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Cactus Water Filter

March 24, 2016

The drought-defying interior of the prickly pear cactus holds a secret to purifying water.



The interior of a prickly pear, or nopal cactus, binds to contaminants in water. (Susanne Bard)


Cleaning with cactus. I’m Bob Hirshon and this is Science Update.

In Mexico, boiled prickly pear cactus is a popular dish. When University of South Florida chemist Norma Alcantar was a teenager, her Mexican grandmother recounted how the leftover cactus pulp was used to clean up buckets of dirty water to make it safe for drinking. 

NORMA ALCANTAR (University of South Florida):

Later when I became a professor I started actually doing some experimentations with the cactus.


Alcantar’s lab has found that carbohydrates in the pulp bind to contaminants like arsenic and bacteria, making them heavier so they settle out. At the meeting of the American Chemical Society she reported that it even removes foul odors from ponds. She says powdered cactus could be a cost-effective way for low-income rural communities to treat their water.


They can learn how to extract it and then they can apply it to dirty water just like my grandma was using it when she was little.


I’m Bob Hirshon, for AAAS, the Science society.