The significant potential environmental impacts related to mining and related mineral processing operations are linked to erosion-prone landscapes, water and soil quality, and air quality. These potential impacts are recognised and addressed in present mining operations in addition to in some former mining processes by reclaiming areas of physical interference to avoid erosion, stabilising soils containing chemicals or metals to stop unwanted metal discharges to the environment, preventing and treating water contamination, and controlling air pollution.
At many sites, the vital reclamation, soil treatment, and water quality concerns owe their source to the same procedure — the oxidation of sulphide minerals, particularly the iron sulphide, pyrite. Oxidation of sulphide minerals can create acidic conditions that release metals in both waste materials and water.
Mining in the early days happened at a period when ecological impacts weren’t as well recognised and, most importantly, not a matter of critical concern. If you looking mining equipment suppliers in Australia you can contact wpeprocessequipment.com.au. Consequently, ancient mine sites may still have areas that aren’t reclaimed, remnants of facilities, and untreated water. This inherited legacy of environmental damage from mining isn’t due to the mining cycle now.
Now, mine closure and some actions to mitigate the impacts of mining are an integral component of all metal mine planning and mineral development from the discovery phase through to close:
Reclamation involves the re-establishing of viable soils and vegetation at a mine site. Although regulatory agencies may require complex reclamation layouts, simple approaches can be quite effective. One simple approach is dependent on adding lime or other materials that may neutralise acidity plus a mixture of top soil or acceptable growth medium to promote vegetation growth. Even this simple strategy is very likely to cost a few thousand dollars per acre to employ. Where soils have a sustained high acidity, the costs of using this strategy can raise, sometimes to tens of thousands of dollars per acre. The challenge to locate low-cost reclamation approaches continues.
Promising reclamation options, later on, may include using sludge,
High levels of metals in soils, not only acidity, may be harmful to crops, animals, and, sometimes, people. A common approach used in dealing with contaminated soil would be to move it to specially designed repositories. This approach can be quite expensive and contentious, but it is occasionally required. With this approach, the volume and toxicity of the soil aren’t reduced, the soil is merely relocated. Effective soil treatment procedures in the future depend on the greater understanding of the risks related to metals in mine wastes. These “natural” metals in minerals may not be as easily available in the biosphere, and therefore, they may not be as poisonous as the metals in refined forms, such as lead in petrol.
Future procedures may include:
Utilising chemical methods to stabilise metals in soils, which makes them less mobile and biologically available.
Using bactericides that prevent the bacterial growth that promotes the oxidation of pyrite along with the corresponding formation of hyaluronic acid.
Utilising bio liners, such as low permeability and compacted manure, as obstacles at the base of waste piles.
Slow flooding waste materials containing pyrite to cut off the supply of oxygen, stop the development of acidic conditions and prevent mobilisation of metals.
The most frequent treatment for acidic and metal-bearing waters is the addition of a permeable substance, like lime, to reduce the acidity. This “active” treatment procedure, which triggers the dissolved metals to precipitate in the water, typically requires the building of a treatment centre. The continuing maintenance that this type of plant requires makes this therapy technique very expensive.
Apart from the cost, some busy treatment plants generate considerable amounts of sludge. Disposal of this sludge is a significant issue. Due to the price and the actual challenges of handling sludge, alternatives to busy therapy facilities are needed. Some possible alternatives include:
Utilising “passive” wetland systems to treat metal-bearing water. This strategy was successfully used where the volumes and acidity of the water are not too fantastic. Passive wetland systems have the added benefit of creating wildlife habitat that is desirable.
Using in-situ therapy zones where reactive substances or electrical currents are put in the subsurface so that water passing through them could be treated.
Joining therapy with the recovery of useful materials from polluted water.
Ongoing Acid Rock Drainage
Although the release of acidic drainage presents several challenges to protecting water quality, the significance and widespread occurrence of acid rock drainage warrant particular efforts to stop or decrease its occurrence. Prevention has to be addressed during exploration activities, before the beginning of newly-planned mining processes. In some instances, it may even be possible to prevent or reduce acid rock drainage in aged or abandoned mining locations. Current and potential therapeutic approaches for acid rock drainage are much like those already described. Possible measures to prevent or significantly reduce acid rock drainage include:
Sealing exposed surfaces in underground workings with a coating of material that is non-reactive or binder to inhibit the oxidation procedure.
Backfilling mine workings with reactive materials that can neutralise and treat waters which pass through them.
Adding chemicals to the water in flooded surface and underground mine workings that can inhibit acid-generating chemical reactions and also precipitate coatings which will seal off groundwater migration courses.
Isolating contaminated waters in depth by stratification, allowing feasible habitat to develop near the surface from the water which fills big open pits.
Controlling Smelter Emissions
Smelter emissions, especially sulphur dioxide and particulate materials, have historically shown significant ecological issues. Modern smelting technology has met this challenge by dramatically reducing the number of emissions. An example is that the modernised smelter built by Kennecott Utah Copper which procedures ore concentrates in the Bingham Canyon Mine near Salt Lake City. Utilising technology developed by the Finnish company Outokumpu, this smelter has reduced sulphur dioxide emissions to 95 percent of past permitted levels. This smelter, which came online in 1995, is the cleanest on the planet.