Cactus extract can purify contaminated water: study

Washington: The inner "guts" or mucilage of commonly found cacti can effectively purify contaminated drinking water, clean recirculating aquarium water and even mop up oil spills in oceans, scientists have found.

The technology makes use of century-old knowledge that mucilage from some common cacti can clean drinking water.

Using boiled prickly pear cactus to capture particles in sediment-laced dirty water makes the sediments sink, and the water at the top of the bucket becomes clear and drinkable, researchers said.

"We found there is an attraction between the mucilage of cactus and arsenic," said Norma Alcantar, from the University of South Florida (USF) in US.

"The mucilage also attracts sediments, bacteria and other contaminants. It captures these substances and forms a large mass or 'floc' that sort of looks like cotton candy," Alcantar said.

"For sediments, the flocs are large and heavy, which precipitate rapidly after the interaction with mucilage," she said.

Researchers tried the approach to clean contaminated drinking water and found it worked well.

Common worldwide, cacti are a sustainable product and are not only nontoxic, but are edible and considered a delicacy.

Cactus mucilage was found to be an effective oil dispersant, and could be used to clean up oil spills from seawater, researchers said.

The researchers found that cactus extract could clean recirculating aquarium water, as well as water in aquaculture tanks and ponds.

Such tanks create conditions that encourage bacterial growth that in turn develops unpleasant smelly compounds, such as 2-methylisoborneol (known as MIB) and geosmin, researchers said.

These compounds result in the musty, earthy flavour that is sometimes in the water and the fish that live in it.

At harvest, the current practice is to purge the fish and tanks with fresh water, which takes months, uses large amounts of water and stresses the fish, Alcantar said.

The researchers are currently studying the chemical composition of the mucilage, which is made up of carbohydrates and some 60 sugars, with the goal of synthesising it in a lab.

They are developing a prototype of a recirculating aquaculture system that uses cactus extract as a cleansing agent and they will conduct a life cycle analysis of the system.