Studies about the occurrence and behaviour of emerging organic contaminants (EOCs) in African groundwater are limited, while those in mine water are limited worldwide. The current study explores the occurrence and distribution of EOCs and their use as tracers of surface water and groundwater ingress into mine voids at Springs, South Africa. Nine surface water, 16 boreholes, and 6 mine shafts were sampled during the wet and dry seasons for the analyses of pharmaceuticals, pesticides, hormones, industrial and lifestyle compounds. Sulfamethoxazole, carbamazepine, pesticides, caffeine, and bisphenol A were detected in 100

The concomitant generation of concrete fines as a byproduct during aggregate recycling is problematic in entire concrete recycling system. The properties of concrete fines mostly composed of hydrated cement limits the availability in construction use. Effective utilization of concrete fines must be explored to improve the negative environmental impact from the cement and concrete industries. Developing concrete fines as alternative material is one of promising options. This study investigated the potential of concrete fines as novel neutralizer for acid mine drainage (AMD) to explore the effective use of concrete fines. The neutralization performance, including identification of main substance that provide alkalinity, removal mechanism of As, Fe, and comparison with conventional neutralizers were confirmed by discussing the effect of dosage and particle size on AMD neutralization. The sedimentation performance was determined, and the neutralized sludge that was derived from concrete fines showed good settling properties: compactness, and dewatering ability. Moreover, CO2 emissions in AMD neutralization were considered, and CO2 emission reduction by Ca(OH)2 and CaCO 3 substitution by concrete fines was assessed. This first fundamental investigation of concrete fines utilization in AMD treatment determined the potential for neutralization and established the prime consideration of CO2 emissions.

The large number of remote-sensing datasets available necessitates the development of efficient methods when assessing change between such data. A series of techniques, optimizing the analysis of change detection, specifically on large remote-sensing dataset collections, is demonstrated. Iterative (online) statistical measures for mean and standard deviation give the ability to gain a measure of change over potentially hundreds of datasets without excessive computing power being needed. From this, the coefficient of variation can be used to provide further insight. Using such measures, seasonal change can be detected on outcrop (as opposed to vegetation), illustrating that change detection can be used to further extend a spectral signature for rocks. Twelve Sentinel-2 scenes over a 3 year period were used in this study.

Mine-influenced water (MIW), also popularly known as acid mine drainage (AMD), is one of the pressing environmental challenges that the South African government and the mining industry are currently faced with. MIW is typically characterized by low pH, high acidity and sulfate content, and elevated concentrations of various host rock elements, impacting negatively on the environment at local and regional scales. In South Africa, millions of rands are allocated from the government fiscus to address and mitigate the environmental challenges associated with MIW, mainly through the building of active treatment plants, as in the case of the Witwatersrand Gold Basin. However, MIW treatment or remediation also presents economic opportunities through the recovery of valuable minerals and metals, which could offset the treatment costs. Moreover, treated MIW can represent an alternative source of water for various uses such as industrial, agricultural, recreational, or potable, depending on the water quality achieved. In recent years, nanofiltration has emerged as a promising MIW remediation method owing to several factors, including water recovery, low energy consumption, high efficiency, simple operation processes and the fact that no chemical reagents are required. In this review, nanofiltration is discussed in the context of South African MIW remediation, and its benefits and limitations are examined. The technology is still in its infancy, and some perspectives and research directions are considered.

Mining activities within the Witwatersrand Basin, South Africa, have led to many studies, particularly focusing on the generation of acid mine drainage (AMD) in the basin and the associated environmental effects. This study assesses whether gypsum in the Whitehill Formation is connected to acid rock drainage (ARD) resulting from reactions between the pyrite-bearing shale and carbonaceous rocks. To investigate this, the geochemical, geological and palaeoclimatic settings were investigated and a laboratory experiment with Whitehill Formation rock samples was conducted. XRF data of the rocks and modal analysis were used to determine the mineral composition of the Whitehill Formation. In addition, pH-redox equilibrium (Phreeqc) modelling was used for simulations. The results of this study show that metals precipitated from the water–rock solution form various mineral phases like those of the Witwatersrand Basin. Large-scale dolomite dissolution might not be expected.

This study highlights the usage of deep learning artificial neural networks in the assessment of groundwater vulnerability of a coalfield. The network uses the DRIST model with parameters (depth to water level, recharge, impact of the vadose zone, soils and topographic slope) as training inputs and borehole sulphate concentration as training output. This technique was applied to Witbank coalfield, where acid mine drainage emanating from coal mining operations is a huge concern for surrounding environment and groundwater resources. The generated groundwater vulnerability model was validated with another sulphate dataset not used during model training. The deep neural network model with dropout and decaying learning rate regularisers correlated very well with sulphate data from another source as compared to the index and overlay DRIST model. The approach, differentiated areas in terms of vulnerability to acid mine drainage, which can aid policy, and decision makers to make scientifically informed decisions on land use planning. The approach developed in this research can be applied to other coalfields in order to evaluate its robustness to different hydrogeological and geological conditions.

Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Passive treatment technology has been used successfully worldwide for treatment of contaminated mine water, but its applicability in South Africa is limited. To help understand it’s applicability in the South Africa’s context, a pilot plant consisting of integrated anaerobic and aerobic units, was operated in Carolina, Mpumalanga. Th e main objective was to raise pH levels and remove the contaminants. An overall removal rate of at least 90% was achieved for contaminants such as Fe, Al, Zn, Ni. Overall sulphate was removed up to 30%, with no Mn removal. Deterioration of treated water was due to sludge clogging and depletion of treatment materials. Future investigations will focus on characterisation of organic and alkaline substrates.

Wolkersdorfer, Ch.; Sartz, L.; Weber, A.; Burgess, J.; Tremblay, G. (Editors) Abstract Mine drainage a ects waters locally and regionally and can have far reaching environmental and economic impacts. erefore, it is important to be able to quantify the changes in hydrochemistry and to be able to measure the extent of the impacts of mine waters to be able to assess when mitigation steps need to be taken, and to decide on the best methods of mitigation and remediation based on scienti c baseline studies. We present ndings from a study area that extends from the West Rand Gold eld of the Witwatersrand, South Africa, to Hartbeespoort Dam in the North and that encloses protected national spaces, including the internationally recognised UNESCO site known as the Fossil Hominid Site of South Africa (FHSoSA), locally referred to as the Cradle of Humankind World Heritage Site (COH WHS). e research results highlight a need for further investigations to provide realistic solutions that can be implemented to mitigate potential negative outcomes that mine drainage discharges have on the environment and economy, in-line with national and global legislation to preserve and protect world heritage areas. e ndings have implications for mine water legislation and monitoring in areas of active and historic mining, and for water resource management, in particular where UNESCO sites are located.

The research involves formulating a methodology to automatically map surface acid mine drainage pollutant sources using remote sensing in support of environmental and coal discard management in the Witbank, Ermelo and Highveld coalfields. The spectral uniqueness of acid mine drainage-generated secondary iron-bearing minerals is used to build a decision tree for differentiating these from other minerals depicted from Landsat 8 data. Previously known acid mine drainagegenerating coal discard dumps coincide with the remote sensing mapped minerals (jarosite and haematite). The mapped acid mine drainage sources can be used to plan management and mitigation strategies for the protection of water resources.

Over the years, coal mining in the Mpumalanga Province of South Africa has negatively affected the environment by causing pollution of water resources, land subsidence and spontaneous coal combustion. Previous studies show that in-situ treatment of acid mine drainage (AMD) using coal fly ash (CFA) from local power stations was possible and sludge recovered out of such treatment can be used to backfill mines. In this article, the authors have attempted to understand the leaching characteristics of CFA when placed underground as a backfill material using the mine water leaching protocol (MWLP). The results show that the migration of contaminants between the coal fly ash and the AMD in the mine voids depends on the pH and quality of the mine water. While backfilling mine voids with CFA can neutralize and scavenge between 50% and 95% of certain environmentally sensitive elements from AMD such as Fe, Al, Zn, Cu, Ni, Co and Mn. At this moment, it is also important to point out that certain scavenged/removed contaminants from the AMD during initial phases of backfilling can be remobilized by the influx of acidic water into the mine voids. It has therefore been concluded that, while CFA can be used to backfill mine voids, the influx of fresh acidic mine water should be avoided to minimize the remobilization of trapped contaminants such as Fe, Al, Mn and As. However, the pozzolanic material resulting from the CFA-AMD interaction could prevent such influx.

A hydrogeological investigation on coalfield scale was done using available regional data and spatially spaced monitoring boreholes in order to understand the movement of Acid Mine Drainage (AMD) within the soil, vadose zone and aquifers and predict future impacts of surface coal mining activities for planners and regulators. A data-driven GIS artificial neural network was built using hydrogeological and geochemical parameters to produce AMD transport and attenuation factors for the Witbank, Ermelo and Highveld Coalfields. The transport and attenuation factors produced demarcate the coalfields in terms of the expected rates of transport and attenuation of AMD in the subsurface.

In the last 20 years, the popular mineral systems approach has been used successfully for the exploration of various mineral commodities at various scales owing to its scientific soundness, cost effectiveness and simplicity in mapping the critical processes required for the formation of deposits. In the present study this approach was modified for the assessment of groundwater vulnerability. In terms of the modified approach, water drives the pollution migration processes, with various analogies having been derived from the mineral systems approach. The modified approach is illustrated here by the discussion of a case study of acid mine drainage (AMD) pollution in the Witbank, Ermelo and Highveld coalfields of the Mpumalanga and KwaZulu-Natal Provinces in South Africa. Many AMD cases have been reported in these provinces in recent years and are a cause of concern for local municipalities, mining and environmental agencies. In the Witbank, Ermelo and Highveld coalfields, several areas have been mined out while mining has not yet started in others, hence the need to identify groundwater regions prone to AMD pollution in order to avoid further impacts on the groundwater resources. A knowledge-based fuzzy expert system was built using vulnerability factors (energy sources, ligands sources, pollutant sources, transportation pathways and traps) to generate a groundwater vulnerability model of the coalfields. Highly vulnerable areas were identified in Witbank coalfield and the eastern part of the Ermelo coalfield which are characterised by the presence of AMD sources, good subsurface transport coupled with poor AMD pollution trapping properties. The results from the analysis indicate significant correlations between model values and both groundwater sulphate concentrations as well as pH. This shows that the proposed approach can indeed be used as an alternative to traditional methods of groundwater vulnerability assessment. The methodology only considers the AMD pollution attenuation and migration at a regional scale and does not account for local-scale sources of pollution and attenuation. Further research to refine the approach may include the incorporation of groundwater flow direction, rock-pollution reaction time, and temporal datasets for the future prediction of groundwater vulnerability. The approach may be applied to other coalfields to assess its robustness to changing hydrogeological conditions. (C) 2017 Elsevier Ltd. All rights reserved.

Surface water and groundwater quality in areas of South Africa continues to be degraded by acid mine drainage (AMD), a legacy of coal mining. The majority of abandoned coal mines consist of complex multiple level workings connected to a drainage tunnel discharging AMD, in lower lying regions. This decanting mine water poses severe problems to the receiving environment. Thus, there is a need, to define hydrologic connectivity between surface water, groundwater and mine workings to understand the source of both water and contaminants at the decanting points. South Africa has limited studies into the feasibility of using tracer techniques, especially in mine water studies to understand underground water dynamics. Locally, there are no regulations and/or standard procedures for such activities. Wolkersdorfer (2008), states that in some countries such as Germany, there are regulations that govern the use of tracers. In a case study that is currently in progress as part of the use of tracers in mine water, water samples were collected from different discharge points in and around a flooded and abandoned coal mine, within the Witbank coal fields of the Permian Karoo Supergroup. This was done to classify the different water types as a pre-assessment for using tracer techniques. Our preliminary results demonstrated that the water samples collected have high concentrations of major elements such as SO4, Cl, Na, Mg, Al, K, and Ca.

Acid mine drainage from abandoned mines is primarily responsible for degradation of scarce water resources in South Africa. Owing to the nature of previous legislations, the South African government has inherited environmental liabilities of most of the abandoned mine sites, and hence there is a need to develop long-term sustainable remediation solutions. To contribute towards development of sustainable mine water management solutions in South Africa, a pilot passive treatment plant consisting of integrated anaerobic and aerobic units has been constructed to treat 1440 liters of acid mine drainage per day from an abandoned underground coal mine. During the first six months of operation, the pilot plant has successfully neutralized the water and substantially removed contaminants, such as Fe, Al, Co, Zn, Ni, As, Pb, V, but with limited SO4 reduction (only 30% removal rate was achieved). Thereafter, there has been a decrease in treated water quality with time, and this was largely due to clogging and/ or depletion in the treatment materials. The study demonstrated that passive treatment can be used as a long-term remediation of polluted mine water from abandoned mine sites in South Africa. The results of this pilot-scale test will be used to design an optimised full-scale plant, and also assist in an optimized design of additional pilot plants in other abandoned mining areas.

Following the cessation of underground mining in the three original mining complexes in South Africa's Witwatersrand Gold Field, mines started to flood with no control measures in place. In 2002, acidic water began to discharge from the West Rand Gold Field's underground workings, negatively impacting on the downstream environment, with impacts identified in both surface and underground water. In the years following this, underground operations ceased in the Central Rand and East Rand Gold Fields and the underground workings were allowed to flood. Three approaches have been identified for the management of the flooded underground workings:. Flooding and management of the discharge at surface. Maintaining the water level at a pre-determined safe level, locally referred to as an "environmental critical level" by pumping. Controlling the water level in the underground workings by means of a discharge tunnel. Currently, pump and treat programmes are at various stages of development and implementation in the three original gold fields. Planning for these has been severely hampered by a lack of reliable historical data on volumes pumped. The absence of supporting data also led to the selection of conservative environmental critical levels, which will be extremely costly to maintain. Adjustment of the environmental critical levels in the Witwatersrand Mines would require a good understanding of both the hydrodynamics of the relevant underground mine workings and the local hydrology and hydrogeology in the areas likely to be impacted, but would reduce pumping costs and could allow the implementation of gravity-driven drainage in some areas. It may also have a positive impact on the rate of flow into the underground workings and on the water quality in the longer-term.

In South Africa’s Witwatersrand mining area, the issue of acid mine drainage has risen to great public prominence, with community-based activists playing an important role in raising awareness. Conventional water quality monitoring is costly and often requires complex procedures. However, simple water quality tests exist for a number of parameters which can be used to identify potential contamination related to mining. These have been applied as part of a high school science project, looking at the environmental impact of gold and uranium mining in the upper Wonderfonteinspruit. The results allow identification and characterisation of water pollution. This demonstrates the ability of volunteer monitoring programmes using simple technologies to complement the work done by regulators, operators and researchers in mining environments.