Subject: home water purification systems: a guide to making the right choice, part 2

From: [email-masked] (Ian Hewitt)
Date: Mon, 30 Jan 1995 21:26:59 -0800

(please see part 1 of this guide first)

Reverse Osmosis

   Reverse osmosis, or RO, is another separation process that makes use of
a semi-permeable membrane.  This membrane lets particles of a certain size
or smaller through and keeps back larger particles.
   Like distillation, some contaminants can make it through the membrane
just like water molecules, so a GAC filter is added at the end of the
process to capture these materials.  RO systems also waste three to 10
gallons of water for every gallon produced.
   Also, like distillation, RO water is essentially mineral-free which is
not healthy to drink as a lifetime beverage.  Mineral supplements are
always recommended to take if drinking RO water (as well as distilled
water).  These supplements counterbalance the leaching effect of drinking
mineral-free, aggressive water.
   However, unlike distillation, RO units leave the water well-oxygenated
so that the water taste is much closer to that of "spring water."  The
distilled water always tastes flat and "lifeless."  In cases of extreme
mineralization or high nitrate levels in the water (agricultural areas),
RO units are for the most part the systems of choice.

KDF Resin

   KDF resin is a limited technology that is mainly used for chlorine
removal.  A large amount of the KDF and a long contact time with the water
is needed to do the job.  Therefore,  this resin is best used in large
commercial applications such as boiler systems although it is also used
effectively in some showerhead filters.
   Typically, KDF filters use zinc and copper to create electrolysis that
helps keep bacterial growth down inside the filter.  However, the systems
using KDF may have problems with that zinc and copper leaching into the
water they dispense.
   KDF filters also tend to clog quickly (around six months in some cases)
and this clogging action is dependent on specific water chemistry like pH
and temperature.  Companies using KDF recommend to backwash the filters
(use hot water to dislodge trapped contaminants) but this method wastes
many gallons of hot water, and has no way to prevent dislodged pollution
>from  continuing out with the supposedly purified water.

Ultraviolet Light
   
   Ultraviolet light systems make use of the ability of this portion of
the light spectrum to kill bacteria.  Such systems are only effective on
bacteria and some algae and protozoa, so they are normally combined with
carbon technology to give more complete purification.
   Other drawbacks are:

   --Incomplete purification:  Particles in the water like dirt, leaves,
etc. can prevent the disinfection process from hitting every bacterium,
etc.; some can slip through in cases of heavy silt and sediment levels

   --No residual disinfection down the line:  The process is only good at
the spot where the light is located;  any contamination down the pipeline
is picked up as the water continues down

   --Limited application:  UV light is good only for bacteria.  It does
nothing about giardia, cryptosporidia, chemicals, lead or asbestos.

   --Expensive to purchase and maintain

Ozonation

   Ozone units super-oxygenate water which kills bacteria with adequate
contact time.  Again, this is a process that only addresses bacterial
contamination and so is necessarily combined with carbon filtration to be
most effective.
   Other drawbacks are:

   --Expensive to purchase and maintain

   --Create by-products in the treated water:  Ozonated water can contain
high amounts of toxic contaminants such as formaldehyde and different
ketones.  Some of the created by-products also allow for increased
bacterial growth in the pipes down the line which contributes to
re-infection of the water.

Bottled Water

   Bottled water enjoys a booming business lately due to all of the water
problems covered before.  People drink it because of the improved taste,
and that allows them to drink more water.  What the public doesn't realize
is that the standards for that bottled water are no higher than those for
the tap water in their kitchen.  Bottled water companies are allowed to
sell water with a minimum level of contamination (bacteria, algae, dirt,
lead, etc.).  When the water tastes better, the public perceives it as
purer.
   Here is the scoop on bottled water:

   --Expensive:  The California Assembly Office of Research did a study on
bottled water in 1985 that showed consumers paying up to one thousand
times the cost of tap water for bottled water.

   --Inconvenient:  People who use bottled water regularly tend to have
lots of bottles around underfoot -- empty containers or new jugs waiting
to be used.  These people usually hoard the "clean" water for special
purposes, i.e. coffee, beverages, rather than use it freely whenever
needed.  There is always the problem of having too many bottles on hand
because they are not used fast enough,  or not enough bottles because the
water is being consumed more quickly.
   --No laws requiring it to be purer than tap water:   In 1991, the U.S.
House Energy and Commerce Commission did a study on bottled water with the
following findings:
   
      --25% of "gourmet" waters (i.e. Evian, Perrier, et al)
draw             from the same sources as cities!!
      --31% exceed tap water limits for microbiological             
contaminants!
      --25% could not document their water sources!
      --Any bottled water sold strictly within state borders         is
not subject to regulation by the Food and Drug        Administration!

   The University of Delaware found that of the 37 popular mineral waters,
at least 24 were out of line with at least one of the 31 standards set for
drinking water!
   The California Assembly Office of Research study (1985) also did random
samplings of bottled waters sold in California (name brands such as
Alhambra, Black Mountain, Sparkletts, etc.) and found numerous reported
contamination problems, such as finding various chemicals, insects,
algaes, bacteria, fingernails and even chewing gum! 
   Because of the nature of the bottling and handling process, it is
difficult to avoid casual contamination from different points in the
process.  Air that bubbles up into home drinking water dispensers is laden
with bacteria and dust that contaminates the water each time.  Bottled
water companies recommend keeping the water out of direct sunlight and
even supply covers for the bottles because the algae, etc. that was not
filtered out completely will start to grow in the bottle with warmth and
light (remember the greenish scum?)!

Solid Carbon Block Filters

   This technology has combined the incredible adsorption capability of
carbon discussed previously with the ability of a solid brick of material
to selectively strain out particles from water forced through it.  The
density of the brick determines how finely the water is cleaned.
   The better brands of this type of filter have a three part filter and
are designed to prevent any possibility of "bypass" due to high pressure
failure.
   The following list of features are what combine to create the type of
filter that will remove the widest range of possible contaminants in the
drinking water:

   --Mechanical straining:  the block of carbon mechanically strains out
dirt, sediment, rust, algae, bacteria, microscopic worms, cryptosporidia
and asbestos.  This is all accomplished by water pressure so no
electricity is required -- such a filter even works on a simple hand pump
in emergencies!

   --Chemical bonding:  As explained earlier, activated carbon bonds to
thousands of chemicals.  In fact, carbon will bond to most chemicals known
to man!  When water is forced through the solid carbon block, it is forced
to slow down and increase the contact time with the carbon, allowing the
carbon bonding to take place to remove the chemical pollutants like
toxics, pesticides, THM's, chlorine, bad tastes, odors, etc.
   Health-providing trace minerals like dissolved calcium and magnesium do
not bond to carbon and are allowed to pass through, thereby retaining the
health quality and good taste of the water.
   Heavy metals like lead do not bond to the carbon, but are strained out
by the pore size of the block -- basically like trying to fit a basketball
down a hole designed for a ping pong ball!!
   --Prevention of bacterial growth:  Bacteria are strained out and remain
on the outside of the carbon block.  Therefore, because of the density and
lack of oxygen and space inside the block, bacteria cannot breed in the
medium and come out in the finished water.

   --Convenient:  This type of system provides purified water on demand so
there is no storage, nor running out at inconvenient times, no ordering
bottles or picking bottles up from the store.

   --Inexpensive:  This type of filter is a replaceable, self-clogging
cartridge that lasts eight to 12 months (dependent on amount of sediment
and dirt).  The cartridge is designed to be replaced in minutes at home by
the homeowner, just like screwing in a new light bulb.
   The cost of the units are relatively inexpensive -- over a ten-year
period, the cost of the unit plus maintenance works out to a mere sixty
bucks a year!!  The cost of the water itself is from four to 8 cents per
gallon.
   The units themselves are generally very easy to install and are
designed to be a 45 minute installation for the handy homeowner or
plumber.  They can also be connected with refrigerators that have
automatic icemakers and water dispensers so that all the water that a
household consumes is purified!
   The only drawback to solid carbon block system is they will not remove
nitrates or sulfides (byproducts of agricultural fertilization) and in
these cases are available with RO technology to take care of the problem. 
Nitrates and sulfides are found in relatively few areas however, so most
consumers do not need to worry about them.

Consumer Protection

   Today, there are over 517 different brands of filters on the market and
a lot of confusion in the consumer's mind.  The industry has largely been
self-regulated with bodies such as the Water Quality Association being
looked to for recognition and approval.  Since most of WQA's members are
in the water conditioning and softening end of the market, there has not
been consumer ratings and protection for drinking water systems until just
recently.
   In 1991, the National Sanitation Foundation was accredited by the
American National Standards Institute (ANSI) and RVC, ANSI's European
equivalent.  The NSF is an independent, not-for-profit third-party testing
body that is responsible to the consumer user sector, the regulatory
(governmental) sector and to the manufacturer sector.
   NSF tests any equipment used in food preparation and storage, and that
includes drinking water systems.  They test under Materials Guidelines,
which determine that all the product components (screws, neoprene seals,
tubing, etc.) are safe and not leaching off trace toxins.  They also test
under the Structural Guidelines, which make sure that units will not
explode, crack, disintegrate, etc.
   NSF is now recognized as the drinking water system industry standard
nationwide.  In fact, most states are going to NSF ratings plus their own
state testing which determine what individual manufacturers can claim for
their filters sold within the state.
   California is one of the toughest states to sell in because many
filters do not qualify to sell in the state, based on outrageous
performance claims that are unverifiable.
   Most reputable companies invest in the expense of getting these ratings
(NSF tests can cost $50,000 per test!!) because they recognize the
credibility granted them if their filter measures up.  Therefore, they
strive for as much documentation as possible.
   NSF has two main standards for water filtration devices:

   --Standard 42:  Aesthetic effects
   This rating covers taste, odor and chlorine removal and further divides
the category by percent removal, i.e.
      --Class V:     25% - 49% Chlorine removal
      --Class I:     75% - 100% Chlorine removal

   --Standard 53:  Health Effects
   
      This category covers most every other pollutant, with many of them,
like lead and asbestos, being extremely hard to remove due to size or
chemical structure.  The substances rated for are tested for individually
with each test a separate expense:

      --Chemicals (VOC's, THM's)
      --Pesticides
      --Herbicides
      --Cysts (GIardia, Cryptosporidia)
      --Turbidity
      --Lead
      --Asbestos
      --Radon

   The method in which the filters are tested is to test for 100% removal
of a substance (such as lead, for instance) for twice the rated filter
capacity.  In other words, if a cartridge is rated for 500 gallons by NSF,
that means that it removed lead for one thousand gallons at 100% removal
level.  In this manner, consumers are generously protected for almost any
water situation, by overtesting the unit and conservatively rating the
expected performance.
   Many consumers look to Consumer Reports for trusted performance ratings
on different products.  In the field of water filtration, CR is not nearly
as rigorous in its testing as NSF, either in its methodology or the range
of contaminants tested for.
   In the past ten years, the CR labs have only done lead and chlorine
comparisons on a relatively few filters so their findings are far from
comprehensive.
   NSF is a much more complete source for comparison and because of this,
as of October 1992, all filters sold within the state of California, and
others as well, must state the filter's NSF rating on the unit, the
packaging and all literature related to the filter.  Any violators of this
regulation are prevented from selling their equipment in the state.

Hidden Cost of Filter Maintenance

   There are three other factors to consider in the purchase of a drinking
water system that can be almost as important as the unit performance
itself:

      --Filter replacement costs:  What is it going to take to maintain
the filter over a lifetime of use?  Some filter replacement cartridges run
as high as $80 to $150 per year!!  If possible, it is best to buy
equipment and cartridges directly from the manufacturer because that
insures the lowest possible price.

      --System warranty:  How long is the unit guaranteed to last?  Some
cheaper units have only one year limited warranty, or have a three year
warranty and are designed to be thrown away in three years.  Most of the
units are prorated, meaning that only a partial refund will be given in
the case of failure.  There are only a few units that give a warranty over
five years long.  In general, the longer the available warranty, the
better because this is a direct indication of the manufacturer's
committment to the product and to customer service.
      --Company longevity:  How long has the company been in business and
what are their prospects for staying in business?  In other words, will
the company still be around in 5, 10, 25 years or longer?  The importance
of longevity is availability of filter replacement cartridges and
replacement parts as needed.  Most filter cartridges are not
interchangeable and many consumers have been burned after buying a filter
that three years later was out of business!  The best advice is to stick
with recognized industry leaders that have been in the water filtration
business for at least 15 years or longer.

Conclusion

   By the end of this guide, any consumer should be able to wade through
the hundreds of choices and choose a filter that will fit most any
drinking water need.
   For further information, or for any questions on the information
contained in this guide, please call NSF International at (313) 769-8010
[FAX: (313) 769-0109], Pure Water Network at 
(800) 869-6691, or send your e-mail to [email-masked].

[Dr. Denise Downey is a biologist who has been actively involved
nationwide in the water purification industry for over ten years.]
c 1994