Cactus to Purify Water

Not just for storing water. Photo courtesy: Philip Condit II/Stone/Getty

Science has made a new discovery with regards to the prickly pear cactus. While cactus have long been a known source of water for those lost in the desert, it has not been officially recognized until now that an extract from the prickly pear is effective at removing sediment and bacteria from dirty water.

Many water purification methods introduced into the developing world are quickly abandoned as people don't know how to use and maintain them, says Norma Alcantar at the University of South Florida in Tampa. There is also the costs associated with these methods - many communities can't afford to maintain the equipment properly; and, it eventually fails.

Ms. Alcantar and her colleagues decided to investigate the viability of using an old (19th Century) Mexican method of purifying their water. They used the thick, gel stored in the leaves of the prickly pear cactus, Opuntia ficus-indica. This cactus is found globally.

The cactus uses the mucilage - the thick gum in the middle of the leaves - to store water. The team extracted the mucilage and mixed it with water to which they had added high levels of either sediment or the bacterium Bacillus cereus.

Alcantar found that the mucilage caused the sediment particles to join together and settle to the bottom of the water samples. The gum also caused the bacteria to combine and settle allowing 98% of bacteria to be filtered from the water (Environmental Science and Technology, DOI: 10.1021/es9030744). They now intend to test it on natural water.

Householders in the developing world would only have to boil a slice of cactus to release the mucilage and add it to water in need of purification, says Alcantar. "The cactus's prevalence, affordability and cultural acceptance make it an attractive natural material for water purification technologies."

While many are looking at this as a possible breakthrough in the ever growing crisis over the availability of ample, clean drinking water, Colin Horwitz of GreenOx Catalysts in Pittsburgh, Pennsylvania, says many issues remain. He points to the question of how much land and water will be needed to grow cacti for widespread water purification; and, wonders how households will know when and if all the bacteria have been removed.

Via NewScientist