Chlorination: Part Two, The Removal
by Stephen K. Wiman, PhD of Goodwater Company, Santa Fe, New Mexico
In regulated municipal water systems, the U.S. EPA Surface Water Treatment Rule (2002) requires that a
minimum disinfectant residual of 0.2 milligrams per liter (or parts per million) of free chlorine be present where the
water enters the distribution system and that it be detectable throughout the distribution system. The role of
disinfectants in protecting public water supplies is well documented and undisputed, but the reactions of some
disinfectants with some natural materials in water and with other treatment chemicals, and the subsequent
formation of unwanted by-products, are of concern. Risk to human health is not clearly documented, but
experiments with laboratory animals do raise warning flags and numerous studies suggest the health risks of both
chlorine and chlorine by-products to humans.
Some consumers elect to remove disinfection chemicals and disinfection by-products from tap water. Such
removal does not itself constitute a health hazard, as your household plumbing infrastructure is a closed system
and you will not be compromising disinfection effectiveness. What method you use to eliminate chlorine, should
you choose to do so, depends on what is in your water (check your local Water Quality Report or lab test results
for a well), your contaminant and health concerns, your budget and (sometimes) your space limitations.
Options for point-of-use chlorine removal include carafes and pitchers, faucet-mounted systems, countertop
filters, and undersink filters. These systems should be considered as “chlorine plus” filters, and some systems
are limited to little more than chlorine removal. Shower filters are also available to minimize chlorine inhalation
while bathing and some showerheads also contain contaminant-specific media for reducing metals in the water.
Distillation systems are also very effective in solving most drinking water problems, but because of their high
energy consumption they are not widely popular.
It is imperative to know exactly what the filter system you select will actually remove from your water. NSF/ANSI
standards (National Sanitation Foundation International/American National Standards Institutions) represent the
gold standard for water product certification. See www.nsf.org/Certified/DWTU/ to search by manufacturer,
reduction claim, type of filter and model name or number. Almost all water filtration products have parts and
media certified under NSF/ANSI Standard 61 for Drinking Water System Components – Health Effects. But the
critical standards for contaminant removal are Standard 42 Drinking Water Treatment Units – Aesthetic Effects
and Standard 53 Drinking Water Treatment Units – Health Effects. Standard 58 covers the contaminants of
known health risk. Technically speaking, chlorine is not considered a contaminant by the EPA. See Table 1.
Table 1 NSF Standards
NSF/ANSI Standard Reduction Performance (Performance Data Sheet)
Standard 42 DWTU –
Bacteriostatic effects, chloramine reduction, chlorine
reduction, hydrogen sulfide, nominal particulate reduction,
scale control, taste and odor reduction, zinc reduction.
Standard 53 DWTU –
Cysts, lead, VOCs (Volatile Organic Chemicals), MTBE.
Standard 58 Reverse
Osmosis Drinking Water
Treatment Systems *
Arsenic V, Barium, Cadmium, Chromium III and VI, Cysts,
Fluoride, Nitrate, Nitrite, Radium 226/228, Selenium, and
TDS plus effectively everything under Standard 53
because of GAC filtration to protect the RO membrane.
*NSF does not certify against Uranium reduction,
but post-RO lab testing confirms the reduction of Uranium.
wThe most common method of removing chlorine is by using carbon (often mis-identified as “charcoal”) filtration.
Some carbon filters are predominantly made from coal (the use of “iodine content” is a tip-off). But he most
effective chlorine filters are made of GAC (granulated activated carbon) made from coconut shells, a renewable
resource which some manufactures are now making with “green” technology (capturing the greenhouse gases
from the ovens used to toast the carbon to create its high volume of surface area).
Activated carbon is effective, but it can provide a base for the growth of bacteria, has to be replaced (or wastefully
backwashed) on a regular basis and becomes less effective through time because of channeling. An increasingly
popular method of removing chlorine is by whole-house filtration, both using canister filters and tanks. Both
methods are limited by the type of carbon used. One method uses in-line canisters (typically 4”x20”) containing
carbon block filters which are changed annually. Carbon block filters are created by compressing very finely
pulverized activated carbon in a binding medium and fusing it into a solid block. Carbon block filters can remove
particles down to 0.5 microns and also remove Giardia and Cryptosoridium if present and eliminate the problems
of channeling. These filters are so dense that they minimize the potential for bacterial growth.
Other whole-house, chlorine-removal devices are stand-alone carbon tanks used in complex treatment
sequences, or tanks which may be combined with embedded electromagnetic devices. These latter systems are
frequently backwashed and may waste as much water as a softener. Dealers make claims that such systems
eliminate the need for bottled water (if you have not already eliminated it from your life) but they in no way protect
you from more harmful contaminants which might be of concern to you in both municipal and well water.
Remember that EPA regulations only require public water systems to reduce contaminants, on an annualized
basis, below the MCL (Maximum Contamination Level) and at certain times of the year individual contaminants
may be near or over the MCL. And if you are on a well, you as the owner are responsible for knowing what is in
your water and for electing what (if anything) to remove. Because of the potential for bacterial growth, carbon
filtration is often a poor choice on wells except where chlorine is used for specific oxidation applications (such as
for Iron, Manganese or Arsenic III) and then removed by carbon block filters typically changed on a scheduled
Contaminant Removal by Activated Carbon
Does Not Remove
Chlorine taste and odor, Chloramines,
Mercury, Pesticides, Radon (poses accum.
hazard), THMs, VOCs (Volatile Organic
Arsenic, Chloramines, Chromium,
Cysts, Fluoride, Iron, Nitrate,
AA plus Cysts, Lead and HAAs.
AA. (Must be changed regularly.)
Table 2 is an illustration of what activated carbon filtration does and does not remove. Claims for contaminant
removal beyond chlorine and chlorine by-products are often undocumented and highly exaggerated. Many filters
and whole-house systems are “certified to” but not “certified by” true NSF/ANSI standards. Some manufacturers
present a self-certified, sliding-scale rating of the contaminant-reduction potential of their products. There is no
substitution for independent certification. Caveat emptor.