- Joined
- Aug 15, 2000
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- 135
This article from the current issue of 'New Scientist' in the UK may be of interest (sorry if it's old hat in the US!):
A PLASTIC bottle provides a cheap way to harness the power of the Sun to disinfect emergency supplies of drinking water after natural disasters.
This week Oxfam discussed using solar disinfection in Assam, India, where the floods earlier this month left 5 million people homeless. The charity says that chlorination tablets for disinfecting drinking water are in short supply.
The idea of using plastic bottles for solar disinfection--or SODIS--has been developed by researchers at the Swiss Federal Institute for Environmental Science and Technology in Duebendorf. To disinfect water, people simply fill clear plastic bottles with water and leave them in the sun. The heat warms up the water and the combination of warm water and ultraviolet radiation kills most microorganisms.
"SODIS efficiently inactivates bacteria and viruses," explains project leader Martin Wegelin. He says that tests have shown that 99.9 per cent of the Escherichia coli in a sample of contaminated water were killed when the sun heated the water beyond 50 °C.
At this temperature, the process can take as little as an hour, says Wegelin. Painting half the bottle black and laying it on a corrugated metal sheet shortens the time taken to warm up the water.
Wegelin and his colleagues have been testing the effectiveness of SODIS in several rural parts of Asia, Africa and South America, where water-related illnesses claim 5 million victims every year. The results are encouraging. SODIS is particularly good at killing Vibrio cholerae, the bacterium that causes cholera. SODIS also inactivated some common human parasites such as cryptosporidium that cause severe diarrhoea.
The technology could also be a boon in the developing world's growing urban areas, where water supplies are often contaminated--as a result, sales of bottled drinks are soaring among the rich. "The target population of the soft drinks industry are well off people who buy the bottles. The target population of SODIS are the poor who are interested in empty bottles," he explains. "Bottles go from rich to poor, reducing the waste in urban areas."
Their idea does have its drawbacks, says Tricia Jackson of the water engineering and development centre at Loughborough University. "There may be a lack of suitable plastic containers in emergency areas," she says. Alan Reed of Oxfam says that the main problem is the absence of education about hygiene. "If there is little water and people have to travel a long distance to get it, they don't tend to worry what it contains."
But Wegelin is optimistic that with proper education, people will use SODIS. Wegelin says that in a trial of SODIS, 84 per cent of people said they would continue to use it. "We are now in the process of promoting SODIS at a national level in Asia and South America."
The link is:
http://www.newscientist.com/nlc/0826/solar.html
Mark
A PLASTIC bottle provides a cheap way to harness the power of the Sun to disinfect emergency supplies of drinking water after natural disasters.
This week Oxfam discussed using solar disinfection in Assam, India, where the floods earlier this month left 5 million people homeless. The charity says that chlorination tablets for disinfecting drinking water are in short supply.
The idea of using plastic bottles for solar disinfection--or SODIS--has been developed by researchers at the Swiss Federal Institute for Environmental Science and Technology in Duebendorf. To disinfect water, people simply fill clear plastic bottles with water and leave them in the sun. The heat warms up the water and the combination of warm water and ultraviolet radiation kills most microorganisms.
"SODIS efficiently inactivates bacteria and viruses," explains project leader Martin Wegelin. He says that tests have shown that 99.9 per cent of the Escherichia coli in a sample of contaminated water were killed when the sun heated the water beyond 50 °C.
At this temperature, the process can take as little as an hour, says Wegelin. Painting half the bottle black and laying it on a corrugated metal sheet shortens the time taken to warm up the water.
Wegelin and his colleagues have been testing the effectiveness of SODIS in several rural parts of Asia, Africa and South America, where water-related illnesses claim 5 million victims every year. The results are encouraging. SODIS is particularly good at killing Vibrio cholerae, the bacterium that causes cholera. SODIS also inactivated some common human parasites such as cryptosporidium that cause severe diarrhoea.
The technology could also be a boon in the developing world's growing urban areas, where water supplies are often contaminated--as a result, sales of bottled drinks are soaring among the rich. "The target population of the soft drinks industry are well off people who buy the bottles. The target population of SODIS are the poor who are interested in empty bottles," he explains. "Bottles go from rich to poor, reducing the waste in urban areas."
Their idea does have its drawbacks, says Tricia Jackson of the water engineering and development centre at Loughborough University. "There may be a lack of suitable plastic containers in emergency areas," she says. Alan Reed of Oxfam says that the main problem is the absence of education about hygiene. "If there is little water and people have to travel a long distance to get it, they don't tend to worry what it contains."
But Wegelin is optimistic that with proper education, people will use SODIS. Wegelin says that in a trial of SODIS, 84 per cent of people said they would continue to use it. "We are now in the process of promoting SODIS at a national level in Asia and South America."
The link is:
http://www.newscientist.com/nlc/0826/solar.html
Mark
