The Swiss-pioneered water-disinfection method SODIS is an incredibly simple, fast and effective way of turning contaminated water into safe, potable water. How? By simply leaving a clear PET plastic bottle filled with infected water onto a piece of metal out in the sun for 6 hours, enough time for UVA radiation to kill all bacteria, viruses and parasites. It’s helped countries like Tanzania and Kenya make its contaminated tap water safe, and school absenteeism due to diarrhea drop.

Source: The National Geographic