The mining industry in Australia is projected to grow over the next decade. With this expansion in production, a similar increase in water use will be seen. In Western Australia alone, this increase in water use is predicted to top 97,000,000,000 L/year. Each mineral sector has its own challenges relating to securing water supplies. Increasingly in the mining of metal ores, with the exception of iron ore, alternative sources of water such as treated saline groundwater or water recycled from mine operations are being used to secure water supplies.
Iron ore
Iron ore, of which Australia has the largest reserves in the world, represents almost half of Australia’s mineral export earnings. It is estimated that between 2000 L and 5000 L of water is required to produce a tonne of iron ore. 94% of Australia’s iron ore reserves are in Western Australia with Western Australia responsible for 99% of the production of iron ore in Australia. The bulk of the iron ore mines in Western Australia are located in the Pilbara region which is an arid region that regularly experiences temperatures in excess of 45 degrees Celsius. Almost all mines in the Pilbara are supplied with low salinity groundwater which is recharged annually during summer rains and cyclone events. However, 40% of mining operations in the Pilbara are projected to be below the water table by 2040, requiring large scale dewatering efforts. At least 50% of the extracted water will be returned to groundwater via reinjection bores to minimise the effect on the water table of mining operations.
Black coal
Coal, particularly black coal, is Australia’s second largest mineral export by revenue (at around 30%). Australia is also the largest black coal exporter in the world, exporting around 70% of the total volume mined. The major producer of black coal is Queensland although 36% of black coal is produced in NSW. Coal mining requires around 650 L of water for every tonne of coal produced, making securing water supplies essential. The two largest black coal reserves in Australia are the Bowen basin in Queensland and the Sydney basin in NSW. Mines in the Bowen and Sydney basin are both fed by groundwater aquifers however there is concern that mining activities in these basins may contaminate nearby water resources. The Bowen basin, particularly the mines in the southern section, overlies the Great Artesian Basin which is one of the largest freshwater resources in the world and is an essential resource for 180,000 people. Each mine is required to carefully monitor its groundwater extraction to determine if it is contaminating the overlying basin. In 2014 a review funded by the Australian Department of Environment (which included researchers from CSIRO, private industry and universities) determined that there was still insufficient evidence available to determine if these two basins were connected and if contamination of the Great Artesian Basin was occuring.
Gold
Gold, which represents 10 % of Australia’s mineral export revenue, is predominantly mined in Western Australia which has 11 of the 14 largest gold mines in the world and accounts for 70% of Australia’s production. Further development of gold mining in Western Australia’s Goldfield region is being hindered by access to water. Gold is a water intensive mineral to mine and process, taking 250,000,000 L of water to produce a tonne of gold. The Goldfields region of Western Australia is semi-arid and the groundwater is saline. Currently the region is fed by the 556 km “Golden Pipeline” which connects the Mundaring Weir east of Perth to Kalgoorlie-Boulder in the Goldfields. The pipelines can pump up to 90 million litres a day but this is insufficient due to the water volumes required for gold mining. Groundwater treatment, particularly using Reverse Osmosis, would allow for water to be produced locally from the saline groundwater and allow for additional gold mines to open in this region.
Zinc
Zinc represents 1.6% of Australia’s mineral export earnings and Australia is the third largest zinc producer in the world with significant mines at Mount Isa, Dugald River and Lawn Hill (all in Queensland), McArthur River (in Northern Territory) and Yalgoo (in Western Australia). Different zinc mines are faced with different water issues. Mount Isa Mines draw water from the Moondarra Dam (Lake Moondarra) and are allocated 47.5% of the total catchment. This catchment is currently at risk of flooding due to recent heavy rainfall. In contrast, the Golden Grove Mine in Western Australia is unable to rely on surface water and instead treats saline groundwater using a combination of oxidation/filtration (to remove heavy metals) and reverse osmosis (to reduce the salinity). The combined water treatment system produces 600 kL/day of treated water allowing the mine to produce 4000 tonnes per day of copper, gold, silver, zinc and lead.
Moerk Water are experts in producing sustainable water solutions, regardless of location. Contact Moerk Water today to find out more about bespoke water solutions for your mine site.
