A "book" containing pull-out pages that can save lives by making polluted water drinkable has been developed by scientists.
Each page of The Drinkable Book, as it is known, is impregnated with bacteria-killing silver and copper nanoparticles.
In tests conducted in Africa, it made water contaminated with raw sewage as safe as North American tap water.
Designer Dr Theresa Dankovitch, from Carnegie Mellon University in the US, said: "In Africa, we wanted to see if the filters would work on 'real water', not water purposely contaminated in the lab.
"One day, while we were filtering lightly contaminated water from an irrigation canal, nearby workers directed us to a ditch next to an elementary school, where raw sewage had been dumped. We found millions of bacteria; it was a challenging sample.
"But even with highly contaminated water sources like that one, we can achieve 99.9% purity with our silver and copper nanoparticle paper, bringing bacteria levels comparable to those of US drinking water.
"Some silver and copper will leach from the nanoparticle-coated paper, but the amount lost into the water is within minimal values and well below Environmental Protection Agency and World Health Organisation drinking water limits for metals."
Last year Dr Dankovitch formed a non-profit company, pAge Drinking Paper, to manufacture the book.
Each page can be removed and slid into a special holding device through which water is poured and filtered. One page of the book can clean up to 26 gallons of drinking water.
An entire book has the potential to filter one person's water for four years.
She is now further developing the technology with a view to producing a commercial nanoparticle filter for household water treatment.
Dr Dankovitch spoke about The Drinkable Book at the American Chemical Society's national meeting in Boston.