Mine water geochemistry and management : two case studies and a new treatment method

[摘要] ENGLISH ABSTRACT:Mine water, that is all forms of water associated with and affected by mining operations is probably thelargest area of concern in the environmental geology of mining.This study looks at the inter-relationship between mine water geochemistry and mine water management.The objectives of this study are:1. To examine major geochemical processes influencing mine water;2. To apply new national water and environmental legislation to the mining industry and discover howmine water management will be regulated;3. To examine the approach of Integrated Catchment Management, and discover how this approach canbe applied to the mining industry;4. To conduct two case studies, where environmental geochemistry, general geochemistry andmultivariate analyses are used as tools to investigate groundwater contamination problems in miningareas, and therefore suggest mine water management interventions; and5. To, considering mine water problems discovered in the case studies, develop a newly-patentedchemical treatment method for possible application in the mining industry.The changing legal framework - principally the implementation of the National Water Act (Act No 36 of1998) and the National Environmental Management Act (Act No 107 of 1998) - is leading to theresponsibilities of a mine becoming substantially clearer, and responsibilities which in the past could havebeen ignored until public outcry will now be difficult to escape.Two case studies are investigated. In both cases, general geochemistry and hydrogeochemistry, coupledwith factor analysis are used to determine the major signatures in groundwater chemistry and the majorsources of contamination. On the basis of this, management interventions are suggested.In the first case study, Sishen Iron Ore Mine of the Northern Cape, three signatures are identified in thegroundwater: a clean dolomitic water signature, and a contamination signature from the mine and onefrom agriculture. The extent of nitrate and diesel contamination is shown to be related to agriculture, theuse of explosives and to mine workshops and depots. Surface water controls may help reduce theseproblems.In the second case study, West Driefontein Gold Mine of the Far West Rand, two signatures are identifiedin the groundwater: a clean dolomitic water signature and a signature relating to contamination from themine. Cluster analysis is used to suggest three groundwater zones, the chemistry of one being fairlyclean dolomitic aquifer, the chemistry of the second affected by the mine and the chemistry of the thirdaffected by granites. Contamination is shown to be related to mining operations, especially the slimes dams, and agriculture. Rehabilitation of dams and dumps, as well as surface water controls may helpreduce these problems.Considering mine water problems discovered in the case studies, a newly-patented chemical treatmentmethod is examined and tested for possible application in the mining industry. It is shown to be extremelyeffective for the removal of calcium from water, but less effective for the removal of iron and manganese.More broadly, this study shows the inter-dependence between mine water geochemistry and mine watermanagement, and the need to be multi-disciplinary in approach.

[发布机构] Stellenbosch University