A group of researchers in South Africa has developed a filter that can purify water straight from the bottle.

南非一组研究人员发明出一种可直接在瓶子中使水净化的过滤器。

The filter looks like a tea bag but contains material that block harmful chemicals

It sits inside a tube that can be fitted on top of a bottle and purifies water as it is poured on a cup.

The designer behind the filter, Dr Eugene Cloete, from the Stellenbosch University in South Africa, says the filter is only as big as an ordinary tea bag.

He says the product is cost-effective（划算的） and easy to use.

"We are coming in here at the fraction（分数，部分） of the cost of anything else that is currently on the market," says Dr Cloete on BBC World Service.

According to him the filter will not only stop harmful bacteria（细菌） from getting into the water, it will also kill them.

"We cover the tea bag material with nano-structured fibres, and instead of tea inside the tea bag, we incorporate activated¹ carbon.

"The function of the activated carbon is to remove most of the dangerous chemicals that you would find in water."

He says that the function of the fibres is to create a filter where harmful bacteria is physically² filtered out and killed.

Better taste

According to the World Health Organisation³ the number of people who can access clean drinking water has been improving steadily⁴ across the globe. But there are millions of people - many in Sub-Saharan Africa - who still do not have access to drinkable water.

The filter will also improve the taste of the water says Dr Cloete. "If you take ordinary tap water that you get in the city," he says, "that is chlorinated（含氯的） for instance."

But with the new filter, "the activated carbon will remove the chlorine so the water will actually taste better," he says.

Dr Cloete says his team wants to have an impact on 1.2 billion people around the world who do not have access to safe drinking water.

He says there have been extensive interest about the filter since the invention was announced.

"We have had many, many inquiries⁵（打听，询问） from aid organisations and from philanthropists（慈善家） who are quite prepared to sponsor these filters to people that need them most," he says.

But there are also commercial potentials, "for those people who go camping and those people who go hiking and so on," he adds.