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The BioSand Water Filter

A commercial version of the Biosands FilterPatented in 1993, the Davnor BioSand Water Filter is an innovative system that creates safe drinking water for millions of people around the world using 170-year-old technology. Slow sand filtration is a low-tech process that has only recently been modified to meet the needs of consumers and developing nations.

The basic device consists of a large container filled with sand and gravel. As water passes through the various layers, foreign particles and organisms are filtered out and the end product is relatively safe drinking water.

Cross-section of the Biosands Concrete Water FilterThough simple to use, slow sand filtration has not met widespread success; it requires a continuous source of water and, at best, will only remove 60 percent of pathogens. Alberta inventor Dr. David Manz kept this in mind when developing the BioSand water filter, a commercially successful invention that has proved invaluable in third world countries. Modifications to the classic filter system include a diffuser, which is fitted over the opening of the basin to distribute the water gently over the top layer of sand. This method reduces the level of disturbance to the most important part of the filter, the biolayer.

Biosands Water FilterThe biolayer is formed with the accumulation of organic material in the first layer of sand. Oxygen and nutrients are delivered through a small reserve of water that remains on top of the filter, a feature that distinguishes the BioSand filter from similar devices. The microorganisms that make up most of the biolayer consume bacteria, increasing the effectiveness of the filter and eliminating 90 percent of pathogens. The sand absorbs viruses, iron and other small particles.

The BioSand filter runs on a demand basis and requires no electricity or chemicals, making it ideal for communities with few resources. The technology is applied to both the commercial version, which Dr. Manz’s company Davnor sells, and the concrete version, which is manufactured and installed in developing countries.

Click here for more information on the Centre for Affordable Water and Sanitation Technology.

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