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Nanotech and 'tea bag' to clean up drinking water

Half of the hospital patients in the developing world are suffering from sanitation and water-related diseases, says the UN.
Half of the hospital patients in the developing world are suffering from sanitation and water-related diseases, says the UN.
  • New water filter systems use nanotechnology to make water safe for drinking
  • One new development is similar to a tea bag; one bag makes one liter of clean water
  • The inventor of the "tea bag" device hopes it will bring safe water to millions
  • Another filter device uses silver to purify contaminated water

(CNN) -- Lack of access to clean water is still a problem for millions of people across the world, but new developments in nanotechnology and a water filter that resembles a humble tea bag could prove to be effective solutions.

The "teabag" filter is the brain-child of Professor Cloete of Stellenbosch University.

It is designed to fit in the neck of a standard sized water bottle, meaning it is interchangeable, and, depending on the quality of water being filtered, costs between one and five cents per liter.

"The easiest way to visualize our filter is to think of a normal tea bag," said Cloete.

"The outside of the bag is coated in a polymer that includes a biocide, which means that it both filters water and kills bacteria -- we haven't yet come across a bacteria it can't kill.

The top end can sponsor the bottom end, and by paying this people could make a difference to millions.
--Professor Cloete, inventor of 'tea bag' water filter

"While the inside -- the tea, if you like -- is made of activated carbon, which can remove chemical pollutants.

"It's easy to remember: one bag, one liter."

The bags are disposable and fully biodegradable and, according to Cloete, the activated carbon inside "is a good soil conditioner."

"All technology has its limitations," says Cloete. "I wouldn't drink sewage water through it. But if you take very heavily contaminated water -- with one million bacteria per milliliter -- it will reduce that to less than ten; you just can't find them after it's been through the filter."

Professor Cloete is currently working with machine manufacturers in the Czech Republic and hopes to have a mass-market version available by February 2011.

He says he has already been "inundated" with requests from NGOs for tea bags to distribute in various areas around the world. According to the UN's World Health Organization lack of clean water and sanitation kills 1.6 million children each year.

"The tea bag water filter technology sounds good especially from the point of it being one step process, with out having to do any mixing," said Nega Bazezew Legesse of Oxfam.

"One possible limitation is that the tea bag is used only once to produce one liter of drinking water. How many of the tea bags will be need for a family per day is difficult to answer... it has to be very, very cheap."

Although even a low-cost could be an issue for those living on a dollar a day, or less, Professor Cloete believes that a small surcharge to sales in the West could help subsidize costs in the developing world.

"The top end can sponsor the bottom end, and by paying this people could make a difference to millions," he said.

The "teabag" isn't the only interesting filtration tech on the horizon, and researchers in California are developing a filter that uses nanotech and silver to produce clean water.

It works using a mesh made from a combination of tiny carbon cylinders -- known as nanotubes -- and silver wire. Silver is known to kill bacteria, but the addition of an electric current makes the process even more effective, killing up to 98% of bacteria.

"The bacteria concentration after filtration depends on the initial concentration of bacteria in water," said developer Dr Cui of Stanford University.

"If the initial concentration is too high, one may need to do more times of filtration using the device now we have. However, we are trying to optimize our filter to make it more effective. And maybe after only one filtration you will get 'safe' water."

Although a commercial version is some way off, Dr Cui believes there could be a mass-market version of his technology available.

"It could be commercialized," he said. "I think it will definitely be affordable for people in developing countries. Moreover, if you consider cost, you will need to consider the lifetime of the device as well. It is not a one-time expense because our filter is reusable."

The power needed to run the filter can be provided by any device that can provide 20 volts, such as a small solar panel. Dr Cui hopes in the future only a 9-volt power source will be needed.

For Legesse and Oxfam, the main issue with nanotechnology solutions is that they are affordable and can be replicated at a low cost in developing countries.

"But we feel such innovations will make a difference to our endeavor to supply potable water in our programs, and we would like to see a successful outcome from the research work," he said.


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