Shortage of water in open-cast mining calls for new solutions
• Siemens technologies ensure multiple reuse for production
August 3, 2007 -- More and more often now, water shortages are jeopardizing open-cast mining operations, and despite rising demand for raw materials the mining companies are unable to raise production further.
"Not only that, there is also the fact that wastewater contaminated with heavy metals, arsenic, chlorides and sulfates can no longer be used for production," explains Dr. Markus Vöge, responsible for global mining business at Siemens Industrial Solutions and Services (I&S).
"At the same time, though, ever tighter environmental regulations mean the wastewater can't be discharged." Siemens provides water treatment systems that are geared to the pollutant mix at a particular open-cast mine; they remove pollutants from the water cycle and return fresh water to be reused in production. This enables open-cast mining enterprises to secure production, expand their capacity and significantly reduce the burden on the environment.
Open-cast mines need as much as 70,000 cubic meters of water per day to keep production running smoothly. This is equivalent to the water requirements of a large city. Up to eight tonnes of water are used per tonne of ore. Although water consumption in the open-cast mining sector has declined by an average of 60 per cent since 1990, the situation as a whole has deteriorated because of the growth in production. In Latin America in particular, open-cast mines are no longer able to exploit their full production capacity as they no longer have sufficient fresh water available to process the ores.
The system used to treat water that has been contaminated with heavy metals and sulfates in the flotation process, for example, is the ARD/AMD (acid rock/mine drainage) system from Siemens I&S. This system is a combination of conventional chemical treatment processes and membrane technology. A chemical process removes the suspended material and the membranes remove the toxic substances. Thanks to this combination, only little sludge waste is generated and fewer chemicals are needed than with conventional systems. Running costs are therefore lower, and the companies are able to comply with tough environmental directives. Membrane technology is used to treat the water from the tailings dam, removing 99 per cent of the toxic material from the water. Remaining particles are filtered out in a clarifying basin. No additional chemicals are needed for this process. The filter system cleans itself at periodic intervals.
The treated water from the flotation process and the tailings dam can be returned to the process cycle. "Today we are able to treat as much as 80 per cent of the contaminated water and put it back into the production cycle," stressed Dr. Vöge. There are solutions suitable for all sorts of different open-cast mines as the systems could be combined on a case-by-case basis. The flexible design allows the treatment of volumes of water ranging from a few hundred to thousands of cubic meters. With the highest possible rate of recovery by the integrated membrane systems, up to 99 per cent of the pollutants can be removed from the wastewater.
Further information at: http://www.siemens.com/mining
The Siemens Industrial Solutions and Services Group (I&S) is the integrator of systems and solutions for industrial and infrastructure facilities and global service provider for the plant and projects business covering planning, installation, operation and the entire life cycle. I&S uses its own products and systems and process technologies in order to enhance productivity and improve competitiveness of companies in the sectors of metallurgy, water treatment, pulp and paper, oil and gas, marine engineering, open-cast mining, airport logistics, postal automation, intelligent traffic systems and industrial services. In fiscal 2006 (to September 30) I&S employed a total of 36,200 people worldwide and achieved total sales of EUR 8.819 billion, according to U.S. GAAP.
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