An estimated 600 to 700 million people around the world are at risk of disease or even death because their drinking water is not clean. The water is infected with harmful bacteria or other contaminants.

But researcher Teri Dankovich has developed a special book that could turn dirty water into clean, drinkable water.

The book contains 25 pages. Each page is about one millimeter thick. The pages contain very small particles of silver. The pages can be used as filters to remove harmful microorganisms that can pollute drinking water. The filter kills the organisms that pass through it.

Ms. Dankovich says each page can treat up to 100 liters of water.

Pictures on the pages show the dangers of dirty water and how to use the book for those unable to read. The pages are made of filter paper. They are designed to be torn from the book. Water can be poured through the paper to be decontaminated.

Teri Dankovich and another researcher tested the drinkable book in Bangladesh, Ghana and South Africa. The tests proved to be successful.

Ms. Dankovich recently presented her invention at the meeting of the American Chemical Society in Boston, Massachusetts. She was asked whether she has considered adding classic literature on the book's pages.

"The idea of classical texts - that's of interest maybe later. But we have discussed a little bit more exciting text. But we really haven't had the time to go through that part," she says.

Water for Life, a non-governmental organization, has provided financial support for the project.

I'm Jonathan Evans.