The average longwall mine can use between one and two megalitres each day, and particularly in rural New South Wales mines are increasingly finding themselves in competition with landholders, farmers and communities over rights to available water.
Horn said nowadays when a mine takes supplies that would otherwise flow into rivers feeding farmlands or a potable supply from the local council, its water use is being reviewed in terms of the other community and industrial demands on that water.
He said many states are also campaigning for lower salinity discharges to meet the ANZECC 2000 freshwater emissions standards for mine waters released into surface river systems.
“This is increasingly driving expanding mine operations to implement sophisticated mine water treatment technologies to ‘drought proof’ remote operations to ensure long-term viability,” Horn said.
Both industrial and natural mine water re-use technologies have been developed and can run in conjunction with each other to allow a better managed and sustainable outcome for mining operations.
While the natural systems have a high upfront cost, Horn said they attract lower long-term costs and create community benefits from improved run-off water quality and visual impacts, compared to a constructed industrial plant.
HLA-Envirosciences has been involved with the evaluation of the water filtration plant for Illawarra Coal’s Douglas Project, which will require 1.1ML to run its longwall once operating – which can be recycled water but needs to be close to potable quality, high-quality recycled industrial water.
In terms of which treatment technologies are suitable for individual mines, Horn said each water source is unique, and a combination of systems is often used to achieve the best outcome.
Illawarra Coal said construction of the $6 million water filtration plant at Douglas will enable the mine to treat and re-use more than 2ML of mine water every day – equivalent to two Olympic-size swimming pools.
The water will be used in a number of the site’s operating areas and processes as well as at other nearby mines.
The project was approved in mid-2006 following onsite trials conducted from November 2005 to February 2006 which tested three different types of filtration plants.
During that period, the company monitored the three plants’ energy usage, mine water input, clean water output, treatment chemical usage and by-products produced. The trial plants used reverse osmosis technology.
Illawarra Coal general manager of sustainable development Wendy Tyrrell said the environmental and social benefits from installing the water filtration plant will be significant.
“The plant will enable us to convert low level saline underground water to fresh water which can be re-used onsite, as well as at other nearby mines. This will reduce the amount of fresh water used from the Sydney Water supply, which not only saves us money but conserves water as well,” she said.
“It will also improve the quality of our discharges from the mine which, ultimately, flow into the Nepean River.”
The Douglas water filtration plant is expected to be operational by December 2006.