1. Simple Way to Remove Mud from "The water has a lower sodium concentration
Drinking Water than Gatorade," Pearce says. This would still be
too much salt to pass muster as American tap
NAME _____________ Date_____ Per__ water, but American tap water is not the
alternative.
Leaving bottles of water in the sun kills "I've drunk this water myself. If I were
pathogens--but only if the water is transparent. somewhere with no clean water and had kids
Michigan Tech's Joshua Pearce has devised a with diarrhea, and this could save their lives, I'd
simple way to clarify water, so even muddy use this, no question," he says.
water could be made safe for drinking. (Credit:
SODIS Eawag photo) Salt works best when the suspended particles are
a type of clay called bentonite. The technique
ScienceDaily (May 1, 2012) — Nearly 80 doesn't work as well with other kinds of clay.
percent of disease in developing countries is However, by adding a little bentonite with the
linked to bad water and sanitation. Now a salt to water containing these different clays,
scientist at Michigan Technological University most of the particles glom together and settle
has developed a simple, cheap way to make out, creating water clear enough for SODIS
water safe to drink, even if it's muddy. treatment.
It's easy enough to purify clear water. The solar Pearce and Dawney are running more tests on
water disinfection method, or SODIS, calls for water containing various types of clays, and they
leaving a transparent plastic bottle of clear water are also investigating different soil types across
out in the sun for six hours. That allows heat and Africa to see where their methods might work
ultraviolet radiation to wipe out most pathogens the best.
that cause diarrhea, a malady that kills 4,000
children a day in Africa. Review Questions Cornell
It's a different story if the water is murky, as it 1. On what date was the article written?
often is where people must fetch water from 2. Nearly 80% of disease in developing
rivers, streams and boreholes. "In the developing countries is linked to what factor?
world, many people don't have access to clear
3. What does the water purification method
water, and it's very hard to get rid of the
of SODIS calls for?
suspended clay particles," says Joshua Pearce,
an associate professor of materials science and 4. What does the heat and ultraviolet
engineering. "But if you don't, SODIS doesn't radiation do to the water?
work. The microorganisms hide under the clay
and avoid the UV." 5. What do microorganisms do in muddy
(clay) water?
Thus, to purify your water, you first have to get
the clay to settle out, a process called 6. What is the name of the process that
flocculation. Working with student Brittney causes clay to settle out of the water?
Dawney of Queen's University in Ontario,
Pearce discovered that one of the most abundant 7. What mineral is used in this process?
minerals on Earth does this job very well: 8. What happens when salt combines with
sodium chloride, or simple table salt. benotite?
Salt is inexpensive and available almost 9. What happens to the water for the
everywhere. And it doesn't take very much to SODIS treatment?
make muddy water clear again.
2. 10. What did Pearce and Dawney want to
investigate?
