United States
Environmental Protection Office of Water EPA 810/F 93 OQ2
Agency (WH-550) July 1993
&EPA EMERGENCY DISINFECTION OF
DRINKING WATER
There are two general methods by which small quantities of water can
be effectively disinfected. One method is by boiling. It is the most positive
method by which water can be made bacterially safe to drink. Another
method is chemical treatment. If applied with care, certain chemicals will
make most waters free of harmful or pathogenic organisms.
When the home water supply system is interrupted by natural or other
forms of disaster, limited amounts of water may be obtained by draining the
hot water tank or melting ice cubes. In most cases, ground water is
generally the preferred source of drinking water. If it is not available and
surface water must be used, avoid sources containing floating material or
water with a dark color or an odor.
When emergency disinfection is necessary, the physical condition of
the water must be considered. The degree of disinfection will be reduced in
water that is clouded. Murky or colored water should be filtered through
clean cloths or allowed to settle, and the clean water drawn off before
disinfection. Water prepared for disinfection should be stored only in clean,
tightly covered, containers not subject to corrosion.
METHODS OF EMERGENCY DISINFECTION
BOILING. Vigorous boiling for three minutes will kill any disease-
causing microorganisms present in water. The flat taste of
boiled water can be improved by pouring it back and forth
from one container into another (called aeration), by
allowing it to stand for a few hours, or by adding a small
pinch of salt for each quart of water boiled.
CHEMICAL When boiling is not practical, chemical disinfection should
TREATMENT be used. The two chemicals commonly used are chlorine
and iodine.
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CHLORINE CHLORINE BLEACH. Common household bleach contains
a chlorine compound that will disinfect water. The
procedure to be followed is usually written on the label.
When the necessary procedure is not given, one should
find the percentage of available chlorine on the label and
use the information in the following tabulation as a guide.
Drops per
Available Chlorine1 quart of
clear water2
1% To""
__ _
__ .
1 If strength is unknown, add 10 drops per quart of water.
2 Double amount for cloudy or colored water.
The treated water should be mixed thoroughly and allowed
to stand for 30 minutes. The water should have a slight
chlorine odor; if not, repeat the dosage and allow the
water to stand for an additional 15 minutes. If the treated
water has too strong a chlorine taste, it can be made more
pleasing by allowing the water to stand exposed to the air
for a few hours or by pouring it from one clean container
to another several times.
GRANULAR CALCIUM HYPOCHLORITE. Add and dissolve
one heaping teaspoon of high-test granular calcium
hypochlorite (approximately 1/4 ounce) for each 2 gallons
of water. This mixture will produce a stock chlorine
solution of approximately 500 mg/L, since the calcium
hypochlorite has an available chlorine equal to 70 percent
of its weight. To disinfect water, add the chlorine solution
in the ratio of one part of chlorine solution to each 100
parts of water to be treated. This is roughly equal to
adding 1 pint (16 oz.) of stock chlorine solution to each
12.5 gallons of water to be disinfected. To remove any
objectionable chlorine odor, aerate the water as described
above.
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CHLORINE TABLETS. Chlorine tables containing the
necessary dosage for drinking water disinfection can be
purchased in a commercially prepared form. These tablets
are .variable from drug and sporting goods stores and
should be used as stated in the instructions. When
instructions are not available, use one tablet for each quart
of water to be purified. q
IOD,NE ™CTU"E OF IOD'"e- Common household iodine from
the med.c.ne chest or first aid kit may be used to disinfect
water. Add five drops of 2 percent United States
Pharmacopeia (U.S.P.) tincture of iodine to each quart of
clear water. For cloudy water add ten drops and let the
solution stand for a least 30 minutes.
IODINE TABLETS. Commercially prepared iodine tablets
contaming the necessary dosage for drinking water
disinfection can be purchased at drug and sporting goods
stores. They should be used as stated. When instructions
are not available, use one tablet for each quart of water to
be purified.
^!£LE?n ™ BE USED FOR DRMKING, COOKING, MAKING ANY
PREPARED DRINK, OR BRUSHING THE TEETH SHOULD BE
PROPERL Y DISINFECTED ^UULD BE
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