98 Protec ting Communit y Water
Howbtconbdxniscibnfect water with sunlight
Solar disinfection is an effective way to disinfect water with only sunlight and a
bottle. Filtering or settling the water first will make it clearer so it will disinfect more
quickly. Solar disinfection works best in countries close to the equator, because
the sun is strongest there. The farther north or south you are, the
more time is needed for disinfection to work. (For more information
about solar disinfection, see Resources.)
➊ Clean a clear plastic or glass bottle, or a plastic bag.
Bottles made of PET plastic work best.
➋ Fill the bottle half full, then shake it for 20 seconds. This will add air
bubbles to the water. Then fill the bottle or bag to the top.
The air bubbles will help to disinfect the water faster.
➌ Place the bottle where there is no shade and where
people and animals will not disturb it, such as the roof of
a house. Leave the bottle for at least 6 hours in full sun,
or for 2 days if the weather is cloudy.
➍ Drink directly from the bottle. This will prevent contamination from hands or
other vessels.
Solar disinfection can be done faster and more completely by putting the bottle
in a solar cooker (see page 364).
Use 1 lime or
lemon for every
liter of water.
Lime or lemon juice
Add the juice of a lime or lemon to 1 liter of
drinking water and let it sit for 30 minutes. This
will kill most cholera and some other germs as
well. This does not make water completely safe,
but is better than no treatment in areas where
cholera is a threat. Adding lime or lemon juice
to water before using solar disinfection or the
3-pot method will make the water safer.
Chlorine
Chlorine is cheap and easy to use to kill most germs in drinking water. But if
too little chlorine is used, it will not kill germs. If too much is used, the water
will taste bad. Chlorine is best used in community water systems, because it can
be difficult for a single household to do it well all the time. To use chlorine to
disinfect household water, follow the instructions on the next page.
Large amounts of chlorine are harmful to people and the environment, but
the amounts used to disinfect home and community water are generally safe.
It is safer to disinfect water with chlorine than to risk the health problems
caused by germs.
A Community Guide to Environmental Health 2012