Scallop Shells for Water Purification.

James Beaton-Johnson, Elias Fares and Amy Trottier, three J.L. Ilsley high school students discovered a cheap and effective way to clean up dirty water:

The trio got the idea from a documentary about a Japanese fish farmer who tossed oyster shells into a pond and found it cleared the dirty water.

The students at J.L. Ilsley high school began experimenting with scallop shells immersed in dirty dish water. The water cleared in 24 hours.
Elias Fares, James Beaton-Johnson and Amy Trottier claimed second prize in the Aventis Biotech ChallengeCourtesy: BioNova

They discovered the shells' shape and chemical makeup neutralizes pH and also helps filter out coliform bacteria, sediment and heavy metals.

http://www.cbc.ca/story/news/national/2002/11/15/water_scallops021115.html (via digg)