virus however is not effective against cysts.
Since UV is not a physical filter, suspended particles (or turbidity)
in the water could “shade” bacteria from the direct rays from the UV source “live” bacteria and virus could pass through the system. For this reason
a good UV systems have ceramic cartridge as a pre and final filter. The following factors can reduce the UV performance:
- Iron and hardness, which build up on the quartz sleeve is a process industry known as "fouling".
- Iron, decayed organic matters, tannins and any UV energy absorptive material commonly found in tap water.
If you own a UV without Doulton ceramic pre-filter and rely on it for
microbiological protection make sure to clean the quartz sleeve often
and chenge the UV bulb once a year.
UV, by itself, does not remove any particulate matter or turbidity. It
does not remove volatile organic compounds such as pesticides or insecticides.
Purchase, installation, operating and maintenance costs should be considered
before selecting UV as a drinking water treatment system.
UV manufacturers performance claim is based on 1 or less than 1
NTU* turbid water.
* Turbidity refers to the concentration
of undissolved, suspended particles present in a liquid measured in
Nephelometric Turbidity Units (NTU). It is important to note that turbidity
is a measure of sample clarity and not colour. Water with cloudy or opaque appearance
will have high turbidity, while water that is clear or translucent will have
low turbidity. High turbidity value is caused by particles such as silt, clay,
microorganisms, and organic matter. By definition, turbidity is not a direct
measure of these particles but rather a measure of how these particles scatter
Turbidity is a very complex analytical measurement which can
be affected by many factors. Some are inherent in the instrument’s
design such as angle of detection, light beam aperture, incident beam
wavelength and colour sensitivity of the photocell. However, there are
other factors such as stray light, air bubbles and care of vial, which
can be prevented through proper care of equipment and accessories.
Most popular Ion exchange (IEX) media in POU for heavy metals reduction
is ATS or ATC media, zeolite etc. Various IEX resins are often used
for industrial processes for specific water use. Ion exchange theory
in layman language is simply gaining and loosing atoms (swapping atoms).
In drinking water for example soluble lead is a positive ion whilst
chlorine is a negative ion (cat ions+, anions-). Most common ion exchange
in rural area (well water) is "Softener".
An other popular often called "emerging technology" or "redox technology"
etc. is IEX media used in POU is KDF 55 (copper zinc
alloy in granule form) for it's high chlorine reduction.
By simply swapping atoms this metal alloy turns chlorine into harmless
Many POU "makers" using this alloy claim soluble lead reduction, bacteriostatic proprieties,
some go as far as cysts and bacteria removal and a host of other "miracles".
We simply don't know what does it do with the lead, does it convert it
to a particulate lead or what pH operating water conditions must be used? Under what condition is bacteriostatic?.
If you plan on buying a POU using KDF media, do your investigating as
to performance claims. KDF 55 is widely use for shower and garden filters which are impressively compact and
There is a range of water purification products on the market and there is Doulton.
Effective and cost efficient drinking water treatment technology.
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