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USF scientist filtering water with cacti

The Tampa Tribune
Published:   |   Updated: March 21, 2013 at 09:17 PM
TAMPA -

Norma Alcantar was never content with the simple facts.

When her high school science teacher in Mexico told her everything was made of minuscule objects called atoms, she wanted to know what that meant. What did the atoms look like? What did they do?

And when her grandmother told her about using cactus to purify water when she lived on a farm as a girl, Alcantar wanted to know more. How did it work? Could anybody do it?

Alcantar grew up, went to college, then graduate school in California. Today, at 39, she has a Ph.D. and a lab at the University of South Florida that's turning her grandmother's folk ways into science.

One day, she hopes, people around the world will be able to use that science to purify polluted water.

"I think that's why I went into chemistry and chemical engineering," Alcantar said. "So I could figure out all these things I didn't know about."

Alcantar has presented papers and published half a dozen journal articles on findings by her and her students.

In June, she received a $100,000 grant from the National Science Foundation to study how the Haiti earthquake disrupted water supplies and whether the cactus treatment could have been used to clean the polluted water.

Earlier this month she visited Vietnam to talk about her technique.

"It's really a very easy process," Alcantar said from her New Tampa home, where the back patio is lined with prickly pear cactus plants.

The prickly pear cactus grows almost anywhere, even as far north as Canada.

Many people around the world are already using cactus plants, seeds and other natural "flocculants" to clean their water, said Daniele Lantagne, an environmental engineer with the Centers for Disease Control and Prevention. They can remove harmful bacteria and chemicals and they're inexpensive, he said.

Alcantar hopes to develop a process that anyone could use.

"We want to have this technique available for low-income communities everywhere, to give them drinking water that is safe," she said.

One advantage of Alcantar's research is that it uses a natural material, said John Wiencek, USF College of Engineering dean, who met Alcantar before he came to USF, when she demonstrated her work several years ago at the University of Iowa.

"This is more appealing to people, especially from emerging countries where they may be skeptical of technology," Wiencek said.

Many USF engineering researchers, from bridge builders to people who study cooking methods, work to develop techniques acceptable to people of other cultures, Wiencek said.

Alcantar starts with the slimy stuff inside the prickly pear cactus. It's called mucilage, and it's the substance that enables the plant to store water in the desert.

Across Mexico, where Alcantar grew up, people eat the prickly pear. They boil or saute it with eggs, steak, onions, anything, Alcantar said.

But when her grandmother was growing up, after her relatives boiled the cactus, they had an additional use for the water.

If there had been a lot of rain, and the water supply was muddy, they'd put the cactus water and the muddy water together. After a bit, the sediments would clump together and settle, leaving clean water on the top.

"It's like a fishing net that collects whatever is in the water," Alcantar said. "The plant actually creates a structure. We've seen it at the microscopic level."

If it worked with sediments, Norma thought, how about bacteria? It did.

And heavy metals, such as arsenic? That worked, too, though she discovered that the chemical reaction was a little different. When the metals contacted the mucilage, they rose to the top of the water, where they could be scooped and filtered away.

What's happening, Alcantar has learned, is the sugars in the mucilage are binding to the foreign substances in the water, turning them into removable clumps.

It doesn't take a lot of cactus, she said. One piece, or pad, of prickly pear would probably last several weeks.

People can create their own mucilage by boiling down the cactus. But she also has developed a way to turn it into a powder, which can be mixed with water to create different mucilage concentrations.

That's important in adapting the practice to countries because water qualities vary from one to another, she said. Some may need a strong solution, some may not.

Alcantar has applied for a patent on this process. This would keep a private company from coming behind her, getting its own patent and setting a price that a low-income community couldn't afford, Wiencek said.

Alcantar isn't finished with her research.

She already knows the cactus goo works with sediments, bacteria and arsenic, but it could also work with other heavy metals, bioterrorism compounds, even oil, she said.

And this isn't her only project.

She's working with cancer and Alzheimer's researchers on developing tiny biological containers to carry drugs to targeted areas of the body.

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