Screw filter on bottle and drink clean water

Imagine screwing a water filter onto a bottle containing polluted water and voila - you can put it straight in your mouth and drink.

German researchers have developed a water filter prototype that can be fitted on to virtually any plastic bottle.

"It does not require a pump or a reservoir, so it is very easy to use," said Jeremy Nussbaumer, a mechanical engineering student from ETH Zurich (Eidgenossische Technische Hochschule Zurich).

Weighing less than 100 grams, DrinkPure is considerably lighter than most other filters.

The flow pressure is so high that you can purify as much as a litre of water in a minute just by squeezing the bottle with your hand.

"Another benefit is that the unit is less expensive and easier to manufacture than most conventional filters," Nussbaumer noted.

Three filtering stages make DrinkPure one of the most reliable devices.

First, a pre-filter captures large particles such as sand and plant fragments.

The second stage consists of an activated charcoal powder that primarily removes undesirable odours and chemical contaminants.

And the third and most important part of the filter is a polymer membrane that removes bacteria.

Working with researchers from a group led by Wendelin Stark, head of the Functional Materials Laboratory at ETH, the 23-year-old Nussbaumer spent a year researching a membrane filter and developing a prototype.

The device is also perfect for travellers and walkers.

Researchers expect to have the first filters completed in January 2015 which will be sent to Africa for use in a test phase.