FEATURE-Evaporating water supply poses costly risk for miners

Thu May 30, 2013 6:59am EDT
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By Julie Gordon

MINA ZALDIVAR, Chile May 30 (Reuters) - High in Chile's bone-dry Atacama desert, mining engineer Enrique Miranda surveys a metal structure filled with a pungent mix of earthworms and woodchips. Sprinklers inside the enclosure snap to life, shooting waste water from the nearby mining camp into the wriggling mass, which serves as a natural filter.

"That's lunch for the worms," says Miranda, an environmental supervisor who has worked at Barrick Gold Corp's Zaldivar copper mine for 18 years.

The worms munch through all the waste water generated each day at the mine's camp and office facilities (not from the mine itself) and eventually produce irrigation quality water. The experimental process forms part of Barrick's efforts to get more than 90 percent of Zaldivar's annual water needs from recycling. The mine also reuses much of the water used in the extraction process, reducing the amount of new fresh water needed.

The recycling plant highlights the lengths that miners like Barrick, BHP Billiton Ltd and Antofagasta Plc have to go to assure adequate supplies of water for everything from toilets for their workers to separating the valuable metals in the ore body from waste rock and tamping down dust that heavy trucks kick up.

"I link the need to have water with the urgency of having an ore body," said Bill Williams, Barrick's vice president for environmental issues, referring to the mineral deposit. "If you don't have the water to produce the ore body, you don't have anything. It's critical for most mining ventures - certainly for the ones we're involved in."

Traditionally, water has come from rivers or underground, but many sources are running dry, crippling production and delaying developments of mines around the world. Shortages have pitted mining companies against farmers and others who fear for the quality and quantity of their supplies.

Miners have been forced to turn to more expensive options like seawater desalination and sewage treatment plants to obtain water for their needs and for the communities around them.   Continued...