[at-l] Emergency Disinfection of Drinking Water

[WHHAWKINS@aol.com]

IMO.  All of the Chemical treatment's should only be used for the short term.
Bleach is a poison.

Wildbill


This is from the EPA

Emergency Disinfection of Drinking Water

When the home water supply is interrupted by natural or other forms of 
disaster, you can obtain limited amounts of water by draining your hot 
water tank or melting ice cubes. In most cases, well water is the 
preferred source of drinking water. If it is not available and river or 
lake water must be used, avoid sources containing floating material and 
water with a dark color or an odor. 

When emergency disinfection is necessary, examine the physical condition 
of the water. Disinfectants are less effective in cloudy water. Filter 
murky or colored water through clean cloths or allow it to settle, and 
draw off the clean water for disinfection. Water prepared for 
disinfection should be stored only in clean, tightly covered, 
containers, not subject to corrosion. 

There are two general methods by which small quantities of water can be 
effectively disinfected. One method is 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 water free from harmful or pathogenic organisms. 

METHODS OF EMERGENCY DISINFECTION. 

Boiling: Vigorous boiling for one minute 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 to 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 treatment: When boiling is not practical, chemical disinfection 
should be used. The two chemicals commonly used are chlorine and iodine. 


Chlorine Methods: 

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, find 
the percentage of available chlorine on the label and use the 
information in the following tabulation as a guide.


Available Chlorine..........................Drops per quart of clear water
1%...............................................................10
4-6%..............................................................2
7-10%............................................................1

(If strength is unknown, add ten drops per quart of water. Double amount 
of chlorine 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 two gallons of water. 
The 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 to each 12.5 gallons of water to be disinfected. To remove any 
objectionable chlorine odor, aerate the water as described above. 

CHLORINE TABLETS. 

Chlorine tablets containing the necessary dosage for drinking water 
disinfection can be purchased in a commercially prepared form. These 
tablets are available 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. 

Iodine Methods -- The use of iodine as a means of disinfection may not 
be effective in guarding against exposure to Giardia or Cryptosporidium. 
Therefore, iodine use should be limited to the disinfection of well 
water (as opposed to surface water sources such as rivers, lakes, and 
springs), because well water is unlikely to contain these disease 
causing organisms. 

TINCTURE OF IODINE. 

Common household iodine from the medicine 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 at least 
30 minutes. 

IODINE TABLETS. 

Commercially prepared iodine tablets containing 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. 

WATER TO BE USED FOR DRINKING, COOKING, MAKING ANY PREPARED DRINK, OR BRUSHING
THE TEETH SHOULD BE PROPERLY DISINFECTED.


Environmental Protection Agency's Office of Water
August 1997

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