The effects of chrome mining activities on the water quality of the Hex River in the Rustenburg area: case study on Kroondal chrome mine

[摘要] This study assesses the water quality status of the Hex River downstream of Kroondal Mine(KMS15, sampling point located downstream of Kroondal Mine) and the effects of miningactivities (Kroondal Chrome Mine) on the water quality of the Hex River in Rustenburg,which is in the North West Province of South Africa. Potential pollutants were identified,quantified and their distribution was determined over seven years (2007 to 2013) alongdifferent sampling points upstream and downstream to the mine. Water quality-monitoringdata was obtained from the mine. The surface and underground water was sampled on amonthly basis and analysed by Aquatico, (a water quality service provider of KroondalChrome Mine) at SANAS Accredited Testing Laboratory (No T0374).Data was collected for the Hex River and its tributary; the nearby discharge from CrocodileFarm and Farm Dam; as well as mine containment dams, slimes dams, run-off from theprocessing plant and water dams within the mine. Descriptive statistics (mean/average,minimum and Maximum) and box plots are used to explain the water quality at all samplingpoints. Water quality from sampling location points was compared against the Total WaterQuality Guideline Range (TWQGR) for irrigation, livestock watering, ideal domestic use,aquatic ecosystem limits and the exemption permit issued to the Kroondal Chrome Mine bythe Department of Water Affairs and Forestry (DWAF) in 2007, now Department of Waterand Sanitation (DWS).The water quality of the Hex River, downstream of Kroondal, was described as neutral,alkaline, saline and very hard with a high pH, and a high concentration of Electricconductivity (EC), Total Dissolve Solids (TDS), Chlorine (Cl), Sulphate (SO4), Nitrate (NO3),Ammonium (NH3), Hardness (CaCO3) and Orthophosphate (PO4). Pollution sources andpathways were identified using the study area layout and by conducting an impact pathwayanalysis using annual descriptive statistical (annual mean or average values) of water qualitytables generated by SAS enterprise 6.1 (a software used to analysed descriptive statistics ofthe mine water quality data) for a period 2007 until 2013, and box pots graphs showingmonthly water-quality data for pH, EC, TDS, Cl, SO4, NO3, NH3, CaCO3 and PO4 at 15monitoring localities between Kroondal Chrome Mine, the Hex River and its tributaries(Kroondal tributary and Sandspruit) over seven years. It was concluded that thesurface/groundwater of the Kroondal Chrome Mine process – such as seepage from slimesdams, plant run-off and the vent shaft underground water dam – had an influence on thewater quality of Hex River with regard to the discharge of pH modifying pollutants, EC, TDS,Cl, SO4, NO3, NH3, CaCO3 and PO4. Other pollution sources were discharge from CrocodileFarm and Hex River, as well as the Sandspruit upstream sources such as mining (platinumand chrome), industries’ municipal sewage treatment works, agricultural activities andinformal settlements activities.Mine pollutants or constituents were identified as a unique example of the compound impactof weathering, hydrologic and anthropogenic processes such as the increased use ofexplosives containing NO3 and NH3 underground. The chemical compositions of surfacewater in the mine sampling location were strongly influenced by rock water in tractions,dissolution and dilution, as well as anthropogenic inputs. Key insights drawn from the studyis that, cumulative impacts in the Hex River catchment present different issues, roles andresponsibilities for industries, government/ regulators and community stakeholders. Practicaland cooperative management of cumulative impacts by catchment stakeholders can benefitregional environments and communities of Rustenburg and the North West Province atlarge. This study demonstrates the usefulness of descriptive statistical techniques foranalysis and interpretation of complex data sets, water quality status of the Hex Rivercatchment, influence of the Kroondal Chrome Mine (KCM) waste water to the Hex Rivercatchment, pollution sources and pathways from different activities around Hex Rivercatchment. Best practice water management was recommended to form part of the KroondalChrome Mine environmental objects, target and management plan as well as the mine riskprofile. Cumulative management dimensions, approaches and/or methods wererecommended for all Hex River catchment stakeholders including Department of Water andSanitation (DWS), mines, farmers, industries and disadvantage communities along thecatchment.

[发布机构] University of the Witwatersrand