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Thesis (MPhil)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Ecosystems, and the very services and resources that they provide, are fundamental to our existence. Regardless, mankind shows scant regard for the biotic and abiotic components of the environment that serve as both sources and sinks for anthropocentric demands, practices and behaviours. Of these vital resources, perhaps the one that is most under threat is water which while crucial for growth and development around the globe, is rapidly becoming a scarce commodity. In South Africa - already a water-scarce country - this situation is further compounded by mining practices that are not only unsustainable, but also largely unregulated from an environmental perspective. Mining activities have resulted in the mass exposure of iron pyrite and heavy metals, both underground and on the surface. Upon exposure to weathering, the iron pyrite gives rise to sulphuric acid, which, in turn results in the mobilisation and concentration of toxic metals. Although this is a geological phenomenon, the increasing concentrations of toxic metals as a result of mining have exposed the Gauteng province to enormous environmental, social and economic risks. Concerning the risks, the research highlighted the following: - Although comprehensive research has been found relating to the physical attributes of acid mine drainage (AMD), very little is known of the health aspects associated with AMD. Of immediate concern is, the subsequent environmental and health implications stemming from the association between living organisms and heavy metals. - In the absence of such information, the credibility of current solutions is thus questionable. Of the solutions that have been proposed, most have been reductionist in approach and have only focused on dealing with the surface decant of contaminated water from predominately non-functioning mines. The health risks associated with radioactive and highly toxic waste have been down played or simply ignored (Albrecht, 2011). - The absence of a comprehensive solution also raises questions as to the assessment and decision-making process utilised to date by the Department of Water Affairs (DWA). - Both government and the private sector have allowed the AMD threat to amplify over the years. Their inaction has been facilitated by the poor enforcement of legislation and, clever manoeuvring by mining companies, in what can only be described as a mutually beneficial relationship between government and the mining industry. In stark contrast to the inaction of government and the private sector, environmental activists have been very vocal in calling for a solution to a number of the risks associated with AMD. This, together with the recent decant of AMD in the Western Basin, has culminated in a public outcry and prompted calls for a solution to the AMD threat. Government's response to this was a narrow and incomprehensive solution, which only served to further frustrate the different stakeholder groups. Where stakeholders have different themes as to the implications and thus solutions to the AMD threat on the Witwatersrand (as driven by the profiles of the different stakeholder groups), an appropriate solution will only be realised by adopting the following recommendations: - Government must show the necessary political will, to fully engage the threat of AMD and address their poor track record as regulator - their credibility has been skewed through their vested interests in the mining industry. - Having taken ownership of the AMD threat on the Witwatersrand, government must move to avert any immediate risks to human well-being. - Under governments' leadership, the capacity of all stakeholders must be addressed to facilitate a participatory trans-disciplinary review of the assessment mechanisms and facts, in order to reach a mutually acceptable solution(s) to the social and environmental impacts associated with mining activities - a solution that will ensure future environmental integrity, social development and economic growth. / AFRIKAANSE OPSOMMING: Ekosisteme, en die dienste en hulpbronne wat dit voorsien, is grondliggend aan die mensdom se bestaan. Tog toon die mensdom weinig respek vir die biotiese en abiotiese komponente van die omgewing, hoewel ons met ons behoeftes, praktyke en gedrag daarop staatmaak én daaraan afbreuk doen. Van hierdie lewensnoodsaaklike hulpbronne is die mees bedreigde waarskynlik water, wat – hoewel dit vir groei en ontwikkeling wêreldwyd van deurslaggewende belang is – spoedig besig is om ʼn skaars kommoditeit te word. In Suid-Afrika, wat in elk geval ʼn waterarm land is, word hierdie toedrag van sake vererger deur mynboupraktyke wat nie net onvolhoubaar is nie maar ook ongereguleerd. Mynboubedrywighede het gelei tot die massablootstelling van ysterpiriet en swaarmetale, sowel ondergronds as op die oppervlak. Wanneer ysterpiriet chemies verweer, vorm dit swawelsuurwater, wat op sy beurt toksiese metale mobiliseer en konsentreer. Hoewel dít ʼn geologiese verskynsel is, het hierdie verhoogde konsentrasies as gevolg van mynbou die Gautengprovinsie aan enorme omgewings-, maatskaplike en ekonomiese risiko’s blootgestel. Wat die risiko’s betref, beklemtoon hierdie studie die volgende: - Hoewel omvattende navorsing oor die fisiese kenmerke van suur mynwater (“acid mine drainage” – AMD) onderneem is, is weinig bekend oor die gesondheidsaspekte wat daarmee gepaardgaan. Wat tot dusver van onmiddelliker belang was, was die omgewings- en gesondheidsimplikasies wat daaruit voortvloei wanneer lewende organismes aan swaarmetale blootgestel word. - In die afwesigheid van sodanige inligting is die geloofwaardigheid van huidige oplossings dus twyfelagtig. Die meeste van die oplossings wat voorgestel is, is reduksionisties van aard en beklemtoon slegs die hantering van besoedelde water wat op die oppervlak uit hoofsaaklik onaktiewe myne sypel. Die gesondheidsgevare wat met radio-aktiewe en hoogs toksiese afval gepaardgaan, word geheel en al onderspeel of bloot misgekyk (Albrecht, 2011). - Die gebrek aan ʼn omvattende oplossing laat ontstaan ook vrae oor die beoordelings- en besluitnemingsprosesse wat die Departement van Waterwese oor die jare sowel as meer onlangs gevolg het. - Sowel die regering as die privaat sektor het toegekyk hoe die bedreiging deur suur mynwater oor die jare vererger. Dié gebrek aan optrede is aangehelp deur swak wetstoepassing sowel as slimmer bewimpeling deur mynboumaatskappye in wat eenvoudig as ʼn wedersyds voordelige verhouding tussen die regering en die mynboubedryf beskryf kan word. In skrille kontras met die regering en privaat sektor se traagheid het omgewingsaktiviste nog nooit geskroom om hul stem te verhef en op oplossings vir baie van hierdie risiko’s aan te dring nie. Dít, tesame met die onlangse uitvloei van suur mynwater in die Westelike Kom, het op openbare protes uitgeloop en aanleiding gegee tot oproepe om ʼn oplossing vir die bedreiging van suur mynwater. Die regering se antwoord hierop was ʼn eng, beperkte oplossing wat die verskillende belangegroepe slegs verder frustreer het. Aangesien belangegroepe (in ooreenstemming met hul uiteenlopende profiele) verskillende aspekte van die implikasies van – en dus ook die oplossings vir – die bedreiging van suur mynwater aan die Witwatersrand beklemtoon, sal ʼn toepaslike oplossing gevind word slegs deur die volgende aanbevelings te aanvaar: - Die regering moet die nodige politieke wil toon om die bedreiging van suur mynwater ten volle die hoof te bied, en moet daadwerklik verbeter op sy swak prestasiegeskiedenis as reguleerder, waarin hy heelwat geloofwaardigheid ingeboet het vanweë regeringsbelang by die mynboubedryf. - Nadat die regering sy verantwoordelikheid rakende die bedreiging van suur mynwater aan die Witwatersrand aanvaar het, moet hy dringend optree om enige onmiddellike gevare vir menslike welstand te voorkom. - Onder leiding van die regering moet die vermoëns van alle belanghebbendes betrek word ten einde ʼn deelnemende, kruisdissiplinêre beoordeling van die meganismes en feite te onderneem, om sodoende (ʼn) wedersyds aanvaarbare oplossing(s) vir die maatskaplike en omgewingsimpak van mynboubedrywighede te bedink – ʼn oplossing wat die integriteit van die omgewing, maatskaplike ontwikkeling en ekonomiese groei sal verseker.

A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Environmental Science Johannesburg, November 2012. / Acid rock drainage (ARD) and dust are potential consequences of gold and uranium mine residue deposits (MRDs) on the Witwatersrand basin. Urbanisation has taken place around mines and, with the curtailing of mining activities and clearing of land previously covered by MRDs, there is pressure to use this land for residential, industrial and agricultural purposes. However, mining companies historically were not required to provide pollution control measures and there is evidence for contamination of land and water. Thus, there is a need to prioritise contamination sources for mitigation and to understand the extent of contamination and potential risks associated with different categories of land-use on mining land. The aim of my study was to conduct a first-order risk assessment to aid in identifying vulnerable land use in the vicinity of gold and uranium mining, and prioritising MRDs, including footprints, for mitigation. To achieve this I constructed a Geographical Information System (GIS) using publicly available spatial data, and then tested the usefulness of historical aerial photographs and remote sensing imagery for mapping MRDs and impacts of MRD origin under Highveld conditions (i.e. a seasonal climate with summer rainfall and annual evapotranspiration of >2.5 times mean annual precipitation). The Ekurhuleni Metropolitan Municipality (EMM; 1923 km2) is an area of extensive historical mining with major urbanisation, while retaining areas for agricultural land use; thus it was selected as a representative study site. I used a numerical rating scheme, which combined a number of parameters in two separate stages to calculate a risk index. The first stage involved the classification of hazards associated with MRDs while the second involved an assessment of land use vulnerability based on exposure pathways and proximity. Historical aerial photographs (1938, 1964 and 2003) and the Chamber of Mines (CoM) Dump Indexes were used to identify and classify MRDs in terms of basic geotechnical properties, current status and historical failure. Multi-spectral data, acquired over two years (2002 and 2003) in two seasons (spring and summer) by the TERRA satellite’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor, were used to compile thematic images, indicating potential contamination of surrounding land. It was intended that a zone of influence could be distinguished for each MRD enabling me to rate the hazard severity. The thematic images I selected included primary minerals (pyrophyllite and chlorite), secondary minerals (copiapite and jarosite), an indicator of uranium-bearing ore (referred to as mincrust) and the normalised difference vegetation index (NDVI). These minerals were chosen as potential indicators of different transport routes of contaminants and I tested their associations with different features and land use. I also tested for seasonal differences in the detection of these minerals, and used NDVI to examine the masking effect of active vegetation. I found GIS to be well suited for combining the various forms of spatial data and providing information about MRDs, aqueous pathways, proximity to vulnerable land uses and impacted areas. However, I found that the potential severity of the hazards posed by each MRD, as indicated by a zone of influence, could not be determined from aerial photographs and ASTER alone. I therefore utilised the findings expressed in the literature survey to assign ratings for the different classes of MRDs. The vulnerability assessment was also supplemented by literature review to rate land uses based on human exposure pathways. I determined that MRDs (including footprints) cover 4.1% of EMM, with slimes dams, totalling 3.5%, occupying the majority of this area. I found that 64% of slimes dams had failed prior to 2003 and I plotted a further 0.6% of EMM covered by visible mine residue spillage. Fifty three percent of MRDs were situated within 100 m of drainage lines or old wetlands, while 52% of these (i.e. 27% of the total) had been constructed in the watercourse. I also found that 15% were constructed on dolomites. Informal settlements were located on or bordering 6% of MRDs, with 41% of MRDs within 1 000 m. Eighty eight percent of MRDs were found within 1 000 m of formal residential areas, 71% within 500 m, and formal settlements were located on or bordering 5% of MRDs. Twenty three percent of MRDs were located within 500 m of agricultural land, while 35% were within 1 000 m; and industrial land use was on 9% of MRDs (footprints), with 40% of MRDs being within 500 m of industrial areas and 61% within 1 000 m I found that chlorite did not provide a ‘signature’ of gold and uranium mine residue, whereas the other four minerals did. I also found that, of the two seasons examined (spring and summer), the best time to take an ASTER image to detect mineral signatures of gold and uranium mine contamination is after a few dry days following the first spring rains. For this reason, I used the ASTER taken in late October (spring) 2003 to examine associations with pathways and land use. I found more pyrophyllite and copiapite on industrial and business land use than background, which I suggest is associated with the settling of windborne dust on large and flat roofs; although, in the case of copiapite this could be related to the oxidation of settled wind blown pyrite material. I found jarosite to be a reliable indicator of mine residue, which, together with mincrust, helped me identify contamination in former agricultural holdings, which are now a township. Although, chemically undefined, mincrust was a useful indicator of contamination, as I found it to be reliably detected on MRDs (including footprints), mine residue spillage, wetlands and other contaminated sites, and absent from known uncontaminated sites. Furthermore, it was not necessarily masked by active vegetation, whereas copiapite, jarosite and pyrophyllite were. Mincrust was also detected on irrigated agricultural land with an odds ratio of between 10 to 36 times greater than for rain-fed. Consequently, the most likely pathway for mincrust is the aqueous. The mincrust signature, together with historical aerial photographs, also assisted me to identify historical mining along Black Reef outcrops, through detection in a wetland upstream of known mining activities. The culmination of my study was a risk class and index for MRDs from which ‘risk maps’ were produced. These maps provide a guide to the level of risk posed by each MRD to the surrounding land use. Of the total 287 MRDs (including footprints) identified in the EMM, 50% were classified lower-risk; 40% medium-risk; 10% higher-risk and 0% as much higher risk. The lower-risk MRDs were predominantly rock dumps, whereas the higher-risk MRDs were slimes dams. The findings from my study will contribute to meaningful recommendations for future land use and enable mining companies, landowners, developers and government to allocate their resources judiciously (i.e. appropriate to the level of risk). The results of this study have been published as: Sutton, M.W., Weiersbye, I.M., Galpin, J.S and Heller, D., 2006. A GIS-based history of gold mine residue deposits and risk assessment of post-mining land uses on the Witwatersrand Basin, South Africa. In: A. B. Fourie and M. Tibbett (eds.), Mine Closure 2006: Proceedings of the 1st International Seminar on Mine Closure, Perth, ISBN: 0-9756756-6-4, pp. 667–678 (Appendix I). Sutton, M.W. and Weiersbye, I.M., 2007. South African legislation pertinent to gold mine closure and residual risk. In: A.B. Fourie, M. Tibbett and J. Wiertz (eds.), Mine Closure 2007: Proceedings of the 2nd International Seminar on Mine Closure, Santiago, ISBN: 978-0-9804185-0-7, pp. 89–102 (Appendix II). Sutton, M.W. and Weiersbye, I.M., 2008. Land use after mine closure – Risk assessment of gold and uranium mine residue deposits on the eastern Witwatersrand, South Africa. In: A.B. Fourie, M. Tibbett, I.M. Weiersbye and P.J. Dye (eds.), Mine Closure 2008: Proceedings of the 3rd International Seminar on Mine Closure, Johannesburg, ISBN: 978-0-9804185-6-9, pp. 363–374 (Appendix III).

[pt] A drenagem ácida de minas (DAM) é um problema ambiental capaz de comprometer a qualidade dos recursos hídricos, que decorre da oxidação de sulfetos. A adoção de medidas corretivas e/ou preventivas dependerá do programa de predição escolhido, este geralmente inclui testes do potencial de geração de acidez (método estático), e da velocidade com que ocorre o processo (método cinético). No presente trabalho avaliou-se o potencial de geração de DAM usando o teste de Balanço Ácido Base Modificada (BABM), e monitorou-se a qualidade da água da drenagem dos rejeitos, durante 23 semanas, usando o método das colunas de lixiviação segundo a Acid Drainage Technology Initiative, para amostras de rejeitos provenientes da Carbonífera Criciúma e da Carbonífera Metropolitana. As duas amostras da Carbonífera Criciúma (SRA e SRB) apresentaram potencial de geração de acidez e as amostras da Metropolitana apresentam um pequeno risco de gerar acidez, segundo os resultados do BABM. Porém os resultados do método cinético, para todos os casos, mostram valores de pH menores que 4 e valores crescentes para a concentração do SO4 -2, acidez e o Eh, que mostra que são geradoras de DAM. Deve se ter em conta que o teste de BABM não leva em consideração a cinética das reações para a produção de acidez e sua neutralização. Os valores de concentração para o Zn, Mn e Al excedem os padrões de qualidade de água (segundo a Resolução No 357, CONAMA). No caso do Pb, os resultados não foram conclusivos devido ao alto limite de detecção do equipamento. Utilizando o modelo do núcleo não reagido, a etapa controladora da taxa de oxidação para a pirita (de FeS2 a SO4 -2) para as amostras SRA e SRB foi transferência de massa através da camada limite, com tempos teóricos para conversão completa (t) de 2,7 e 1,6 anos respectivamente, para as condições ensaiadas. A outra amostra da Carbonífera Criciúma (VR) apresentou como etapa controladora nas semanas iniciais a transferência de massa através da camada cinza e nas semanas finais a reação química propriamente dita, sendo t estimado em 3,4 anos para as condições ensaiadas. / [en] The acid rock mine drainage (ARD) arising from sulfides oxidation in mining areas is a serious environmental problem that markedly affects the quality of the surrounding water. Choosing the measure for remediation and/or preventing pollution effect depends on a suitable evaluation through a prediction program, it has principally tests of the acid generation potential (static method), and rate of the corresponding chemical reactions (kinetic methods). The present study aimed to evaluate the potential of ARD of wastes from two coal mines Criciúma and Metropolitana, using a Modified Acid Base Accounting (MABA) and evaluated the drainage water quality during 23 weeks using leaching columns test according Acid Drainage Technology Initiative protocol. According MABA results two coal mine Criciúma Samples (SRA e SRB) indicated an acid generation potential, and Metropolitana samples present a small risk to generate acidity. However the kinetic method results, for all the samples present pH < 4 and increasing concentrations values for SO4 -2, acidity and Eh that indicate acid generation potential. The MABA test does not consider the reaction rate of acid production and its neutralizations reactions. The concentrations values of Zn, Mn and Al exceeds water quality standard (Resolução No 357, CONAMA). In the case of Pb the results were inconclusives due to the equipment high detection limit for this element. Shrinking Core Model was used to determinate rate control to pyrite oxidation kinetic (de FeS2 a SO4 -2). SRA and SRB samples the layer diffusion control was the control rate, with complete conversion theoretical time (t) of 2.7 and 1.6 years, respectively, for the test conditions. The Criciúma Coal Mine sample (VR) presents product layer diffusion as control rate at the beginning weeks and then the chemical reaction was the control rate at the final weeks of the test and for this control the calculated t was 3.4 years for the test conditions.

O presente trabalho teve, por objetivo principal, analisar a remoção de sulfato em águas de drenagem ácida de minas em dois tipos de reatores anaeróbios, um com crescimento granular (UASB) e outro com biomassa aderida (RAHLF). Estudos anteriores publicados na literatura apresentam resultados positivos quanto ao tratamento anaeróbio de drenagem ácida de minas, entretanto, na maioria deles, é aplicado um tratamento preliminar à água residuária antes do tratamento principal. Esse trabalho avaliou a operação de reatores anaeróbios sem prévio tratamento da drenagem ácida sob diferentes variáveis. Para o reator anaeróbio horizontal de leito fixo (RAHLF), foram analisadas as variáveis relação DQO/\'SO IND.4\'POT.2-\', correção do pH afluente, carga de sulfato aplicada e a recirculação da fase líquida. Os resultados mostraram que a redução da carga de sulfato aplicada foi o fator determinante para os bons resultados de remoção, encontrados ao longo da operação dos reatores (70% de remoção de sulfato e 75% de remoção de DQO). A relação DQO/\'SO IND.4\'POT.2-\' também foi importante e quando utilizada a relação estequiométrica de 0,67, a eficiência de remoção de sulfato atingiu níveis superiores a 70% com pequeno acúmulo de ácido acético no efluente. Para a operação do reator anaeróbio de manta de lodo (UASB), as variáveis analisadas foram o volume da manta de lodo, a relação DQO/\'SO IND.4\'POT.2-\', a carga de sulfato aplicada e a recirculação da fase líquida. Como para o RAHLF, a redução da carga de sulfato aplicada foi essencial para o melhor funcionamento do UASB. A relação DQO/\'SO IND.4\'POT.2-\' de 1,0 promoveu melhora na eficiência do reator, quando comparada à relação estequiométrica e a recirculação no reator só foi positiva quando realizada com água de abastecimento, tendo o reator entrado em colapso quando a recirculação foi realizada com o efluente tratado. / The main objective of this work was to evaluate the sulfate removal from acid mine drainage in two types of anaerobic reactors, one with a granular sludge (UASB) and another with immobilized biomass (HAIB reactor). Previous published studies have showed positive results for the anaerobic treatment of acid mine drainage, however, in most of them, it was applied a pre-treatment operation. This study evaluated the operation of anaerobic reactors without pre-treatment of the acid mine drainage under different parameters. The parameters COD/\'SO IND.4\'POT.2-\' ratio, correction of affluent pH, sulfate loading and recirculation of the liquid phase were tested for horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The results showed that the decrease in the sulfate loading was a determining factor for the successful sulfate removal found throughout the operation of the reactors. The COD/\'SO IND.4\'POT.2-\' ratio was also important and the removal efficiency of sulfate reached levels above 70% with a small accumulation of acetic acid in the effluent when using stoichiometric ratio of 0.67. For the operation of the upflow anaerobic sludge blanket (UASB) reactor, the parameters were the volume of the sludge blanket, the COD/\'SO IND.4\'POT.2-\' ratio, the sulfate loading and the recirculation of the liquid phase. Similarly ti the HAIB reactor, reducing the sulfate load was essential for obtaining better results. The COD/\'SO IND.4\'POT.2-\' ratio of 1.0 showed a improved sulfate removal efficiency for the UASB reactor when compared to stoichiometric ratio at 0.67 ant the recirculation in this reactor was only positive when carried out with tap water. The UASB reactor collapsed when recirculation was carried out whit the treated effluent.

Nenhuma / Esta tese apresenta uma avaliação da qualidade das águas superficiais no entorno de uma instalação minero-industrial para produção de urânio, a Unidade de Tratamento de Minérios de Caldas (UTM-Caldas). O objetivo é verificar se os corpos dágua dessa instalação foram impactados por efluentes provenientes da pilha de rocha estéril n 4 (BF4) e da Bacia de Rejeitos (BR). O principal problema ambiental da UTM-Caldas, atualmente em processo de descomissionamento, é a geração de drenagem ácida de mina (DAM). Para o desenvolvimento do trabalho foram implantadas doze estações de amostragem nas bacias que drenam a área da UTM-Caldas: rio Taquari, córrego da Consulta e ribeirão Soberbo. Duas das estações foram posicionadas respectivamente no interior da Bacia Nestor Figueiredo (BNF), bacia de retenção dos efluentes do BF4, e do tanque de deposição do rádio, denominado D2, para onde vertem os efluentes da BR. O monitoramento se desenvolveu em 2010 e 2011, com a determinação de quarenta e dois parâmetros físico-químicos, biológicos e radioativos. Os dados obtidos foram tratados por diferentes abordagens metodológicas, incluindo a distribuição espacial das medianas das determinações, diagramas hidrogeoquímicos, estudo de isótopos estáveis e do cálculo do background geoquímico, além da aplicação de índices de qualidade das águas. De maior relevância, os resultados mostraram que efluentes provenientes da BNF contribuíram para que os corpos dágua a jusante, principalmente o córrego da Consulta, apresentassem contaminação para flúor, cádmio, urânio, zinco, alumínio, manganês e acidez, assim como foram responsáveis para o enriquecimento em sulfato, cálcio, arsênio, magnésio, 238U, 226Ra, 232Th e 228Ra. Os resultados indicaram que efluentes advindos do D2 causaram um enriquecimento em cálcio, flúor, sulfato e molibdênio nas águas do ribeirão Soberbo. As águas do córrego da Consulta, imediatamente a jusante da BNF, receberam a pior classificação do índice WQI/CCME, ou seja, pobre. / This thesis presents an evaluation of the quality of surface waters in the surroundings of the industrial-mineral facilities for the production of uranium owned by the Caldas Ore Treatment Unit (UTM-Caldas), aiming to verify whether the water bodies downstream the plant, were impacted by effluents from the Waste Rock Pile 4 (BF4), and from the Tailings Dam (BR). The main environmental problem of UTM-Caldas, currently in decommissioning process, is the generation of Acid Mine Drainage (AMD). In order to perform the research, twelve sampling stations were established in the watersheds around UTC: the Soberbo and Consulta creeks, and the Taquari river. One of the stations was located, inside the BNF (retention pond that receives effluents from BF4), and another at D2 (a settling tank for radium, which receives the effluents from BR). A monitoring plan has been developed, comprising four sampling campaigns in 2010 and 2011. It involved the measurement of forty-two physical, chemical, biological and radioactive parameters. The data obtained were processed by different methodological approaches, including the spatial distribution of medians of the recorded results, hydrogeochemical diagrams, stable isotopes measurements and evaluation of the geochemical background, besides the use of indexes for water quality. Of greater relevance, the results indicated that the effluents from the BNF contributed to the contamination, mainly of the Consulta creek, by F-, Cd, U, Zn, Al, Mn, besides increased acidity and enrichment of SO42-, Ca, As, 238U, 226Ra, 232Th, and 228Ra. The results indicated that the effluents discharged at D2 caused the waters of the Soberbo creek to be enriched in Ca, F-, Mo and SO42-. The stretch of the Consulta creek immediately downstream the BNF received the worst classification according with the WQI/CCME Index, i.e. "poor".

A primeira mineração de urânio do Brasil está localizada nas dependências da Unidade de Tratamento de Minérios das Indústrias Nucleares do Brasil. Atualmente, essa área mineradora encontra-se em fase de descomissionamento e a drenagem ácida de mina constitui o principal passivo ambiental, devido ao volume de efluentes radioativos gerados, os quais após tratamento são lançados na represa das Antas (RA). Os resultados indicaram que amostras do efluente in natura e tratado apresentaram maiores concentrações de espécies químicas, sendo consideradas agudamente tóxicas para os dafinídeos, indicando que que o sistema de tratamento realizado pela mineradora foi impróprio e ineficiente. Valores de dureza extremamente elevados indicaram efeito protetor para os dafinídeos, quando maiores concentrações de metais tais como F-, U, Mn e Al foram registradas. O metal Mn apresentou potencial de causar toxicidade para C. silvestrii, CE50 (5,93 mg L-1). Para U, mudanças no pH nos ensaios de D.magna, estiveram associadas a alterações nas concentrações das espécies potencialmente tóxicas UO22+ e UO2OH+. A espécie nativa C. silvestrii mostrou ser muito mais sensível a U, quando comparada a D. magna, de acordo com a CE50 (0,07 e 0,56 mg L-1, respectivamente). / The first uranium mining in Brazil is located on the Ore Treatment Unit of Nuclear Industries of Brazil. Currently, this mining area is in process of decommissioning and the acid mine drainage is the main environmental liability due to the volume of radioactive effluents produced, which after treatment are discharged into the Antas reservoir (AR). The results indicated that samples of the in natura and treated effluent presented higher concentrations of chemical species, being considered acutely toxic to the daphnids, indicating that the treatment carried out by the mining company (UTM/INB) was improper and inefficient. Extremely high hardness values indicated protective effect for the daphnids, when higher concentrations of metals such as F-, U, Mn and Al were recorded. The Mn metal presented potential toxicity for C. silvestrii, EC50 (5.93 mg L-1). For U, changes in pH in the D.magna assays were associated with changes in concentrations of the toxic potentially species UO22+ and UO2OH+. The native species C. silvestrii showed to be much more sensitive to U, than D. magna, according to EC50 (0.07 and 0.56 mg L-1, respectively).

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / Acid rock drainage (ARD) is one of the most severe environmental challenges currently faced by the mining industry worldwide. ARD is formed from the oxidation of sulphide-bearing minerals, particularly pyrite, in the presence of water and oxygen. ARD generation is accelerated by the presence of naturally occurring iron and sulphur-oxidizing micro-organisms, which regenerate leaching agents that facilitate sulphide mineral oxidation. ARD pollution is characterized by a high concentration of metals and sulphates in solution, low pH and a high salt content (salinity) in the environment, contaminating soil and groundwater. In South Africa, ARD is a major challenge in the gold and coal mining industries, where millions of tons of sulphide waste rock and overburden are generated and discarded. Characterization of these waste materials is required to develop an appropriate disposal strategy to minimise the risk of pollution and the generation of ARD. Potential ARD generation prediction from waste rock depends on the precise characterization of ARD potential using Biokinetic tests. Commonly used ARD prediction methods are static and long-term kinetic tests. Static tests provide data for a worst-case scenario focussing on strong acid chemical leaching potential to give an overall acid forming potential of a sample. Such kinetic tests provide data illustrating the rate of the net acid generation capacity of mine waste. However, these tests are capital intensive and time-consuming and fail to provide adequate information on the effect of micro-organisms on the overall net acid generation capacity of mine waste. The Biokinetic test reported herein and developed at the University of Cape Town, focusses on addressing a worst case scenario provided by static tests in a cost-effective manner and reduced time frames provided for by conventional kinetic tests. This test primarily provides relative rates of ARD generation in the presence of micro-organisms within 90 days. However, the Biokinetic test is at the developmental stage and thus far, has not been consistently used for different waste ores to determine a standardised approach. Therefore, the aim of this study was to investigate the effects of microbial consortia and to develop a standardisation approach for the test for ARD formation potential using gold-bearing and copper-bearing waste rock. Additionally, to refine the Semi-continuous Biokinetic test simulation, a flow-through system where there is minimal seepage in the waste deposit, was also developed. The sulphur content of the gold and copper-bearing samples used in this study was between 2.3 and 3.15%, respectively. These waste rock samples were found to be potentially acid- forming. In the Biokinetic test, finely milled waste rock samples were slurrified, inoculated with consortia and cultured under standard bioleaching conditions. Leaching and acidification rates were monitored.

Fanny Creek drains from Island Block opencast coal mine, near Reefton on the West Coast of the South Island of New Zealand, and is impacted by acid mine drainage (AMD). The objectives of this study were to characterise drainage chemistry in Fanny Creek catchment, and to determine optimal passive treatment strategies for Fanny Creek AMD for future pilot or full-scale application. This was undertaken by monthly monitoring in Fanny Creek catchment between February 2008 and January 2009 to collect drainage chemistry and flow data. Laboratory trials of suitable passive AMD treatment systems were conducted and their treatment performance assessed to select and design optimal passive treatment strategies for Fanny Creek AMD. Oxidation of pyrite in Brunner Coal Measure sediments at Island Block mine generates AMD. Fanny Creek originates from a number of AMD seeps on the eastern waste rock slope of Island Block mine. Seeps have low pH (<3.23) and a single detailed metal analysis indicates drainage is enriched with aluminium and iron, and contains elevated concentrations of manganese, copper, nickel, zinc and cadmium relative to applicable water quality criteria such as ANZECC guidelines. Acidity and metal loadings of drainage in the catchment indicates AMD from the northern waste rock slope contributes most of the acidity (~70%) and metal (60%) in Fanny Creek, and acts to re-dissolve additional metals upon mixing with drainage from other slopes. The most suitable location for a passive AMD treatment system in Fanny Creek catchment is on the Waitahu Valley floor, near monitoring site R12, because this allows for sediment removal prior to a treatment system. Fanny Creek AMD at site R12 was characterized in detail because this data assists with selection and design of passive AMD treatment systems. Fanny Creek at site R12 contains on average 6.0 mg/L aluminium, 1.3 mg/L iron, 3.1 mg/L manganese, 0.49 mg/L zinc, 0.14 mg/L nickel, 0.0071 mg/L copper and 0.00048 mg/L cadmium. Average pH at site R12 was 3.95, calculated acidity averaged 42.7 mg CaCO₃/L, and flow rate ranged from 1.5 L/s to about 30 L/s. Acidity and metal generation from Island Block mine increases linearly with flow in the catchment, and therefore Fanny Creek drainage chemistry is not significantly affected by rainfall dilution. Natural attenuation of AMD occurs by addition of un-impacted alkaline drainage from Greenland Group basement rocks, wetland ecosystem processes, and geochemical reactions along Fanny Creek that decrease acidity and metal concentrations before AMD discharges into the Waitahu River. During low flow conditions (summer months), surface flow of AMD into the Waitahu River does not occur because of subsurface flow loss. Three suitable passive AMD treatment options for Fanny Creek AMD were selected and trialed at ‘bench top’ scale in a laboratory. These included a sulfate reducing bioreactor (SRBR), a limestone leaching bed (LLB), and an open limestone channel (OLC). The potential to mix Waitahu River water with Fanny Creek to neutralize AMD was also investigated. Fanny Creek AMD was employed for laboratory trials, and influent flow rates into SRBR, LLB and OLC systems were regulated to assess performance at different hydraulic retention times (HRT). Optimal HRTs for future treatment system designs were determined from effective AMD treatment thresholds, and include 51 hours, 5 hours and 15 hours for SRBR, LLB and OLC systems, respectively. To determine optimal treatment options for Fanny Creek AMD the effectiveness of each trial option was compared to applicable water quality criteria, and scale up implications of treatment options was assessed. The SRBR system had most effective AMD treatment, with water quality criteria achieved for metals, greatest alkalinity generation, and highest pH increase. However, a full scale SRBR system has significant size requirements, and long term treatment performance may be limited. The LLB system decreased metals to below, or just slightly above criteria for all metals, and has significantly smaller size requirements compared to a SRBR system. The OLC system was least effective, with effluent above water quality criteria for all metals except iron, and with lowest alkalinity generation. The Waitahu River is capable of neutralizing AMD because it is slightly alkaline. The flow volume of river water required for neutralization is between 65 L/s and 140L/s, which can be gravity fed to mix with Fanny Creek. These results indicate that either a LLB treatment system or the Waitahu River Mixing option are the optimal passive treatment strategies for Fanny Creek AMD. On site pilot scale testing of SRBR and LLB systems, and the Waitahu River Mixing option is recommended because of AMD treatment uncertainty, and to more accurately select and design full scale passive treatment strategies.