South Australia’s Great Artesian Basin, known for the diverse endemic invertebrate fauna living in the springs along the margins of the basin, is not immune to the water challenges that mining in the region represents. The distribution of the salt pipewort (Eriocaulon carsonii) is restricted to the habitats provided by the springs. The persistence of the aquatic invertebrates and the salt pipewort is linked to the availability of free-flowing water; changes in spring flow and wetland area can affect these populations.
BHP Billiton pumps water from the basin to its Olympic Dam copper/uranium mining operations some 110 kilometers north and 200 kilometers north-east. In order to ease its impacts on this area, the company has developed a project to reduce water consumption by optimizing water recovery and recycling and substituting poor-quality local groundwater in some areas.
Over 90% of the Olympic Dam site’s water consumption occurs in three main processing areas: the concentrator (where minerals are “concentrated” into one area, usually by flotation, for extraction), hydromet (a mineral processing technology that uses water-based solutions of chemicals to dissolve valuable metals from their ores or concentrates or intermediate products) and smelter plants. Further processing of the basin’s water is carried out at the on-site desalination plant to produce a potable water supply for both the mine site and nearby Roxby Downs and Andamooka townships.
BHP Billiton recognizes that the responsible use of water is essential to protecting the environmental values of the springs, a key concern for stakeholders. Thus the company monitors the rate at which it extracts water from the two well fields to ensure that it is always within prescribed limits and that adverse impacts are not occurring. The company’s ongoing challenge is to continue to meet these limits while optimizing plant production rates.
Key to meeting this challenge is improving water use efficiency. To do this, the company created a dedicated team to assess:
- Current industrial water use volumes and purposes
- Particular process streams and plant areas with substantial increases in production-based water consumption
- The potential for reductions through increases in efficiency, recycling and reuse of process streams.
- A series of water use maps, including numerical balances and comparisons of both current and historical data, was created for the concentrator, hydromet and smelter plant areas. Water savings projects were then identified through discussions of water map data with area personnel or suggestions from area personnel.
The project confirmed the importance of regular inspection, testing and calibration of process indicators.
Significant water savings have been identified and implemented in the three key production areas:
- 1.6 megaliters (ML) per day savings (or 70% of demand) in the slag milling circuit due to a collaborative project implemented by the Water Savings Initiative team and the concentrator metallurgists
- 0.5 ML/day savings (or 50% of demand) in the concentrate filtration plant following a suggestion by an area technician.
1.2 ML/day savings (or 55% of demand) in the counter-current decantation area due to a procedural review and re-education program. Further opportunities for this area are under investigation, including control systems review and further recycling options.
0.3 ML/day savings (or 65% of demand) in the electric furnace gas scrubbing system due to improved operation of the control valve. Further opportunities to reuse the remaining gas scrubber wastewater in other process areas are under review.
Other savings – totaling 2.9ML/day have been achieved or are planned in other sub-areas of the plant.
Further water saving initiatives are anticipated from the following ongoing activities:
- The identification and reclamation of reusable or recyclable process streams
- The identification of “leadingpractice” use of water for individual plant areas
- Future changes to the operations based on the requirement to maintain or increase water efficiency.