VOA慢速英语 图书馆地下室为穷人制作水过滤器

　　Tests have shown that the filter produces safe drinking water.

　　On a good day, Jeffrey Schwarz says the studio in the library can produce twenty filters. To make one, clay is mixed with a material that burns. It could be sawdust or agricultural waste like grain hulls, cocoa or coffee shells. Pine needles can also be used.

　　The mixture is shaped into a cone and then fired. Burning away the material added to the clay leaves tiny holes. These holes let water slowly pass through the walls of the filter.

　　A protective coating of colloidal silver is painted on the inside and outside of the filter to kill bacteria. Colloidal silver is made from water with microscopic particles of silver.

　　The water filter costs little to make. An international service project called Pure Water for All helps support the work. The Forest Hills Rotary Club in western Pennsylvania launched the project. The project Web site is purewaterforall.org.

　　Jeff Schwarz will end his service for AmeriCorps soon. But he plans to continue making the water filters in the depths of the library.

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