What type of soil filters water best?

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Clarification of Question by mangodango-ga on 12 Jan 2005 16:28 PST

Soil is defined as the outer covering of the earth where plants grow.
We know that soil has at least one of three minerals, silt, sand and
clay, along with air, water, and organic matter. If we tested 4-5
different types of soil which would filter water best? Where would you
find these soils? How would you test?

Have a look at:

http://www.uwsp.edu/water/portage/undrstnd/soil4.htm
and
http://ltpwww.gsfc.nasa.gov/globe/filter/filter.htm

Generally, clay-rich soils with a reasonable amount of organic matter
(sufficient to support microbial activity) should act as the "best"
filters", but this will depend, to some extent, on what specific
things one wants to remove from the water.

Here's an interesting cheap water filter.

http://info.anu.edu.au/mac/Media/_pdf/ClayPotFilter_final_web.pdf
http://www.abc.net.au/catalyst/stories/s1381331.htm

"A handful of clay, yesterday?s coffee grounds and some cow manure the
ingredients that could bring clean,safe drinking water to much of the
third world.  The simple new technology,developed by ANU materials
scientist Mr Tony Flynn,allows water filters to be made from commonly
available materials and fired on the ground using cow manure as the
source of heat, without the need for a kiln.The filters have been
tested and shown to remove common pathogens including E-coli.

Unlike other water filtering devices,the filters are simple and
inexpensive to make."