New gadget for water purification: a 'nano tea bag'

August 18, 2010 by Lin Edwards report
teabag
Source: wikipedia

(PhysOrg.com) -- Scientists in South Africa have come up with a novel way of purifying water on a small scale using a sachet rather like a tea bag, but instead of imparting flavor to the water, the bag absorbs toxins, filters out and kills bacteria, and cleans the water.

The bag, which fits into the neck of an ordinary water bottle, was developed by scientists at Stellenbosch University in South Africa to help communities with no facilities to clean their water. The bags are made of inexpensive tea bag material but instead of containing tea they contain nano-scale antimicrobial fibers that filter out contaminants and microbes, and granules of activated carbon that kill the bacteria. The nano-fibers are about one hundredth the width of a human hair.

According to researcher Marelize Botes, one sachet can clean a liter of the dirtiest water to about the same water quality of bottled water. Once the bag has been used it is discarded and a new bag is fitted in the neck of the bottle. The discarded bags have no environmental impact as they disintegrate in only a few days and the materials are not toxic to humans.

Inventor of the filter, Dean of the Faculty of Science at Stellenbosch University, Professor Eugene Cloete, who is a microbiologist, said the filter presents a decentralized, point-of-use technology. As such it should find acceptance in the places where it is needed and where there is insufficient infrastructure for piped water. Professor Cloete specializes in water quality, water resource management and the use of nanotechnology in water applications. He is also director of the University of Pretoria's Water Institute and a senior fellow of the Water Institute of South Africa (WISA).

The sachet filter is still being tested by the South African Bureau of Standards, but Botes said early testing on samples of near the university were successful. The bags are expected to be available by the end of the year at a cost of about half a US cent (three South African cents) per bag, which makes it affordable even for poor communities in Africa, where millions of people do not have access to clean drinking water, and where water-borne diseases are a major problem.

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TwoBears
5 / 5 (1) Aug 18, 2010
In the article on the Nano Tea bag it was assumed that granulated activated carbon particles are capable of killing bacteria. I do not believe that this is accurate and, in fact, many carbon beds will actually promote the growth of microorganisms and deposit bacterial slime, though these microbes are generally nonpathogenic.
danman5000
5 / 5 (2) Aug 18, 2010
Fantastic idea, but what's to stop the nano-sized fibers from leaking right out of the bag through the (relatively) enormous holes?
Bowinja
not rated yet Aug 18, 2010
Generally, you should not need to worry about bacterial growth within the activated charcoal because the filter is discarded after filtering 1 liter of water, and the filtering process should be relatively short compared to the length of time when bacterial growth is a concern.

Additionally, if the activated carbon is swallowed it is non-toxic and continue to bind the toxins previously attached allowing them to pass from the body without absorption.
Shootist
1 / 5 (2) Aug 18, 2010
In the article on the Nano Tea bag it was assumed that granulated activated carbon particles are capable of killing bacteria. I do not believe that this is accurate and, in fact, many carbon beds will actually promote the growth of microorganisms and deposit bacterial slime, though these microbes are generally nonpathogenic.


And you are correct. But activated carbon does sequester bacteria and if treated with silver nitrate will kill most offending animacules.
jwalkeriii
not rated yet Aug 18, 2010
This is pretty exciting news, but how about heavy metal contaminants and other nasty contaminants?
stealthc
1 / 5 (2) Aug 18, 2010
If there is poison in the water, it'll still be poisonous. Boiling your water is more affordable and does the same. I wouldn't trust just any water through this device.
jwalkeriii
5 / 5 (1) Aug 19, 2010
Boiling water is not always an option, and I understand that in outlying areas heavy metals are not an issue. But still, muddy water, is well... muddy, bacteria or no.

Sure like to hear more details on what it does not do.
Javinator
not rated yet Aug 19, 2010
one sachet can clean a liter of the dirtiest water to about the same water quality of bottled water


What do they mean by "the dirtiest water"?

I'd also like to know how much time it would take to filter/clean the water. It would seem as though the time would be dependant on the "dirtiness" of the water so it might be difficult to actually know when your water is clean.

Maybe if they included instructions for how long it would take to clean a litre of "the dirtiest water", but again that would need to be defined.

Great idea though. With that kind of price/bag it's feasible that people in developing nations could start drinking cleaner water in the very near future.
carbon_carbon
not rated yet Aug 22, 2010
I found a site the university put up.
www.thehopeproject.co.za/water

This is an admirable project. I don't have much to spare, but this can really help so many, so I'll try to donate.
jwalkeriii
not rated yet Aug 22, 2010
The link above has no links to this this subject matter, other than linking to a charity site, and can be ignored.

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