Anybody heard of this? - Solar Water Disinfection Process

Bluster · Coal Joined: Nov 28, 2004 Posts: 11

Bottle it up

In northern Brazil, residents in the town of Oroba are using an altogether different method in order to purify water and prevent disease.

The town's inhabitants have taken to a surprisingly simple process called Sodis (Solar Water Disinfection Process).

There are several stages to Sodis. Firstly, a clean, two-litre bottle needs to be filled up to three-quarters of its volume with water.

The bottle is shaken for 20 seconds to oxygenate the water. Then, the rest of the bottle is filled and the top screwed on.

Sodis is particularly suitable for communities on the equator
It is then placed on a rooftop in direct sunlight for six hours. The ultraviolet (UV) radiation from the Sun's rays eliminates virtually all disease-causing bacteria, viruses and micro-organisms.

"This method is very efficient if you follow the simple procedures," says Professor Jose Euclides Paternini of the Unicamp University, Sao Paolo.

"The Sodis method can be used in many countries, but especially those close to the equator with high solar radiation, and where the population has no access to conventional water treatment."

Luiz Barbosa has been a community health worker for 10 years, looking after 118 families in Oroba. He has observed the difference Sodis has made to the health of his community.

"The water treatment we are using here in this municipality is Sodis - that is purification through the Sun's rays - and it is working well because the children are healthy, smiling and they're enjoying a healthier life," he explains.

SODIS

savethehumans · Light Sweet Crude Joined: Oct 20, 2004 Posts: 1541

If this is so, then it'll be VERY useful in providing potable water in the Post-Peak, Post-Die-Off world! Thanks for the input! Smile

Bluster · Coal Joined: Nov 28, 2004 Posts: 11

You are welcome Embarassed

Terran · Posted: Mon Nov 29, 2004 12:50 am Post subject:

Very useful, this seems really ideal. I think for regions that don't get intense sunlight you can concentrate the beam of sunlight using reflectors, this causes an increase in light intensity, therefore should increase the power of the UV rays.

Or you can concentrate the sunlight, and bring the water to a boil using solar energy, but UV is a better option.
_________________
my page:
www.myspace.com/peakoil

Laocoon · Coal Joined: Nov 28, 2004 Posts: 1

Sol-Air Water Treatment
If sufficient dissolved oxygen is available, sunlight will cause the temporary formation of reactive forms of oxygen such as hydrogen peroxide and oxygen free radicals. This form of water treatment is called solar photooxidative disinfection or sol-air water treatment. Sol-Air water treatment has been shown to dramatically reduce the level of fecal coliform bacteria. There is some evidence that other bacteria and viruses may be affected also. While not as reliable as other methods, it does offer a low-tech solution in emergencies. Sol-Air treatment requires bright sunlight, and has been shown to be effective when ever the sun causes a distinct shadow to be cast. Exposure to 4.5 hours of bright sunlight has been shown to cause a thousand fold reduction in fecal coliforms in lab tests
In order for Sol-Air to be effective, oxygen must be present. Experiments have shown that shaking a bottle filled 3/4 with air will restore oxygen levels to near saturation. As the treatment continues, some of the oxygen will come out of solution, while other oxygen will be consumed by the killed pathogens, so the shaking should be repeated every few hours. Data shows that maximum activity occurs when the water temperature is above 50Â° C (122Â° F), so this method may be unsuitable in colder climates unless special solar collectors are used.
Either glass or plastic bottles may be used. Plastic bottles will allow short wave ultraviolet radiation to pass, increasing the rate of microbial inactivation, but may yellow with age, reducing light transmission, and may leach plasticizers into the water at the elevated temperatures that will occur. The leaching of plasticizers can be reduced by using bottles of PET (polyethlyene terephtalate) rather than PVC. Glass bottles on the other hand are more durable. Research has used bottles with 2 liters of capacity, but if the water is free of turbidity, larger containers can be used. Plastic bags, or some sort of flat glass container represent the ideal container as this maximizes the solar energy received per ounce of water.
Bottles should be filed 3/4 full in the early morning with water as free of turbidity as possible. After capping the bottles should be shaken vigorously for a few minutes then placed upright in the sun, where they will be not be shaded later in the day. The shaking should be repeated at least three times during the day. At the end of the day the water should be reasonably freed of bacteria, though it is most practical to let the water cool for consumption the following day. Each day a new batch should be treated due to the lack of a residual disinfected.
After consumption of the water the bottle should be air dried to prevent algae growth with continual use.