A team of researchers led by Stephan Kohler of the Graz University of Technology in Austria have completed tests showing that sea shells can remove heavy metal pollution from water.

The researchers have cleansed water in Vietnam’s Saigon River, which was tainted with toxic metals like cadmium, zinc, lead and iron from factories on the outskirts of Ho Chi Minh City, using nothing but sea shells  Being able to combat water pollution with such a cheap material could save millions of lives in coastal cities throughout the developing world.

Kohler’s team has found that crushed clam or mussel shells, which are made of aragonite (a form of calcium carbonate),  readily swap out calcium atoms in favour of heavy metals, locking them into a solid form.

The effect ceases, and the shells start leeching out the metals, if the water becomes acidic – but, because the shells are naturally basic, all you have to do to reverse the leeching out is to add more shells.

While developed  countries, which can afford them, use more sophisticated filtration techniques, coastal communities in the developing world could greatly reduce the public health risk posed by toxic heavy metals in their water supplies using shells like cockle, mussel and clam which are available in large quantities as a waste product of the seafood industry.

Seashells (public domain)
Seashells (public domain)