Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In recent years acid mine drainage (AMD) has become the focus on many mine sites throughout the world. The Witwatersrand gold mines have been the main focus of AMD in South Africa due to their extensive impact on especially groundwater resources. The Witwatersrand Basin is a regional geological feature containing the world-famous auriferous conglomerate horizons. It is divided into sub-basins and the East Rand Basin is one of them. Due to the regional scale of the East Rand Basin AMD issues, a systems approach is required to provide a useful tool to understand the pollution source term and fate and transport dynamics and to aid in environmental decision making and to evaluate the geochemical impact of mitigation measures and evaluate future scenarios. The numeric geochemical models, using a systems perspective, show that the mine waste facilities, specifically the tailings dams are significant contamination point sources in the East Rand Basin, specifically for acidity (low pH), SO4, Fe, Mn, U, Ni, Co, Al and Zn. When the AMD solution enters the soil beneath the tailings, ferrous and SO4 concentrations remain elevated, while Mn, U, Ni and Co and perhaps other metals are adsorbed. After ~50 years the pollution plume starts to break through the base of the soil profile and the concentration of the adsorbed metals increase in the discharging solution as the adsorption capacity of the soil becomes saturated. The pollution pulse then starts to migrate to the shallow groundwater where contamination of this resource occurs. Toe seepage from the tailings either first reacts with carbonate, where acidity is neutralised to a degree and some metals precipitated from solution, where after it reaches the surface water drainage, such as the Blesbokspruit, where it is diluted. Some evaporation can occur, but evaporation only leads to concentration of acidity and dissolved constituents, thereby effectively worsening the AMD solution quality. The mixing models have shown that the dilution factor is sufficient to mitigate much of the AMD, although seasonal variability in precipitation and evapotranspiration is expected to have some influence on the mixing ratio and some variability in the initial solution will also be reflected in variation in surface water quality. From a sustainability perspective, a basic cost benefit analysis shows that the costs for the operating mine and society in general is lower when mitigation measures are employed during operation. For a theoretical mine in the ERB with an operating life of 100 years, the cost of operational mitigation measures is ~R 31 billion. This value is 4% of turnover and 19% of profits over the time period. Post closure remediation costs are ~R 67 billion. This value is 8% of turnover and 41% of profit over the time period. Although the initial capital investment in mitigation measures is substantial, although some measures will be implemented during operation, it is a smaller percentage of profits than eventual post-closure mitigation. / AFRIKAANSE OPSOMMING: In die laaste paar jaar het suur mynwater loging (SML) die fokus geword by baie myn areas regoor die wêreld. Die Witwatersrand goud myne het die hoof fokus van SML in Suid Afrika geword as gevolg van die groot impak wat Witwatersrand SML op veral grondwater bronne het. Die Witwatersrand Kom is ‘n regionale geologiese struktuur wat die wêreld beroemde goud-draende konglomeraat horisonne bevat. Die Witwatersrand Kom word onderverdeel in sub-komme, waarvan die Oos- Rand Kom een is. As gevolg van die regionale skaal van die Oos-Rand Kom SML probleem sal ‘n sistemiese benadering ‘n bruikbare middel wees om besoedelingsbron migrasie en eindpunt dinamika te verstaan asook om omgewingsbesluitneming en die geochemiese impakte en mitigerings metodieke asook toekoms senarios te evalueer. Die numeriese geochemiese modelle, wat vanuit ‘n sitemiese oogpunt beskou is, wys dat die myn afval fasiliteite, veral die slikdamme in die Oos-Rand Kom, beduidende kontaminasie puntbronne is van veral suur inhoud, SO4, Fe, Mn, U, Ni, Co, Al and Zn. Wanneer die SML oplossing die grond onder die slikdamme binnedring, bly Fe2+ en SO4 konsentrasies hoog, terwyl Mn, U, Ni en Co asook ander metale geadsorbeer word. Na ~50 jaar begin die besoedelingsoplossingspluim deur die basis van die grond profile breek. Die konsentrasie van die geadsorbeerde metale neem dan toe in die oplossing wat deur die grondprofiel beweeg het soos wat die adsorpsie kapasiteit van die grond versadig word. Die besoedelingspuls begin dan stadig na die vlak grondwater akwifeer migreer waar dit dan besoedeling van die grondwater versoorsaak. Water wat van die slikdam basis sypel reageer eers met karbonaat, waar suur tot so ‘n mate geneutraliseer word, dat sommige metale uit die oplossing neerslaan, waarna dit die oppervlak water lope, soos die Blesbokspruit, beryk en verdun word. Verdamping van die SML oplossing kan plaasvind, maar verdamping veroorsaak die konsentrasie van suur en opgeloste stowwe, wat die SML probleem dus kan vererger. Meng modelle het gewys dat die verdunning faktor genoegsaam is om baie van die SML te mitigeer, alhoewel seisoenale fluktuasies in reënval en verdampings syfers kan verwag word om ‘n mate van invoed op die meng verhouding tussen die SML oplossing en oppervlak water te hê wat dan in die oppervlak water kwaliteit gereflekteer sal word. Vanuit ‘n volhoubaarheidsperspektief is ‘n basiese koste voordeels analise gedoen. Hierdie analise het gewys dat die koste van ‘n operasionele myn en die samelewening as geheel laer is wanneer mitigasie metodieke tydens operasie toegepas word. Vir ‘n teoretiese myn in die Oos-Rand Kom met ‘n operasionele lewe van 100 jaar, is die operasionele mitigeringsmetodieke koste ~R31 miljard. Hierdie waarde is 4% van die myn omset en 19% van winste oor die tyds periode. Na operasionele remdiasie kostes is ~R67 miljard. Hierdie syfer is 8% van omset en 41% van winste oor die tydperk. Alhoewel die inisiële kapitaal uitleg van mitigasie metodes groot is, alhoewel sekere metodes eers tydens operasie implimenteer sal word, is die uitleg ‘n kleiner persentasie van winste as wanneer remediasie na operasie implimenteer word.

D. Tech. Chemical Engineering / Concerns for the limitations of conventional technology for acid mine water treatment and the potential use of waste water have led to increased interest in membrane technologies. Studying the physical properties of nanofiltration membranes is a very important development in nanofiltration separation process. For optimum separation performance, the nanofiltration membranes have to possess certain physical properties, given the appropriate interactions with solutes in the process stream. This study investigated the performance evaluation of Nano-Pro-3012 and NF90 membranes in the treatment of synthetic wastewater effluents and acid mine water and the influence of membrane characteristics on retention in nanofiltration. The research was aimed to evaluate the performance of a new acid stable nanofiltration material (Nano-Pro-3012) produced by Bio Pure Technology for the removal of heavy metals from shaft 8 at Rand Uranium wastewater treatment plant and compare with a commercially available nanofiltration membrane.

Mine wastewaters generated during active production operations, and decanting streams following mine closure have major environmental impacts, and volumes requiring treatment are expected to increase substantially as the South African mining industry matures. Biological treatment of mine waters has been the subject of increasing interest, where sulphate reducing bacteria are employed for the reduction of sulphate to sulphide, precipitation of metals and the production of alkalinity. However, the sulphide if not removed from the system can be oxidised back to sulphate. As a result there have been limitations especially in the provision of technological options that are sustainable over the long-term, where the total sulphur (in its different forms) can be removed from the system. These, however, are the subject of a number of constraints including, importantly, the process capability to remove reduced sulphur from the treated stream, in one of its oxidation states, and thus linearise the biological sulphur cycle. This remains a major bottleneck in the development of biological wastewater treatment technology. Floating sulphur biofilms are observed as surface layers in numerous aquatic sulphide-rich environments, and it has been suggested that they play a role in the biological cycling of sulphur. The use of sulphur biofilms for the removal of elemental sulphur was identified in this study as a possible means for addressing the technological bottleneck, especially in passive wastewater treatment systems. There is, however, little documented information in the literature on the structure of floating sulphur biofilms, the microbial species responsible for their occurrence or bio-process applications of the system. A linear flow channel reactor was developed to simulate natural conditions and enabled the study of floating sulphur biofilm under controlled laboratory conditions. It was observed that these biofilms developed through three distinct stages termed Thin, Sticky and Brittle films. A microprobe study showed the presence of a steep Redox gradient established across (260 to 380 μm) depth of the floating sulphur biofilm of ~ 0 to -200 mV (top to bottom), which correlated with pH and sulphide gradients across the system. Structural investigations embedded in an exopolymeric matrix containing clearly defined channels and pores. Sulphur crystals were found to develop within the biofilm and above a certain size these disengaged and then settled in the liquid phase below the biofilm. These features, together with the ability of the biofilm to remain suspended at the air/water interface thus provide the surface requirement, and indicate that these structures may be understood as “true” biofilms. In order to study an apparent functional differentiation within the floating sulphur biofilm system, a method was developed to expand its various components over a 13 cm length of agarose tube and across which an oxygen/sulphide gradient was established. This was done by inserting a sulphide plug in the bottom of the tube, overlaying this with the biofilm mixed and suspended in agarose and leaving the tube to open air. After allowing for growth, the different components of the microbial population occurring at various levels across the oxygen/sulphide gradient were sampled. The microbial population was found to resort in distinct functional layers. Aerobes including Acidithiobacillus and Azoarcus, Acidithiobacillus, Thiothrix, Thiovirga and Sulfurimonas were found in the upper oxidised layer. Aerobe and facultative anaerobes such as Chryseobacterium, Bacteroides and Planococcus were found in the middle and heterotrophic anaerobes such as Brevundimonas and uncultured anaerobes were found in the bottom anoxic layer. This enabled the development of a first descriptive structural/functional model accounting for the performance of floating sulphur biofilms. The potential of the floating sulphur biofilm for use as a bioprocess unit operation for sulphide removal in lignocellulose-based low-flow passive systems for acid mine drainage wastewater treatment was investigated. The linear flow channel reactor was scaled up and it was shown that the optimum sulphide removal of 74 % and sulphur recovery of 60 % could be achieved at 20 °C. In a further scale up of the linear channel reactor, the floating sulphur biofilm reactor was developed and operated. Sulphide removal and sulphur recovery of 65 and 56 % respectively was measured in the process. An understanding of the nature and function of floating sulphur biofilms and the further development of their potential application in sulphide removal in aquatic systems may provide a useful contribution to the treatment of acid mine drainage and other sulphidic wastewaters.

M. Tech. Chemical Engineering. / Discusses the HybridICE filter as a new but economical device for separating the ice from the slurry in freeze desalination processes. There is no direct information in the literature on the filter so there is a need to describe the principles behind the operation. There is also a need to investigate the filtering process in order to increase yield and purity of the ice produced. No design method exists for the filter. A design method has to be established so that when the required flow-rate is determined, the dimensions of the filter can be calculated.

D.Phil. (Zoology) / South Africa is a major gold-producing country with the 43 larger mines processing approximately 120 x 106 ton of milled and processed ore and about 30 x I06 ton of mined waste rock. Pollution of both surface and ground water, which can be attributed to the influences of gold-mining, are well known. Acid mine drainage, characterized by a low pH and high concentrations of dissolved metals, and seepage, from active and disused mine-tailings, are two of the main environmental problems associated with gold mining operations in South Africa. A growing concern for the environment and a stricter approach to water pollution by government agencies have made it necessary to investigate the type of effects which the gold mining industry is responsible for, and to develop action to reduce these impacts. The present study focused on procedures to access the effect of gold-mining effluent on the natural surface environment. The study is divided into three separate identities. The mine represented as Ccse study Mine One is considered to be a major contributor of salt loads to the natural stream on the property of the mine. This stream confluences with the Klip River outside the mined area. This mine has only one discharge point of underground mine service water, and is considered to be the main point source of pollution for the mine. As the mine makes use of an open water circuit, the quality and quantity of effluent have a direct effect on the downstream users. It appears that one of the main water quality problems of this open water circuit is the creation of surface water with a very low pH. Part of the problem is the geology of the area which consists of shales, which has a natural low buffering capacity. Because of the low pH the wetlands are not very effective. Metal concentration changes are possibly the direct result of the low pH of the both the water column and sediment. Improving the pH of the surface water can leads to reduced metal concentrations in the water, with possible increased concentrations in the sediment and wetland vegetation. Case Study Mine Two was conducted at a gold mine in the Far West Rand Mine region. The mine can be classified as having a closed water circuit, in that only excess water is discharged. The volume of water discharged is dependent on a number of factors, such as rainfall, wash-down service water and changing demands in sewage treatment systems. The advantage in this type of circuit is that water which has accidentally been spilled can be retained in one of the boundary dams, without the possibility of endangering the downstream users. From the assessment it appears that although the mining activities have influenced the water within the mining area this impact is only confirmed to certain areas. Biotic environmental conditions at certain sites resemble the conditions of the two control sites while other, notably those in contact with processing plants (e.g. metallurgical plant), are far more deteriorated. pH does not seem to be a problem at this specific mine. The main reasons are that the underlying geology of the mine is dolomitic in nature, while the sulphate concentration in the ore appears to be lower than those' found at the Witwatersrand mines. Case study Mine Three is situated in the Klerksdorp gold-mining region. The mine has a complex water circuit as a percentage of the service water is being reused or/and discharged via effluent streams into the Vaal River. Metal concentrations in the sediment core samples indicate a large variability between seasons, sites and depth. Sites in close proximity of slimes dams have high iron and manganese concentrations, whilst those in contact with effluent water from metallurgical plants have relatively high nickel, copper and in concentrations. This can be related to the type of processing material used in the gold-mining process.

M.Tech. (Architectural Technology) / The architectural intervention proposes an urban redevelopment along the mining belt of the city of Johannesburg through the treatment of acid mine drainage. The design research includes a network of selected sites located along the Johannesburgmining belt to address the problem of acid mine drainage,as well as to provide solutions for future urban environments. The main solutions to eradicate the acid mine water problem are infrastructural, which in most cases is associatedwith inhumane environments. A design question addressing the marriage between harsh infrast ructure and humane environments is therefore dealt with ,in an attempt to create a self-sustaining architecture in which infrastructure can have an integrative urban function for the future . The dissertation aims to achive a design intervention that will thread the traces of a mining century into this contemporary African city, through an architecture that will grow into the future of the ever-changing and continuously emergent Johannesburg.

PUMPS mimics natural geothermal vents as a conceptual model designed for the remediation of acid mine water (AMW) in voids of abandoned gold mines of the Witwatersrand Basin in South Africa. In this system, a reaction chamber containing Desulfotomaculum kuznetsovii sulfate reducing bacteria will be set at the bottom of a 3-4 km deep mine that will be flooded. A geothermal system with at least one (1) doublet will be drilled from the bottom of the mine to the depth of 8km, where the temperatures are sufficient for geothermal energy harvesting. AMW, used as a geothermal fluid, will be pumped down the injection well and circulate through hot rock. The hot water is then used to generate electricity and then channelled into the reaction chamber to undergo bio-remediation. Following treatment, the water flows back into the mine voids where it will improve the quality of untreated AMW through dilution. Eventually, the mine will be flooded with clean water that can be stored underground and/or pumped up to surface for social and ecosystem services. Following an introduction and proof of concept for the PUMPS, the research builds further on the technical and economic evaluation of the PUMPS in order to assert its viability and sustainability. The technical viability includes testing the ability for Desulfotomaculum kuznetsovii to survive in high pressure condition; quantifying the amount of energy that can be drawn from the geothermal reservoir; determining the placement and scheme of the geothermal wells; and, finally, developing a robust economic model of the system. Experiments show that Desulfotomaculum Kuznetsovii can tolerate high pressure conditions in of at least 100bar at their ideal sulfate reducing temperature of 63°C. Geochemical modelling shows that AMW can be used effectively as a geothermal fluid for PUMPS. To achieve highest efficiency and minimal fluid loss, the geothermal wells should be placed along the SSE-NNW direction, based on the known stress field across the Witwatersrand Basin. With a flow rate of 30l/s the energy drawn from the geothermal reservoir is sufficient to drive PUMPS and the surplus energy is determined by the volume of AMW treated per day. All results indicate that the PUMPS is technically and economically viable. The economic model shows that the value and viability of the PUMPS is best reflected with a comprehensive inclusion of potential revenue (for example from chemical solution mining of deep seated gold) and financial/environmental incentives.

M.Sc. (Zoology) / Sediment contamination occurs as a result of various anthropogenic activities; mainly through mining-, agricultural- and industrial practices. Many of the contaminants arising from these activities enter the aquatic system and precipitate from the surrounding water, binding to sediment particles. In the sediment compartment, these contaminants reach concentrations much higher than in solution with the overlying water. Even though the quality of the overlying water may prove acceptable in accordance to water quality uidelines, an aquatic system may still be at risk from the contaminated sediment. If the contaminated sediment were to be disturbed through flooding, bioturbation or changes in the water chemistry, these contaminants will desorb into the water column and as a result be detrimental to life forms in contact and dependent on that water source. Monitoring sediment has been a widespread initiative internationally and has led to the development of various sediment toxicity test methods, including different bioassays. This study focused on sediment bioassays such as the Phytotoxkit-F and Ostracodtoxkit-F, and the Diptera bioassay to assess the sediment quality of the Tweelopiespruit-Rietspruit-Bloubankspruit (TRB) river system in Gauteng, South Africa. This river is known to be impacted by acid mine drainage (AMD) since late August 2002. Exposure of the bioassays to river sediment from preselected sampling sites (Site 1, closest to the mine, to Site 6, furthest from the mine, and Site 7, the reference site) provided an eco-toxicological estimation of the acute toxicity emanating from contaminants in the sediment. Physico-chemical analyses revealed high concentrations of metals and other contaminants in the water and sediment. A general linear decrease in contaminant concentrations was observed from Site 1 to Site 6. The results from the bioassays displayed a similar trend, since there were greater sensitivities (mortalities and growth inhibition) to sediments sampled closer to the mine. Due to high levels of contamination in sediments, compared to the overlying water, and the potential impact on aquatic organisms, sediment toxicity monitoring should be a compulsory requirement for environmental studies in South Africa

MENVSC / Department of Ecology and Resource Management / Mine tailings (MT) have been a global problem due to the environmental impacts the waste generates such as air, soil and water pollution. The detrimental impacts include a global problem such as acid mine drainage (AMD) which has been difficult to cleanup. Several studies have been conducted to find alternative measures in reducing or mitigating impacts such as AMD and air pollution. Several studies have revealed how alumino-silicate mineral waste can be used as raw material to produce construction materials. This study aimed at evaluating the potential of synthesizing a geopolymer material from Musina copper mine tailings. Tailings were characterized for their physicochemical and mineralogical compositions using standard laboratory techniques in order to evaluate suitability in geopolymerization. First section of the results presented physicochemical and mineralogical characterization of the Musina copper tailings together with the bioavailability of the chemical species. It was observed that the tailings are mainly composed of SiO2 and Al2O3 as the major oxides indicating that they are aluminosilicate material. Mineralogical analysis revealed dominance of quartz, epidote and chlorite as the major minerals. The bioavailability assessment showed that largely Cu and Ca are bioavailable and highly soluble in an aqueous solution while Al, Mg, Ni, Co, Cr and Fe have a high proportion in non-labile phase. Second section presented the preliminary results wherein the potential application of Musina copper tailings in geopolymerization was evaluated. The results showed that Musina copper tailings can be used to synthesize a geopolymer material. However, it was recommended that several parameters influencing geopolymerization need to be evaluated. The third section presented the evaluation of optimum parameters that influence the geopolymerization process, which include type of alkali activators, alkali activator concentration, curing temperature, liquid-solid (L/S) ratio and curing regime. It was observed that a mixture of NaOH:Na2SiO3.5H20 at a ratio of 70:30 yields a better geopolymer material. The concentration of 10 M NaOH:Na2SiO3.5H20 at a ratio of 70:30 was observed to be the best that yielded the UCS that is acceptable according to SANS1215 standards. When evaluating curing regime, it was found that the material cured using greenhouse has lower UCS as compared to the material cured using oven. The v effect of temperature showed that the UCS decreases with increasing curing temperature. An admixture of river sand and cement was introduced which resulted in a high UCS of 21.16 MPa when using an admixture of cement. The mineralogical composition of the geopolymer bricks showed formation of secondary minerals such as phlogopite, fluorapatite, diopside and actinolite. Batch leaching conducted on the geopolymer bricks detected high leaching of Na from the bricks. Based on the findings of the study of the raw MT potential to produce geopolymer bricks, it was concluded that the material can be used to produce bricks that are within the SANS 1215 requirements. The study further recommended that the study a focus on using cylindrical moulds, other alkali activators and a mechanical mixer. It was also recommended that the greenhouse be restructured to contain heat within the greenhouse during the evening so as to allow constant temperature within / NRF

This study focuses on Acid Mine Drainage (AMD) in the three basins of the Witwatersrand’s goldfields in the Vaal River System in South Africa. AMD has become a highly contested issue. A difference in its definition exists between two groups of role-players identified in the study: government and consultants/activists/NGOs. This study unpacks the differences in the way AMD is defined, the situation of AMD in each of the three basins and the socio-economic implications caused by AMD. A crucial finding was that these definitions determine how the issue is understood and what solutions these role-players propose. The main purpose of the study was to determine whether the South African government’s policy response was appropriate given the socio-economic impacts of AMD and imperatives of sustainable development. This study concluded that, in the policy, there was no clear indication as to what the socio-economic impacts are, and limited attention was therefore given to these impacts. / Development Studies / M.A. (Development Studies)