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'Tea bag' filter delivers purified water

27 July 2010

Combining years of research on water purification, food microbiology and nanotechnology, scientists at South Africa's Stellenbosch University have developed a high-tech "tea bag" filter that fits into the neck of a bottle and turns polluted water into clean water as you drink from it.

It promises to provide easy access to clean drinking water for vulnerable communities, for instance those living near polluted water streams. There are also plans to commercialise the filter bag into a product that can be used by outdoor enthusiasts on hiking or camping trips.

When microbiologist Professor Eugene Cloete became Dean of the Faculty of Science at Stellenbosch University (SU) in January 2009, he picked up on relevant research outside his own field of expertise, which sparked the invention of a high-tech disposable filter that looks like a tea bag and cleans highly polluted water.

Together with researchers from the Department of Microbiology and SU polymer scientists, he recently patented the innovative invention –a portable, easy-to-use, environmentally friendly water filter bag that fits into the neck of a bottle.

"The water is cleaned right then and there when you drink from the bottle," Cloete said in a statement issued by the university last week.

Water provision, sustainability

As a past executive vice-president of the International Water Association and a member of Coca-Cola's worldwide panel of water experts, Cloete believes water provision and sustainability go hand in hand.

"The lack of availability of adequate, safe and affordable water supplies impacts severely on vulnerable groups such as the poor, the elderly, HIV/Aids patients and children," he said.

"More than 90% of all cholera cases are reported in Africa, and 300-million people on our continent do not have access to safe drinking water. Clearly, something has to be done about this."

Cloete believes the "tea bag" filter shows the way forward because it represents decentralised, point-of-use technology. It can help meet the needs of people who live or travel in remote areas, or people whose regular water supply is not being treated to potable standards.

"It is simply impossible to build purification infrastructure at every polluted stream. So we have to take the solution to the people," he said.

Trans-disciplinary initiatives

The invention has become one of the first major projects of the new Stellenbosch University Water Institute, a trans-disciplinary initiative established to intensify the search for lasting solutions to the country and continent's water woes.

Cloete, who is the chairperson of the Water Institute, says he got the idea for the filter on an introductory visit to InnovUS, the university's technology transfer company, some 18 months ago.

"I was shown the electro-spinning technique of spinning ultra-thin fibres on a nanoscale developed by Dr Eugene Smit of the Department of Chemistry and Polymer Science," he said.

"Right away, my mind started churning through the possibilities of how it could be used to clean polluted water."

'Off-the-shelf materials'

A research team was put together and, after various trials and experiments, a filter sachet was developed that not only resembles a tea bag in shape and size, but is made of the same biodegradable material as off-the-shelf rooibos tea bags:

• The inside of the tea bag material is coated with a thin film of biocides encapsulated within minute nanofibres, which kills all disease-causing microbes.
• The bag is filled not with tea leaves but with active carbon granules that remove all harmful chemicals, for instance endocrine disruptors.
• Each "tea bag" filter can clean one litre of the most polluted water to the point where it is 100% safe to drink.
• Once used, the bag is thrown away, and a new one is inserted into the bottle neck.

"We tested the filter with water taken from a river here in the Stellenbosch area. The samples were highly polluted with pathogens, but they came out completely clean on the other side," said Dr Michéle de Kwaadsteniet, a postdoctoral fellow working on the project with Cloete and Professor Leon Dicks of the Department of Microbiology.

The "tea bag" filter is currently being tested by the South African Bureau of Standards, after which the team hopes to roll it out to various communities.

"It really is exciting to be part of a potentially life-changing project," said Dr Marelize Botes, postdoctoral fellow in the Department of Microbiology and a member of the water filter bag research team. "It's such an easy-to-use and practical solution to something that’s been a major problem for so long."

HOPE Project

The Stellenbosch University Water Institute and its "tea bag" water filter form part of its HOPE Project, a set of development goals aimed at improving lives in South Africa and the rest of the continent.

"We firmly believe that science should serve the needs of society. By aligning the expertise of our scientists with the national and international development agenda, we want to become more relevant to society," said Professor Russel Botman, rector and vice-chancellor of the University.

SAinfo reporter