SU scientists develop a high-tech ‘tea bag’ filter for cleaner water

When microbiologist Prof Eugene Cloete became Dean of the Faculty of Science at Stellenbosch University (SU) in January 2009, he did not allow his expanded administrative duties to overwhelm his passion for his subject.

To the contrary, 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 and 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 explains.

The sachet combines years of fundamental research on water purification, nanotechnology and food microbiology in a practical way. 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.

As a past executive vice-president of the International Water Association and a member of Coca-Cola’s worldwide panel of water experts, Prof 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 says.

“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 says.

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

Prof 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 remembers.

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

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,” says Dr Michéle de Kwaadsteniet, a postdoctoral fellow. She is working on the project with Prof Cloete and Prof 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,” says 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.”

The Stellenbosch University Water Institute and its “tea bag” water filter form part of SU’s 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,” says Prof Russel Botman, Rector and Vice-Chancellor of the University.

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Africa’s vulnerable water supplies
• A water security risk index of 165 nations, released in June 2010, found that African and Asian nations had the “most vulnerable water supplies”, judged by such factors as access to drinking water, demand per capita and dependence on rivers that flow through other nations.

• African nations, led by Somalia, Mauritania and Sudan, have the most precarious water supplies in the world, while Iceland has the best.

• According to the index, climate change and a rising world population will increase stresses on supplies in coming decades, from agricultural to industrial uses.

Source: Maplecroft, a British-based risk consultancy firm,