It’s easy enough to purify clear water. The solar water disinfection method, or SODIS, calls for leaving a transparent plastic bottle of clear water out in the sun for six hours. That allows heat and ultraviolet radiation to wipe out most pathogens that cause diarrhea, a malady that kills 4,000 children a day in Africa.
It’s a different story if the water is murky, as it often is where people must fetch water from rivers, streams and boreholes. “In the developing world, many people don’t have access to clear water, and it’s very hard to get rid of the suspended clay particles,” says Joshua Pearce, an associate professor of materials science and engineering. “But if you don’t, SODIS doesn’t work. The microorganisms hide under the clay and avoid the UV.”
Thus, to purify your water, you first have to get the clay to settle out, a process called flocculation. Working with student Brittney Dawney of Queen’s University in Ontario, Pearce discovered that one of the most abundant minerals on Earth does this job very well: sodium chloride, or simple table salt.
Salt is inexpensive and available almost everywhere. And it doesn’t take very much to make muddy water clear again.
“The water has a lower sodium concentration than Gatorade,” Pearce says. This would still be too much salt to pass muster as American tap water, but American tap water is not the alternative.
“I’ve drunk this water myself. If I were somewhere with no clean water and had kids with diarrhea, and this could save their lives, I’d use this, no question,” he says.
Salt works best when the suspended particles are a type of clay called bentonite. The technique doesn’t work as well with other kinds of clay. However, by adding a little bentonite with the salt to water containing these different clays, most of the particles glom together and settle out, creating water clear enough for SODIS treatment.
Pearce and Dawney are running more tests on water containing various types of clays, and they are also investigating different soil types across Africa to see where their methods might work the best.
Their paper “Optimizing the Solar Water Disinfection (SODIS) Method by Decreasing Turbidity with NaCl” has been accepted for publication in the Journal of Water, Sanitation, and Hygiene for Development and will appear in June. A preprint of the paper is available here.
Michigan Technological University (www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.
Joshua Pearce | EurekAlert!
Scientists discover the basics of how pressure-sensing Piezo proteins work
22.08.2019 | Weill Cornell Medicine
Protein-transport discovery may help define new strategies for treating eye disease
22.08.2019 | Scripps Research Institute
Since their experimental discovery, magnetic skyrmions - tiny magnetic knots - have moved into the focus of research. Scientists from Hamburg and Kiel have now been able to show that individual magnetic skyrmions with a diameter of only a few nanometres can be stabilised in magnetic metal films even without an external magnetic field. They report on their discovery in the journal Nature Communications.
The existence of magnetic skyrmions as particle-like objects was predicted 30 years ago by theoretical physicists, but could only be proven experimentally in...
Theoretical physicists at Trinity College Dublin are among an international collaboration that has built the world's smallest engine - which, as a single calcium ion, is approximately ten billion times smaller than a car engine.
Work performed by Professor John Goold's QuSys group in Trinity's School of Physics describes the science behind this tiny motor.
Together with the University of Innsbruck, the ETH Zurich and Interactive Fully Electrical Vehicles SRL, Infineon Austria is researching specific questions on the commercial use of quantum computers. With new innovations in design and manufacturing, the partners from universities and industry want to develop affordable components for quantum computers.
Ion traps have proven to be a very successful technology for the control and manipulation of quantum particles. Today, they form the heart of the first...
Experimental progress towards engineering quantized gauge fields coupled to ultracold matter promises a versatile platform to tackle problems ranging from condensed-matter to high-energy physics
The interaction between fields and matter is a recurring theme throughout physics. Classical cases such as the trajectories of one celestial body moving in the...
Soft robots have a distinct advantage over their rigid forebears: they can adapt to complex environments, handle fragile objects and interact safely with humans. Made from silicone, rubber or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.
Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines' moving parts. Because they are connected to these bulky pumps by tubes,...
16.08.2019 | Event News
14.08.2019 | Event News
12.08.2019 | Event News
23.08.2019 | Medical Engineering
23.08.2019 | Power and Electrical Engineering
23.08.2019 | Life Sciences