ACID MINE DRAINAGE AND THE IMPACT ON GROUNDWATER

Several industrial – and mining activities has caused serious environmental impacts and environmental degradation. One typical impact on the direct environment and water quality caused by mining operations, includes Acid Mine Drainage. This has become arguably, one of the most serious environmental concerns especially in South Africa. Acid Mine Drainage occur when different chemical reactions such as ion exchanges, mobilization and precipitation of ions and / or groups of ions takes place. With the focus on Sulphate (SO4) related chemical reactions (not limited to), Sulphates are one of the most important reactions in this regard and is a fair representation of pollution at various mine types. Sulphate related reactions take place when it enters the groundwater system through oxidation of pyrite through chemical weathering, mining, washing or percolation through stockpiles of the host material, especially coal dumps or other tailings facilities. An example of such a reaction is: 2FeS2 + 7O2 = 2FeSO4 + 2H2SO4. Pyrite + Oxygen = iron sulphate + sulphuric acid Iron sulphate forms, as well as sulphuric acid (H2SO4), causing decreases in the groundwater pH and mobilisation of metal ions (that are usually more soluble at a low pH). The acidic pH has significant consequences with contaminated soil, vegetation, and water as the result.

Additional problems associated with Acid Mine Drainages include:

  • Contaminated drinking water;
  • Disrupted growth and re-production of aquatic plants and animals; and
  • Eroding effects of acid on parts of infrastructures such as bridges.
The problem normally occurs during mining closure phases, or at abandoned, derelict and defunct mines, and is a continuing by-product of current mining activities.

Mitigation and management are crucial to minimize the overall impact the mining environment is to have on our resources. To decrease penetration of air and water through waste piles by covering (through wet or dry soils) over the exposed material, can be an effective remediate response.

Environmental Assurance specializes in assisting our clients for optimum mitigation measurements and actions. For resource-specific programme design, implementation and monitoring services, please do not hesitate to contact our highly qualified specialists for a proposal on 012 460 9768 or info@envass.co.za

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