EPA'S DISINFECTION POLICY
While protecting public health is of primary concern,
the need to protect aquatic ecology must be considered
along with the need for disease-free water. To achieve this
goal, discharges of chlorination residuals and by-products
should be reduced where possible, as long as public
health is not compromised. The preamble to EPA's 1976
Secondary Treatment Regulation and EPA's disinfection
'policy (41 Federal Register, pp. 30786-89 July 26,1976),
summarized below, reinforce this view.
The U.S. Environmental Protection Agency (EPA)
believes that although the protection of public
health from disease will remain a major criterion in
making decisions about disinfection requirements,
protection of public health can be maintained with-
out continuous disinfection of all municipal
wastewater discharges. Regulations which require
disinfection where it is not needed unnecessarily
increase toxiciry to human and aquatic environ-
ments. Due to potential problems associated with
the unnecessary use of disinfectants and the vari-
able need for disinfection, the EPA's policy is that
disinfection requirements be set on a case-by-case
basis, consistent with appliciable state water quali-
ty standards for bacterial indicator organisms and
for chlorine. In addition, serious consideration
should be given to the use of dechlorination or al-
ternate disinfection processes in those areas where
organic compounds which can react with chlorine
to form potentially toxic compounds are known to
exist in the wastewater.
EPA ACTIVITIES
EPA is developing additional guidance on ways to
reduce chlorine impacts on aquatic life. This will include
documents which address topics such as:
• Improving chlorination efficiency
• Seasonal disinfection
• Alternate disinfection technologies and
dechlorination
• Procedures for evaluating the impacts of modifying
disinfection requirements on public health and
aquatic life
ADDITIONAL INFORMATION
For more general information, contact:
Office of Municipal Pollution Control
Performance Assurance Branch (WH-595)
U.S. Environmental Protection Agency
Washington, D.C. 20460'
202-382-7356 •
For technical information, contact:
Dr. Albert D. Venosa
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
513-569-7668
The following publications are available through the
National Technical Information Service (703-487-4650)
and the Instruction Resource Center (614-292-6717):
Municipal Wastewater Disinfection State-of-the-Art
Document. (EPA/430/09-91-02) U.S. Environmental
Protection Agency. Office of Municipal Pollution
Control. Washington, D.C.
Municipal Wastewater Disinfection: Protecting Aquatic
Life and Human Health. (EPA/430/09-91 -01) U.S.
Environmental Protection Agency. Office of
Municipal Pollution Control. Washington, D.C.
Proceedings of the Municipal Wastewater Disinfection
Policy Review Task Force. (EPA/430/09-91-03) U.S.
Environmental Protection Agency. Office of
Municipal Pollution Control. Washington, D.C.
Other References:
EPA Design Manual - Municipal Wastewater
Disinfection. (EPA/625/1-86-021) U.S. Environmental
Protection Agency. Office of Research and
Development. Water Engineering Research
Laboratory, Cincinnati, Ohio.
M
United States February 1991
Environmental Protection
Agency
&EPA Municipal 832pgiooi
Wastewater
Disinfection
Protecting Aquatic
Lifeand Human
Healthfrom the
Impacts of
Chlorination
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THE CHLORINATION CHALLENGE:
PROTECTING PUBLIC HEALTH
AND AQUATIC LIFE
Chlorination has long been the primary method of
disinfection for municipal wastewater. Its use provides
substantial public health benefits by reducing discharges
of many waterborne disease-causing organisms
(especially bacteria) to water supplies, recreational
waters, shellfish waters, and other waters that can
potentially transmit disease to humans.
Despite its tremendous benefits, chlorination has a
negative side. A variety of substances have been found
in wastewater effluents as a result of chlorination. Some
are known to be (and others are suspected of being)
harmful to humans and aquatic life when discharged
to the environment.
CHLORINATION RESIDUALS
AND BY-PRODUCTS
The substances produced during wastewater
chlorination can generally be categorized as chlorination
residuals and chlorination by-products.
Chlorination residuals include free chlorine
(hypochlorous acid and hypochlorite ion) and various
forms of combined chlorine, which result from reactions
with ammonia in wastewater. Free chlorine is a highly
effective disinfectant. Combined chlorine is less effective
but its action persists for a longer time. Free chlorine and
combined chlorine together are often referred to as total
residual chlorine (TRC).
Chlorination by-products are the result of chlorine
reacting with organic compounds in wastewater. The
most widely recognized group of these compounds is the
trihalomethanes (THMs). Some THMs (e.g., chloroform)
are possible carcinogens.
IMPACT OF CHLORINE ON AQUATIC LIFE
The harmful effects of chlorination residuals on
aquatic life have been recognized for many years. Even at
the low concentrations produced at wastewater treatment
plants, fish and invertebrate species can suffer short- and
long-term effects, such as:
• Death
• Changes in population diversity and density
• Inhibited growth
• Changes in reproduction and migration
• Avoidance of chlorine plumes by mobile organisms,
which can mean loss of habitat, increased
environmental stress, and depressed activity
Aquatic plants are less susceptible, but are not
immune to the toxic effects of chlorination residuals.
Chlorination by-products may be toxic to aquatic life,
although little information is available about specific
effects.
HOW WIDESPREAD IS THE
PROBLEM OF CHLORINE TOXICITY?
Chlorination is widely practiced because of its low
cost, availability, and bactericidal effectiveness. Because
wastewater chlorination is so prevalent, there is
widespread potential for adverse effects on aquatic life
from discharges of chlorination residuals and by-
products.
In 1986, EPA studied 6300 municipal wastewater
treatment plants that chlorinate and discharge to
freshwater streams. This analysis showed that up to two-
thirds of the plants were likely to discharge wastewater
that exceeded EPA's acute freshwater chlorine criteria. As
a result, some 3500 different water bodies may be at risk.
REMEDIES TO HARMFUL
IMPACTS OF CHLORINATION
Despite their potential severity and extent, the
ecologically harmful impacts of wastewater chlorination
are easy to reduce compared to other forms of toxicity
because the sources are known and readily controlled.
Three strategies can be used to reduce the impacts of
chlorination residuals and by-products on aquatic life:
1) Eliminate or Reduce Some Disinfection Requirements.
One way to reduce discharges of chlorination
residuals and by-products is to eliminate unnecessary or
excessive disinfection practices. It is likely that some
disinfection requirements can be eliminated or reduced
without exceeding acceptable levels of risk to public
health. For example, seasonal disinfection may be
adequate where recreation is unlikely to occur year-
round.
2) Make Operational Improvements.
Improvements in chlorination efficiency can
effectively reduce discharges of chlorination residuals and
by-products at many treatment plants. Chlorination
efficiency can be improved by upgrading treatment
systems to allow for rapid mixing, plug flow contacting,
and automatic residual control.
Changes in the treatment process prior to disinfection
to reduce pathogens and organics can also reduce the
need for chlorination and maximize efficiency. However,
these changes may affect other aspects of plant operation,
such as sludge processing.
3) Change the Disinfection Technology.
A number of alternative disinfection technologies,
such as ultraviolet (UV) radiation and ozonation, can be
used in place of chlorination. These technologies are often
less hazardous to aquatic life than chlorination, and are
becoming more functionally and economically viable.
Dechlorination, the process of removing chlorine
residuals after chlorination, can also be used to reduce
discharges of chlorine residuals, but not by-products. This
technology is economically feasible and can be added to
most wastewater chlorination facilities.
Several natural treatment technologies, such as
lagoons, constructed wetlands, and other land treatment
systems, enhance natural die-off of pathogens. These
technologies have the potential to reduce the need for
chlorination.
EPA CHLORINE CRITERIA
In 1985, the U.S. Environmental Protection Agency
(EPA) published criteria to provide guidance on
maximum levels of TRC that are believed to protect
aquatic life. States can use these criteria when establishing
water quality standards to protect the aquatic
environment. Close to half of the States have adopted
chlorine water quality standards that are based on these
criteria. The recommended criteria are:
Freshwater.
• acute criterion (1-hour average): 19 ug/1 (ppb)
• chronic criterion (4-day average): 11 ug/1 (ppb)
Saltwater
• acute criterion (1-hour average): 13 ug/1 (ppb)
• chronic criterion (4-day average): 7.5 ug/1 (ppb)
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832F91001ES
Attachment for flyer entitled "Municipal Wastewater Disinfection - Protecting Aquatic Life and
Human Health from the Impacts of Chlorination" (February 1991) (assigned EPA # 832-F-91-
001 after the initial printing)
Thank you for ordering the flyer indicated above. We regret the information indicated on the
back of this flyer is incomplete. The explanation indicated below has been prepared in a
chronological order as appears on the back of the document.
(1) "Municipal Wastewater Disinfection State-of-the-Art Document (EPA 430/09-91-002)"
NEVER FINALIZED
(2) "Municipal Wastewater Disinfection: Protecting Aquatic Life and Human Health" (EPA
430/09-91-01) is an incomplete title. The title of this material is as follows: "Municipal
Wastewater Disinfection - Protecting Aquatic Life and Human Health from the Impacts
of Chlorination" (see above) (430/09-91-001) THE # OF THIS MATERIAL WAS
CHANGED TO THE 832# INDICATED ABOVE. (Item in-hand)
(3) "Proceedings of the Municipal Wastewater Disinfection Policy Review Task Force" ( EPA
430/09-91-003) NEVER FINALIZED
(4) "EPA Design Manual - Municipal Wastewater Disinfection" (EPA 625/1-86-021) (1986)
is available from the following address:
ERIC/CSMEE
1929 Kenny Road
Columbus, Ohio 43210-1015
Telephone: 1-800-276-0462
We regret any inconvenience the above-mentioned corrections may have caused but encourage
you to check our website for more information on disinfection. The website is as follows:
www.epa.gov/owni (click on Municipal Technologies and then to Innovative and Alternative)
Again, thank you for your interest in the environment.
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