All mines need an effective water management strategy to reduce freshwater consumption and minimise effluents.
The mining sector is Australia’s second largest industry (8.8% GVA), contributing $152 billion to the economy and employing 223,000 people.
Australia’s mines are world-class and owned by some of the largest companies across the globe. They produce raw materials and resources essential to the development of modern society.
Regardless of resource – iron ore, coal, copper, gold, uranium – all mines deal with water; whether it’s from the ground, excess rainfall, or effluents produced from refining.
Over the coming weeks, Westwood Water will investigate important aspects of mine water and effluent treatment in a five-part series:
Part 1 – Sources of Mine Waters and Effluents
Mine waters and effluents arise from many sources depending on the type of mine, local weather patterns, on-site refining processes, and geography.
Wastewater effluent. Source: Wikimedia Commons
Underground mines often penetrate the local water table and require shaft dewatering. Shaft water is constantly pumped to the surface to ensure miners, and expensive mining equipment, are not submerged.
Shaft water from legacy mines is a common source of acid mine drainage (AMD); a corrosive and toxic form of mine water that is is a major global issue.
A local example is the Victorian town of Bendigo, which faces AMD leakage from historical mines which were not correctly rehabilitated upon closure.
The mine shafts in that region are over 100 years old, and the original mining companies are long gone, leaving Bendigo council to deal with the water issue.
Liquid effluents are also generated by mines that have on-site ore processing or refining facilities.
Refining processes use liquid reagents and consume potable (fresh) water, which ultimately adds to the site’s wastewater load.
Some common examples of process effluents are listed below. They are usually heavily contaminated liquids that require significant treatment:
Spent cooling water – used in cooling towers to reduce process temperatures
Quench blowdown – also used to reduce temperature; and to neutralise pH
Used reagents – spent chemical streams from reactors
Rejected brines – highly contaminated liquids often produced by membranes
Yallourn Power Plant Cooling Towers. Source: Wikimedia Commons
A significant amount of mine wastewater is also generated by rainwater, particularly in tropical locations with heavy rainfall.
Contact between rain and mine tailings is another common cause of AMD, with rain leaching (dissolving) metals and sulphates out of the tailings to become acidic.
Mine sites are required to incorporate weather data and rainwater handling procedures while planning their layout and operation strategies.
Although the source of mine waters and effluents can vary, they must be managed correctly and safely; and cannot be discharged without meeting local regulations.
This requires a detailed water management strategy to ensure each site has sufficient water collection, pumping, treatment and storage facilities; and that appropriate discharge licences have been obtained.