Filters are a convenient, inexpensive way to purify water in developing countries. But a University of Virginia-based nonprofit humanitarian organization called PureMadi -- "Madi" is the Tshivenda South African word for "water" -- has come up with an additional easy-to-use technology that can purify a container of water simply by being immersed in it [source: Samarrai]. The MadiDrop is a small ceramic disk, about the size of a hamburger patty, which contains microbe-killing silver or copper nanoparticles. Nanoparticles are basically really, really tiny objects specially designed by scientists to behave as a single unit [sources: Samarrai, Mandal].
The MadiDrop is cheaper, easier to use, and easier to transport than the larger ceramic flowerpot filters (pictured on the first page) that PureMadi already is making in an African factory, according to James Smith, a civil and environmental engineer who is one of the project's leaders. The one downside, again, is that the MadiDrop doesn't remove suspended particles that make water cloudy. So ideally, users will put water through a two-step purification process, by first using the flowerpot filter to get rid of sediment and then eradicating the microbes with MediDrop [source: Samarrai].