The SODIS process involves filling transparent
plastic bottles with water and exposing them to
full sunlight for six or more hours so that a
combination of UV-A radiation and increased water
temperature disinfects the water. This process may
be combined with solar reflectors or solar cookers
to further increase water temperature.
The Swiss Federal Institute for Environmental
Science and Technology
"We do not recommend any more to paint the plastic
"UV-A transparent bottles of 0.3 - 3 litres can be
used for SODIS. The bottles also reduce the risk of
a recontamination of the treated water as long as
the water is stored in the bottle, consumed
directly from the bottle and/or from a clean glass.
I kindly ask you to disseminate this information
order to avoid misleading recommendations."
Amount of Water Treated
SODIS requires 10 or fewer liters of water per
container in order to be effective. The size and
number of bottles used, as well as the length of
exposure required given the sun’s availability,
will determine the amount of water treated by
SODIS, without the use of reflectors or cookers,
has been found to kill 99.4 percent of fecal
coliform in a liter of water with one day of full
light exposure and 91 percent under cloudy
conditions. These removal rates heavily depend on
sunlight intensity and duration, cloudiness,
ambient temperature, and bottle quality, including
how scratched and thick the plastic is. Removal
rates for SODIS are lowered by the presence of
organic matter, iron, sulfites, nitrites, and
turbidity because these particles absorb UV
radiation and shield microbes from being hit with
UV rays. UV radiation does not treat chemical
contamination or turbidity.
Ease of Use
SODIS is a very simple process to set-up, though
SODIS users need to monitor the temperature of the
water to ensure it is properly treated.