The MadiDrop is a cheap ceramic disk made of clay, sawdust, and water, and impregnated with silver or copper nanoparticles. The nonprofit that developed it says it is effective against 99.9% of pathogens that live in water.
The group, called PuriMadi, is a spin-off from the University of Virginia. Coleader James Smith, a civil engineer, says each disk lasts two to five years (based on a family of six using it) and costs about $5.
PuriMadi has already built a factory in the Limpopo province of South Africa and hopes to expand further. “Eventually that factory will be capable of producing about 500 to 1,000 filters per month, and our 10-year plan is to build 10 to 12 factories in South Africa and other countries,” Smith says. “We plan to eventually serve at least 500,000 people per year with new filters.”
The disk is one of two designs using similar technology. PureMadi also makes a flowerpot version, which is painted with a thin solution of silver or copper nanoparticles after firing. The water coming through the pot has a flow-rate of one to three liters per hour, and only trace metal particles are left in the water.
According to studies by the university’s medical school, the filters significantly improve "health outcomes for users and are particularly beneficial to people with compromised immune systems, such as people living with AIDS"--which has a 17 percent prevalence in South Africa. It should also help alleviate basic problems, like diarrhea, vomiting, and dehydration.