Olives pour oil on troubled waters

Scientists from the University of Grenada’s Department of Chemical Engineering have discovered a process by which olive stones can be used to remove chromium from industrial wastewater.

The process is based on biosorption, the property of certain types of biomass to retain pollutants. It can be used to purify water from paint, tannery or galvanising industries, among others.

After olive oil is produced, agricultural residues remain, such as olive vegetable water, leaves, and the solid waste known as ‘alperujo’. A study carried out by Dr Germán Tenorio Rivas, a member of the Solids Concentration and Bioremediation Research Group at Grenada, found that olive stones eliminate hard metals, including chromium, from sewage water by biosorption.

The process of biosorption of chromium by olive stones stems from their capacity to retain metallic ions in their surface.

‘This is due to the difference in electrical charges,’ said Rivas. ‘Olive stones are negatively charged, whereas metal is positively charged. That is the reason why they come together, thanks to ionic attraction.’

The process of biosorption represents a substitute for other processes such as precipitation which are far more complex and expensive.

‘Unlike these processes, the use of olive stones as a biosorption mechanism produces no sub-products which are then difficult to deal with, for instance, metal infused mud,’ said Rivas.

The products of this process are purified water and the olive stones with the retained metal, which can be extracted and used later. The olive stones can also be used as biomass for energy production.