The Contaminant Removal Table itself begins just below
the Key: The contaminants are listed in columns across the top of the chart.
Also indicated are
the type of contaminant; biological, inorganic, or organic.
The treatment methods are listed in rows down the left side.
At the intersection of a contaminant column and a treatment method row will be
notation about the removal effectiveness of the treatment method on the
Important information about some topics are indicated by numbers throughout
linked to notes following the chart.
Some of the contaminants or treatment methods have links to outside sources
Other contaminants that would not fit across the table
(turbidity, hydrogen sulfide, odor &
taste, acidity & alkalinity, and radon
& radium) are discussed after the main table.
This is by no means a complete list of all possible contaminants - there
would be many
thousands. I have included the more important and/or common
contaminants in this list.
It is important to actually know what contaminants are present in your
water (or might be
introduced accidentally) before investing in a treatment
method. If you are on municipal
water, obtain and read your annual water
quality report. If you have a well or use surface
water, try to determine
which contaminants are most liable to be present (try the local
EPA office, local
health department, neighbors, local water companies, etc.) and have it
Nuisance contaminant, may cause problems with the plumbing,
Beneficial (in the case of chlorine, the
benefit is not because it is an essential mineral, like calcium or copper,
rather chlorination has played a critical role in protecting the world's
drinking water supply from waterborne infectious diseases for nearly 100
Contaminant is beneficial at low doses but can cause health
problems at higher levels. Fluoride is a classic example. It
provides protection from cavities at levels of about 1 part per million (ppm). At 1.5-2
ppm it can cause staining of the teeth, and at 4 ppm or
above it may cause bone problems.
Removal effectiveness of the treatment method on a
Disinfection - Effectiveness depends on the proper
dose and contact time of the disinfection agent.
Mostly Removed - If the device is working properly
Some Removal - may depend on what chemical form the
contaminant is in at the time of treatment, iron and arsenic are examples.
Depends on the manufacturer, particularly for
activated carbon filters where special manufacturing processes can
increase the level of specific contaminants removed. Ask
manufacturer for independent certification of removal (and the percent removal). A claim
of "removes or reduces lead" can be true if the unit removes 10%
Boiling concentrates those contaminants not removed or
Some disinfection methods can add contaminants to the
ongoing cost of treatment per gallon 2 (not
including the initial cost of the system)
Bottled water is unique among
the other treatment methods listed, because the consumer does not have any
control over the purification process. All harmful
contaminants should be removed by the water bottler. Bottled water,
however, does not have to meet any higher levels of purity or safety than tap
water. To insure the quality of your bottled water, make certain
that you purchase water certified by NSF or that the manufacturer is a member
of the International Bottled Water Association (IBWA)
pH correction using either a tank-type neutralizing filter with
processed calcium or magnesia in combination with calcium as the media, a
chemical feed pump to inject a neutralizing solution (soda ash, potassium
or sodium hydroxide) into the water, or a pressure filter tank filled with
pH higher than 7
pH correction using either a neutralizing filter or chemical-feed pump
to lower the pH
Aeration is very effective for removing radon from drinking water.
Radon can also be removed with an Activated Carbon filter. Radium
can be removed with RO, cation exchange, and distillation.
Notes: 1 - Iron is a common nuisance contaminant mostly for people with their
own wells, water treatment companies tend to remove it fairly effectively. It can
be found in a number of forms in drinking water, soluble, insoluble, organic,
and as a contributor to an iron bacteria problem. Go to the
Iron and Manganese Removal article for more information.
Treatment methods for iron include:
Iron filters - Iron filters are only useful for removing soluble
iron and manganese; precipitated iron particles will quickly plug them. They
appear similar to water softeners but contain a bed of natural or synthetic
manganese green sand. Manganese dioxide oxidizes iron and manganese and the
oxidized particles are then filtered out in the lower part of the bed. The
filter bed must be backwashed frequently to remove the accumulation of iron
particles. For backwashing, a flow rate more than double the normal service flow
rate is usually required. The exhausted manganese must be recharged by adding
potassium permanganate. Since the slime produced by iron bacteria will
clog the filter, the iron bacteria must be controlled before using an iron
filter. Back to chart.
Standard water softeners can remove small amounts of dissolved iron
(5 to 10 ppm). With special resins and regeneration processes, up to 5
mg/l of soluble iron can be removed. Iron bacteria must be controlled before
passing through the resins, since the slime produced by iron bacteria will clog
the resin and reduce its effectiveness. Oxidized iron (precipitated rusty
sediment) must also be removed before treating with an ion exchange resin to
prevent the resin from becoming clogged.
Polyphosphate feeders - These units can handle up to 3 mg/l of iron
in solution. They contain a phosphate compound which coats the soluble iron and
prevents its oxidation when the water is exposed to air. The compound is not
effective against iron that has already oxidized. When some waters are
heated, the raised temperature will reduce the effectiveness of the
polyphosphate so that oxidized iron will accumulate in the water heater. The
heated water will be rusty and unsatisfactory for many home uses. Polyphosphate
is most effective in cold water.
Chlorination and filter. Chlorination followed by filtration
through a sand filter can remove any quantity of iron in any form. The chlorine
oxidizes and precipitates the iron and the filter removes the particles. Carbon
filtration may be required to remove excess chlorine.
Ozone will also oxidize the iron and manganese causing them to
precipitate so they can be filtered. Back to chart.
2 - The costs are very approximate because of a wide variety of
factors. Listed costs also do not include the initial expense of the
treatment equipment. The ongoing costs listed are mostly useful for POU and bottled water users
and are meant to give you a feel for the relative expenses you would incur over
a period of time. For example, bottled water at about $0.25 to more than
$1.00 per gallon (much more if you purchase "designer" water) would
cost at least 3 to more than 10 times as much as an equivalent amount of
purified water filtered through a carbon block filter at about $0.05 to $0.10
per gallon. If economics are important to you and you are using more than
a couple of gallons of treated water a week, this information might be
useful. Back to chart.
3 - I am afraid I do not know anything about magnetic or electromagnetic
conditioning of water. I do not have a hard water problem and thus have
not had a motivation to try the technique. I have also not been able to
get any unbiased information on the effectiveness of this treatment. I
listed it here because it is a widely advertised alternative to traditional
water softening which is not particularly environmental (or health) friendly,
and, if it actually works, would be a valuable addition to hard water treatment
methods. If anyone has first hand experience with these devices or knows
of a link to an independent review article, please let me know, and I will
report anything I discover. Back to chart.
4 - Reverse Osmosis, Ceramic Filters, and
Carbon Block Filters can have pore sizes of 0.5 micron or less (RO membranes are
far smaller) which can remove many harmful bacteria very effectively. It
is best, however, not to depend on these treatments for your primary, ongoing
disinfection method for water that is known (or suspected) to have harmful
bacterial contamination. A damaged filter element could allow enough
bacteria into the "filtered water" stream to cause illness - and there
would be no way to detect the problem without constant testing. They are
definitely reliable enough, however, to be used as a backup system with normally
safe domestic water (in case of accidental contamination) or for water treatment
in case of an emergency where normal water distribution is disrupted and the
available water may be contaminated.. (Granular Activated Carbon) filters (because of the inconsistent pore size discussed below)
will NOT safely remove bacteria from drinking water. You will see some of
these systems marketed with embedded silver - this is to help prevent trapped
bacteria from growing within the filter media. I have not seen any independent tests on the ability of KDF filters to
reduce bacterial contamination in running water. From my reading, it
appears that the KDF media prevents trapped bacteria from growing or
multiplying. Back to chart.
5 - Activated carbon, whether as fairly large granules, in granulated
activated carbon (GAC) filters, or compressed into solid carbon blocks filters,
is very effective at removing a wide variety of organic compounds. I
placed a S 5 for whole house and point of use GAC filters
because 1) water moves through a whole house filter (unless it is
enormous) too fast for complete removal of anything except particles smaller
than the largest pore size (usually 10-20 microns), and 2) GAC filters, because they contain
loose carbon particles and are prone to channeling, where the flowing water creates
relatively large channels through the filter medium. Water moving through
these channels does not have much contact with the activated carbon, and thus,
filtration of the channeled water is minimal. However, if organic
chemicals are a significant contaminant in the water entering your home, a whole
house, GAC filter will help reduce the level of these
contaminants. This is important, because many organics can vaporize in a
shower, for instance, and be inhaled. If you choose a whole house carbon
filter, be aware of their limitations though, and seriously consider a Point of Use SBAC
filtration system to treat your drinking and cooking water. Also, if you have a
yard or garden that is watered by your household water, and if it is at all possible,
consider splitting your water line so unfiltered water is sent to your outside
taps - otherwise you must change the filter much more often. Back to chart.
6 - Iron bacteria are mostly a problem for people using wells water with
high iron or manganese concentrations. The bacteria themselves do not
necessarily clog filters, but the brown slime they produce may. None of the POU treatment devices would be effective for the treatment
of iron bacteria. If this is a problem, one of the methods described below
should be used to remove the bacteria and "slime" before the water
reaches a POU device. The Penn State Extension has a site, The Facts on Iron Bacteria, that provides additional information about
preventing and treating the problem.
7 - All ion exchange resins work by exchanging the contaminant you
wish to remove with one that is less harmful or annoying. Water softeners
usually exchange salt
for the calcium and magnesium in the water. Salt concentrations are
usually low and not a health concern, unless you are on a restricted sodium
diet. The residual salt or other exchange chemicals eventually get dumped
into the septic system or sewer, however. There are several
types of ion exchange resins available to treat different water
contaminants, cation (water softeners - removes positively charged ions), anion
(removes negatively charged ions like nitrates and sulfates), and mixed bed
resins containing both cation and anion resins. Back to chart.
8 - A RO systems should come with a pre-filter (a sediment filter and
perhaps a chlorine filter) to remove contaminants that would damage the RO
membranes. A Reverse Osmosis filtration system should also come with a
high quality Activated Carbon filter to remove organic and some inorganic
compounds that are not removed by the RO membranes. Besides RO there
are other types of
membrane filtration (Microfiltration, Ultrafiltration & Nanofiltration),
where water is forced through different size semi-permeable membranes. Read note 4 for
information about microbial filtration. Back to chart.
9 - Water usually contains dissolved gases and may contain other
substances, like some of the organic chemicals, that can be volatilized at
temperatures below the boiling point. When the boiling point of volatile
chemicals is near water, it is difficult to separate these materials from water
using distillation. In addition, the separation of steam from the liquid that
contains dissolved solids is not absolute. Minute amounts of the dissolved
materials will be carried along with the steam. Distillation normally removes
over 99.9 percent of many dissolved materials. A gas vent, fractional
column, or carbon
filter should be included with any distillation system you purchase to remove
the volatile contaminants. Back to chart.
10 - Ultraviolet (UV) light is capable only of
disinfecting water, no other contaminants are removed. Different pathogens
require different doses for treatment (cysts require a higher dose than most
bacteria, for example), so make certain any UV system you consider is capable of
killing the specific microbe(s) you are concerned about. In order for UV disinfection to be completely effective, the water coming
into the UV chamber must be extremely clean. Any particulate material may
"shadow" the pathogens and allow live microbes to exit the UV system.
Back to chart.
11 - Solid Block Activated Carbon Filters are not usually described
separately from loose carbon (GAC) filters.
This article does a good job starting on page 24. The list of water contaminants and available
treatment technologies can be rather overwhelming. After
all is said and done, though, a high quality, Solid Block Activated Carbon filter
(SBAC) (designed to remove the most common drinking water contaminants) would be my recommendation for
probably 80%+ of people concerned about their drinking water quality -
the other 20%,or so may have more serious contaminant problems, and will need to
explore more complex (and expensive) treatment solutions specific to their
After considerable research, a Solid Block Activated Carbon filter
was the solution I selected for my home.
My strategy was to figure out what contaminants were actually in my water
(or might be released into my water due to an accident) and then choose the
treatment method: 1) that would reliably
remove those contaminants, 2) had the lowest
operating and maintenance costs over the 30 - 40 years I planned to use it, and
3) be the easiest to use and required the least maintenance.
Denver municipal water, like water from most medium to large public water
sources is very good quality overall, but it contains chlorine and disinfection byproducts
(DBPs). Even though the DBPs were present at
levels below the EPA maximum contaminant levels, they were still of
concern because of the health risks of long term exposure (discussed elsewhere on
my site). Although I did not test for lead, I strongly suspected it
was present in our 55 year old home, because (as discussed elsewhere), lead is quite prevalent in both
new and older homes. Contaminants I was concerned might be released into
the water because of an accident included E. coli, giardia or cryptosporidia
cysts, and possibly some organic contaminants like MTBE. Arsenic,
and other harmful inorganics, like nitrates, cadmium, etc. were very
unlikely to ever be our municipal water in significant or harmful quantities.
Other Organic contaminants like pesticides and solvents were also
unlikely to ever be present, although a SBAC filter will remove wide variety of
There were four available technologies that would fairly simply remove all
the contaminants that I wanted to protect my family and me against; Bottled
Water from a certified company, Distillation, Reverse Osmosis, and Solid Block
Activated Carbon filters. Of these four treatment methods, SBAC
filtration systems were easily the simplest to use and maintain (normally
one filter change every year or so). SBAC filtration also had the lowest
ongoing costs at about $1.00 per week for up to about 14 gallons of purified
water per week ($2.00 a week if you filter 14-28 gallons/week, and so on).
Most people using
regulated municipal water will have home water characteristics similar to mine -
fairly clean, biologically safe water with known contaminant levels, and a low
risk of accidental contamination. A SBAC filtration
system would be an ideal choice if this describes your water. Even if you
soften your water, a SBAC filtration system would be a good addition to your
treatment plan, because softening, by itself, does not remove any contaminants
harmful to health that might be present. People using well water with the
same characteristics as described above would also benefit from the protection
of a SBAC filtration system. Back to chart.
Final thoughts and disclaimer:
In the table and notes above I have attempted to summarize the most
common treatments for the most prevalent and important drinking water
contaminants you are liable to encounter. The notations indicating which treatment method removes
which contaminant are as accurate as I could make them after reviewing many
sources, but you will need to carefully double-check any decision you make
regarding a treatment method with the manufacturer from which you plan to purchase
the treatment unit to make certain that it is certified do what you expect it to do. Three reasons for
double checking: 1) an error may have been made by me or by one of my
sources. 2) Technology changes rapidly, so there may be newer methods on
the market than I am aware of, and 3) all treatment "units" are not
created equal - for example, there are several thousand filtration systems on
the market. Some reliably remove a wide range of inorganic and inorganic
contaminants while others remove only a couple. Also, filters from some
uncertified companies may have
chronic manufacturing defects that render them useless.
protection for purchasing a filtration system or bottled water is to make
certain it is certified by a third party to perform as advertised. NSF International is a group that certifies water treatment systems, distillation
units, bottled water, water softeners, and a number of other food preparation
systems. NSF certification means that not only do the products perform
as tested, the product advertisements are also evaluated for accuracy and
truthfulness. Products are tested on an ongoing basis to make certain
that companies continue to produce products that perform as advertised.
The bottled water industry regulates itself through
the International Bottled Water Association
The IBWA sets manufacturing requirements, which help to ensure that bottlers
meet FDA health standards.
Any person who requires water of a specific
microbiological purity should follow the advice of their doctor or local health
officials regarding the use and consumption of tap water treated by ANY
Other considerations for purchasing a water treatment system (or bottled
-Is the treatment appropriate for the problem? For example, with hard water the
equipment must remove calcium.
-Is the treatment cost effective? If you plan on using it more than a
couple of years, the ongoing and maintenance costs can far outweigh the initial
cost of the filtration system. Bottled water, for instance, has continuing
ongoing costs while a filter might have a high initial cost but cost very little
to maintain over the next 40 years or so.
-Is the equipment guaranteed?
-How long has the vendor been in business? Do they have a good reputation?