Water Purification @ Zero Cost !

shanthi

Kevin McGuigan is a Senior Lecturer in Medical Physics in the
Royal College of Surgeons in Ireland. His research examines
the use of solar disinfection of drinking water for use in
developing countries. In Sub-Saharan Africa 769000 children
under 5 years of age, died annually from diarrhoeal diseases
in 2000-2003.
Solar Disinfection (SODIS) is a technique for making
contaminated drinking water safe where transparent bottles are
filled with biologically contaminated water and placed in
direct sunlight for 6 hours. SODIS reduces faecal
contamination levels from 1 million bacteria per ml to zero in
less than 1.5 hours and is completely effective against the
pathogens responsible for cholera, dysentery, typhoid,
giardiasis, salmonella, gastroenteritis, and polio. Clinical
trials run by the R.C.S.I. have shown that Kenyan children
under 5 years using SODIS were 7-times less likely to contract
cholera than children who had not. Other intervention
technologies require funds beyond the financial resources of
the communities that need them most. No such limitations apply
with SODIS which is a sustainable zero-cost technology that
requires only a plastic bottle and moderate levels of
sunlight. SODIS was approved by the WHO in January 2005
immediately after the Asian Tsunami.

Nick-H

Just sunlight?

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Jorge Reverter

Hi Shanthi,

First time I've heard about this matter. If things are so easy, these are really good news for the third world.

The_blue

It's the UV rays. Simple idea but a great idea!

shanthi

JUST sunlight! This aint a spoof, it's the REAL job. tries and tested and sampled....good idea for ANYONE travelling in India or elsewhere - where there is sun in good measure - as the blue said - SO simple - yet it WORKS!!

Nick-H

But my unscientific experience of leaving water in the sun is that green stuff grows in it.

shanthi

you'd only be leavin' it for the specified period nickbhen

john.sw

We have spring water at our house in the UK - municipal water is not available, and our private natural springs produce very good water.

Ultraviolet filters are available (in India and the UK) to kill bacteria in the water, so ultraviolet must work!

But we know that the usual contaminants, such as E-coli, Cryptosporidium, Shigella, Salmonella and Giardia thrive in warm conditions.

I would not recommend drinking contaminated water, even if it had been in a transparent bottle in the sun for 6 hours.

It would be like taking a laxative and Imodium at the same time and betting on which one wins!

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Anders

It actually does seem to work.
http://www.sodis.ch/
http://www.who.int/water_sanitation_...en/index4.html

katyrafi

http://www.who.int/water_sanitation_...en/index4.html states:

Treatment of water with solar radiation was practiced in ancient India more than 2000 B.C.E.


Note the following steps to get it right:

(1) removing solids from highly turbid (>30 NTU) water by settling or filtration, if necessary, (2) placing low turbidity (<30 NTU) water in clear plastic bottles of 1-2 liter volume (usually discarded beverage bottles and preferably painted black on one side), and (3) aerating (oxygenating) the water by vigorous shaking in contact with air, and (4) exposing the filled, aerated bottles to full sunlight for about 5 hours (or longer if only part sunlight).

And interestingly:

Overall, studies have shown that various bacteria, such as fecal coliforms, E. coli and enterococci, and viruses, such as coliphage f2, rotavirus and encephalomyocarditis (EMC) virus, in water bottles are reduced extensively (by several orders of magnitude) when exposed to sunlight for periods of several hours and sufficiently high temperatures are achieved.

The simplest ideas are always the best!! What a brilliant link, thanks for finding that Shannti & Anders

AvidTrekker

This was a continuing tradition till as recently as sixty years ago. Old timers used to expose water stored in Copper containers and exposed them to sunlight. Effects were better with copper than with sunlight alone.

Those with a little better financial standing did the same with silver. Effects even better. One mahaaraajaah [of Vaaraanasi?] actually took a few big sized [man could be fitted inside] silver urns containing Gangaa river water on his ship voyage to England. If I remember well, NASA uses silver globules to purify water in outer space.

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shanthi

Wow, that's interesting AT, but I can't imagine putting water into copper urns - wouldn't yoou think the water would taste even more tainted? Not that I'm a scientist about this sort of thing though. And silver would be best? Shame that's not stainless steel eh? there's sure plenty of that in India!

Nick-H

Silver has long been known to be antimicrobial

AvidTrekker

There is a bit of a metallic tang to the water. I have been drinking water from a copper vessel for as long as I know anything. But not drenched in sunlight. [the vessel might get stolen, which is why...]Ten/twelve years back, I recall that there was a sudden rush to this re-discovered concept. A lot of copper vessels of different capacities started becoming available. But these copper vessels must be washed sparkling clean every third day or so; such that only metallic copper touches the water and not the blue-green coloured cupric oxides [which are mildly poisonous]
Silver is the best. Better than gold. NASA uses it.
What does Nickbhen mean? At least in Gujaraatii, Nickbehn means Nick-sister and Nickbhai means Nick-brother. Bhai itself with a certain drawn out accent means a "brother" [of the mafia family]

Jeroen

>One mahaaraajaah [of Vaaraanasi?] actually took a few big sized [man could be fitted inside] silver urns containing Gangaa river water on his ship voyage to England.

Jaipur - the urns are on show at the palace.

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