You can disinfect small quantities of water in 2 ways:
- boiling (the simplest and best)
- chemical treatment.
Boiling water
Vigorous boiling for at least 1 minute will kill any disease-causing micro-organism present in the water.
The flat taste of boiled water can be improved by pouring it back and forth from one clean container to another.
Alternatively, allow it to stand for a few hours with a loose fitting cover.
Chemical treatment
When boiling is not practical, chemical disinfection can be used.
The simplest, most effective chemicals are chlorine and iodine.
Chlorine is generally more effective than iodine.
However, while they are both effective against most micro-organisms, including giardia, they may not be effective against cryptosporidium.
Chlorine disinfection
Water may be disinfected using household bleach containing chlorine (but not containing added perfumes or detergents).
Look for the percentage of available chlorine on the label and use the information in the following table as a guide to disinfect the water.
Table: Guide to chlorine disinfection of water
Available chlorine |
Drops per litre of clear water |
1 per cent |
10 |
4 to 6 per cent |
2 |
7 to 10 per cent |
1 |
The treated water should be mixed thoroughly and allowed to stand for 30 minutes.
The water should have a slight chlorine odour. If not, repeat the dosage and allow the water to stand for an additional 15 minutes.
The chlorine taste can be objectionable in treated water.
The taste can be made more pleasant by allowing the water to be exposed to the air for a few hours.
Alternatively, pour it several times from one clean container to another.
Granular calcium hypochlorite
Another option is to use swimming pool grade granular calcium hypochlorite.
Add, and completely dissolve, 1 heaped teaspoon of calcium hypochlorite in 7.5 litres of water.
This mixture will produce a concentrated chlorine solution of approximately 500 mg/L (milligrams per litre).
The concentrated chlorine solution can then be used to disinfect water in the ratio 1 part concentrated chlorine to 100 parts of water.
If using swimming pool grade granular calcium hypochlorite, always follow the instructions on the container in relation to safe handling and disposal of the product.
Chlorine tablets
Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased from pharmacies and sporting goods stores.
The tablets should be used in accordance with the manufacturer’s instructions.
Tincture of iodine
Common household iodine from a first aid kit may be used to disinfect water.
Add 5 drops of 2 per cent tincture of iodine to 1 litre of clear water.
If the water is cloudy add 10 drops of the tincture.
Let the solution stand for at least 30 minutes before drinking.
Iodine tablets
Commercially prepared iodine tablets containing the necessary dosage to treat drinking water can be purchased at a pharmacy or sporting goods store.
Iodine tables should be used in accordance with the manufacturer’s instructions.
Iodine is only suitable for short-term emergency use.
It should not be used repetitively or for longer than 1 week in any single emergency situation.