Jean Engineering

Podcast

Jean Engineering

Transcript

Arsenic and old jeans? I'm Bob Hirshon and this is Science Update.

Four hundred years of lead, silver and zinc mining has left the city of Zimapán, Mexico surrounded by piles of toxic soil. The dirt contains arsenic that contaminates the drinking water.

Geology major Katherine Heggeman, a senior at Bates College in Lewiston, Maine, is part of a team of scientists trying to clean up the water. Heggeman’s group found that crushed limestone could absorb the arsenic. But she says filtering out the tainted limestone was a problem. She tried coffee filters, t-shirt fabric and other material, and none of them worked.

Heggemen:
So then, I was, I was totally at a loss. I has no idea what to do, and somebody who was working with me said, “Gee. Why don’t we try blue jeans?” They’re more tightly woven than t-shirts, and they don’t seem to be as porous as coffee filters. So we tried two layers of denim and, you know, there it was. There was water that was clear, and I tasted the water and it tasted fine to me.

She says the method is simple and inexpensive, so residents can start using it right away.

Heggemen:
This is just for personal use, using materials that everybody has.

And while large-scale water treatment is in the works, for now most of the residents will have to rely on Heggeman’s limestone and denim treatment for water that’s safe enough to drink.

For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

This Science Update illustrated the fact that engineering projects need not be high-tech in order to be effective. The Internet resources provided below in the Going Further section offer many examples of the power of everyday materials and ingenuity in resolving environmental and agricultural challenges. As a follow up to this lesson, you may want to look for small-scale, low-tech solutions to environmental problems within your own community.

Now try to answer the following questions:

1. What caused the water contamination in Zimapán?
2. Describe the filtration system devised by this group of researchers.
3. What role did the denim play in this filtration system? Why denim? Can you think of other materials that might work as well?
4. Are there any additional environmental risks caused by this filtration system? If so, do the benefits of using this system outweigh the risks? Why or why not?
5. What are the benefits of using this low-tech remediation technique? What are the drawbacks? Would this technique by realistic as a long term solution? Why or why not?
6. Visit What is "activated charcoal" and why is it used in water filters? from How Stuff Works. How similar is Zimapán's filtration process to activated carbon filtration?

Going Further

To investigate ways in which low-tech solutions are being used throughout the world, go to Photofile from the Food and Agriculture Organization of the United Nations. Scroll down to the Archives section for photos and brief paragraphs on low-tech engineering solutions being used to combat world hunger. Particularly relevant are the sections on Desertification, Post-Harvest Technology, Improved Cookstoves, and Small-Scale Irrigation. Read the brief case study entitled A modest grater means safer and quicker cassava in Uganda for a powerful example of a small-scale improvement leading to large-scale results.

Visit Selenium: A Window on Wetlands: How Do Contaminants Move and Change in an Ecosystem? from the Microworlds website. This lesson puts students in the role of researcher as they investigate the link between a decline in waterfowl in California and the element Selenium (Se). How did the Se get there and what can we do to protect wildlife from contamination? Students use a series of clues to find out how scientists studied this problem and what answers they found.