Each page is impregnated with silver nanoparticles (which gives the paper its distinctive orange colouring). The nanoparticles don’t quite work like a traditional filter. Rather than providing a barrier, they actually kill the bacteria as they pass through the paper. As the water runs through, the bacteria absorb the silver ions, which kill the bacteria. The paper kills over 99.9 percent of harmful bacteria, which puts the resulting water on a par with tap water in the US. It has proven effective at destroying bacteria that cause diseases such as cholera, E.coli and typhoid.