SCOTT SIMON, HOST:

A cactus doesn't need much water to live. But the quality of water can be considerably improved if you throw some cactus into it. Or precisely, the gooey stuff inside a cactus can act like a filter that purifies water that's contaminated with heavy metals or bacteria. This cleansing property of cacti is the focus of Norma Alcantar's research. She teaches chemical and biomedical engineering at the University of South Florida and joins us from the studios of WUSF. Thanks so much for being with us.

NORMA ALCANTAR: Yes. Thank you, Scott, for the invitation.

SIMON: So practically, if you come across some contaminated water (laughter), you have to be conveniently in a desert with cacti, though, right?

ALCANTAR: We have a technique where we extract the gooey part of the cactus, and we make it in a powder form. And then you can add this powder to water to separate the water.

SIMON: Yeah. So I gather you've done work in Haiti following the earthquake, for example, and after the BP oil spill.

ALCANTAR: Yes. Our work in Haiti centered on looking at heavy metals and bacteria after the area where there were a higher number of metals that actually went into the groundwater. So we found an interaction with the cactus to be able to be used in an emergency response fashion.

SIMON: What put the idea in your mind that maybe cacti could be used this way?

ALCANTAR: Well, it's a very good story (laughter) because it actually involves my grandmother. She grew up in the in early 1900s in rural Mexico.

And one time when I came to visit her after high school, she asked me about my day. And I told her that I had chemistry lab that day, and we were working with this substance. There are surfactants that usually you find in soaps and detergents. And they're use to clean dirty dishes and dirty water. And she knew all about it.

So I say - oh, why did you know about this? She's, like, well, you know, when I was little, I used to bring water from the retention pond or the river, depending on the season. And the water will contain some contaminants - some sediments and debris. So at that time, they will actually cook the cactus and use part of the water that they obtain after cooking it to clean water. You know, the rest is history.

SIMON: So your grandmother growing up in rural Mexico in the early part of the 20th century (laughter) knew something that you wind up developing and that's helping people around the world.

ALCANTAR: Yes. That was very special for me. And she died in 2008. But I was able to tell her after we received our first grant from the National Science Foundation that we were doing studies and that it really worked. You know, she told me that she knew that it was going to work.

(LAUGHTER)

SIMON: Yeah, what do you mean? Yeah, of course, I knew that.

ALCANTAR: Right.

SIMON: Norma Alcantar is a professor at the University of South Florida. Thanks very much for being with us.

ALCANTAR: Thank you. Transcript provided by NPR, Copyright NPR.