No description available.

Waste rocks (WRs) from coal mining and fly ash (FA) from coal combustion were studied to determine the potential of the WRs to generate AMD, FAs to neutralise it and estimate their impacts on environment. The ultimate goal was to develop a methodology based on co-disposal to mitigate the environmental problems associated to both wastes. Two methods for co-disposal were tested: i) Mixing WRs and FAs and ii) covering WRs with FAs. WRs were sampled from the Lakhra coal mines in Pakistan (PK), which has an estimated coal reserves of 1.3 Btonne, varying from lignite to sub-bituminous quality. The FA was sampled from a power plant utilising coal from Lakhra coal mines and is situated in close vicinity (15km) of the mine site. For comparative purposes a bituminous FA from Finland (FI) and biomass FA from Sweden (SE) were also characterised. The WRs and FA samples were characterised by mineralogical and geochemical methods. Besides organic material (coal traces), quartz, pyrite, kaolinite, hematite, gypsum and traces of calcite, lime, malladerite, spangolite, franklinite and birnessite were identified in WRs by XRD. The major elements Si, Al, Ca and Fe were in the range (wt. %) of 8 – 12, 6 – 9, 0.3 – 3 and 1 – 10, respectively, with high S concentrations (1.94 – 11.33 wt. %) in WRs. The AMD potential of WRs ranged from -70 to -492 kg CaCO3 tonne-1. All FAs contained quartz, with iron oxide, anhydrite and magnesioferrite in PK, mullite and lime in FI and calcite and anorthite in SE. The Ca content in SE was 6 and 8 times higher compared to PK and FI, respectively. FAs were enriched in As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn compared to continental crust. The acid neutralising potential of PK was equivalent to 20 kg CaCO3 tonne-1 compared to 275 kg CaCO3 tonne-1 (SE) and 25 kg CaCO3 tonne-1 (FI). During the period of 192 days in weathering cell experiments (WCE), the pH of leachates from most acidic WRs was maintained from 1 to 2.5, whereas, the less acidic WRs produced leachates of mildly acidic (2.7) to neutral (7.3) pH. The leachates from very acidic WRs ranged in the concentrations of Fe, SO24− and Al from mg L-1 to g L-1. The samples were subjected to column leaching experiments (CLE) in which mixture (FA:WR; 1:3) and cover (FA:WR; 1:5) cases were mimicked (with 10mm particle size) and effects of particle size (2, 5 and 10mm) on element leaching were studied. Despite having the lowest acid-neutralisation potential compared to FI and SE, co-disposal of PKFA as mixture readily provides acid buffering minerals, resulting in better start-up pH conditions and leachate quality. However, acidity produced by secondary mineralisation contributes towards the acidification of the system, causing stabilisation of pH at around 4.5−5. Secondary mineralisation (especially Fe- and Al-mineral precipitation) also removes toxic elements such as As, Pb, Cu, Zn, Cd, Co, Ni and Mn, and these secondary minerals can also buffer acidity when the pH tends to be acidic. In contrast, the pH of the leachates from the PKFA cover scenario gradually increased from strongly acidic to mildly acidic and circumneutral along with decrease in EC and elemental leaching in different WRs. Gradually increasing pH can be attributed to the cover effect, which reduces oxygen ingress, thus sulphide oxidation, causing pH to elevate. Due to the fact that pH~4–5 is sufficient for secondary Fe- and Al-mineral precipitation which also removes toxic elements (such as Cd, Co, Cu, Zn and Ni) by adsorption and/or co-precipitation, the FA cover performs well enough to achieve that pH until the conclusion of the CLE. However, due to the slower reactivity of the buffering system (additional to the initial flush-out), leaching in the beginning could not be restricted. The co-disposal of FA as cover and/or mixture possesses potential for neutralisation of AMD and improving leachate quality significantly. Particle size of the WRs affected the leaching of the sulphide related elements (such as Fe, S, Zn, Co, Cr, Cu, Mn and Ni) in CLE and WCE. Experiments with ≤1mm particle size constantly produced acidic and metal laden leachates. Co-disposal of FA and WRs as cover and mixture need to be investigated on pilot-scales before full-scale application.

No description available.

Thesis (MSc)--Stellenbosch University, 1997. / ENGLISH ABSTRACT: The activity of iron-oxidizing bacteria, for example, Thiobacillut. ferrooxidans, in the outer layers of coal waste dumps results in the oxidation of pyrite with the formation of large volumes of acid mine drainage. The process requires atmospheric oxygen and moisture. Acid mine drainage may possibly be controlled by creating unfavourable environmental conditions in dumps for the iron-oxidizing bacteria. The present research investigated the possibility of inhibiting these bacteria and consequently acid formation in coal waste dumps by means of different dump construction techniques. Physical and chemical conditions, acid formation and populations of four groups of bacteria which might produce acid were studied in the outer layers of ten differently constructed pilot scale coal waste dumps at the Kilbarchan Mine near Newcastle, Kwazulu-Natal, from September 1993 to July 1995. Dump covers consisting of a 30-cm or 70-cm layer of Estcourt soil of low permeability covered with 70 cm or 30 cm, respectively, of more permeable Avalon soil produced anaerobic conditions in the dumps throughout most of the 22 months of the test period, as did a cover of 70 cm compacted plus 30 cm uncompacted Avalon soil alone. An uncoMpacted 30-cm or compacted 50- cm Avalon soil cover proved ineffective in causing prolonged anaerobic conditions. Uncovered dumps showed only slight reduction of oxygen in the coal waste after heavy rains. Pockets of acidity were detected on several occasions in the coal waste below the 50-cm Avalon soil layer from the time of construction and progressively increasing acidity in the uncovered dumps and the waste below the 30-cm Avalon soil cover. Iron-oxidizing bacterial populations of the T. ferrooxidans type have tended to be higher in the uncovered dumps and Avalon soil-covered dumps showing acidification than in the non-acidified dumps covered with 1 m of Avalon soil or Avalon and Estcourt soil. Associated populations of iron-oxidizing bacteria of the Metallogenium type, acidophilic and non-acidophilic thiosulphate-oxidizing bacteria were generally low in the coal waste of the dumps. Thus, five of the soil covers, all with a thickness of 1 m, but not covers with a thickness of 0.5 m or less, proved effective for almost 2 years in inhibiting the diffusion of oxygen to the underlying coal waste in the pilot scale dumps and also appeared to suppress the populations of iron-oxidizing bacteria believed to be implicated in acid formation in the coal waste. These results suggest that coal waste dumps in South Africa should be covered with soil layers of 0.5-1.0 m thick to prevent the generation of acid mine drainage. / AFRIKAANSE OPSOMMING: Die aktiwiteit van ysteroksiderende bakteriee soos Thiobacillus ferrooxidans, in die buitenste lae van steenkoolafvalhope, veroorsaak die oksidasie van piriet met die gevolg dat groot volumes suur mynafloopwater gevorm word. Hierdie proses benodig suurstof en vog. Suur mynafloopwater kan moontlik beheer word deur 'n situasie te skep waar die toestande in die hope ongunstig is vir die ysteroksiderende bakteriee. Die huidige navorsing het die moontlikheid ondersoek om hierdie bakteriee te inhibeer deur verskillende afvalhoopontwerpe op die proef te stel en sodoende suurvorming in steenkoolmynhope te beperk. Die fisiese en chemies kondisies, suurvorming en populasies van vier verskillende bakterie-groepe wat dalk by suurvorming betrokke is, is vanaf September 1993 tot Julie 1995 bestudeer in die buitenste lae van tien verskillend gekonstrueerde loodsskaalafvalhope by die Kilbarchan myn naby Newcastle in KwaZulu-Natal. Afvalhoopbedekkings bestaande uit 'n 30-cm of 70-cm Estcourt grond met 'n lae permeabiliteit bedek met'n 70-cm of 30-cm laag van meer deurlaatbare Avalon grond het anaerobe kondisies veroorsaak. Ongekompakteerde 30-cm en gekompakteerde 50-cm Avalon grondlae het egter nie bestendige anaerobe kondisies in die hope veroorsaak nie. Die onbedekte hope het aerobics gebly met slegs effense dalings van suurstofkonsentrasies gedurende en na swaar reens. Geisoleerde monsters uit die steenkoolafval onder die 50-cm Avalon grondlaag het vanaf die begin van die toetsperiode tekens van suurvorming getoon. Die onbedekte steenkoolafval en die van die sel met 'n 30-cm Avalon grondlaag het met verloop van tyd al hoe meer suur geword. Die ysteroksiderende bakterie-populasies van die T. ferrooxidans tipe het geblyk om in die onbedekte en Avalon grondbedekte hope wat tekens van suurvorming getoon het hoer te wees as in die hope wat met 'n 1-m laag Avalon grond of Avalon en Estcourt grond bedek is en geen tekens van suurvorming getoon het nie. Ysteroksiderende bakteriepopulasies van die Metallogenium tipe, nieasidofiele en asidofiele tiosulfaatoksiderende populasies was oor die algemeen laag in die steenkoolafvalhope. Vyf van die grondlae wat alma! 1 m dik was het dus geblyk om effektief te wees in die bekamping van die infiltrasie van suurstof na die onderliggende steenkoolafval in die loodskaalhope. Dit lyk asof daardie lae die ysteroksiderende populasies betrokke by suurvorming onderdruk het. Die 0.5-m grondbedekking het egter nie so 'n sterk onderdrukkende effek op die suurstofinfiltrasie of die bakteriepopulasie gehad nie. Na aanleiding van hierdie resultate blyk dit dat steenkoolafvalhope in Suid-Afrika met minstens 0.5 tot 1..0 m grond bedek moet word om effektief die probleem van suur mynafloopwater te bekamp.

Thesis (MSc)--Stellenbosch University, 1998. / One copy microfiche. / ENGLISH ABSTRACT: The biologically catalysed oxidation of pyrite in the outer layers of coal waste dumps leads to the formation of acid mine drainage. The oxidation of pyrite to ferric iron and sulphate is a complex process involving various abiotic and biologically catalysed reactions. Pyrite is abiotically oxidized by ferric iron, with the formation of thiosulphate and ferrous iron. Thiosulphate decomposes to form various inorganic sulphur compounds. Bacterial catalysis of pyrite oxidation is achieved by iron-oxidizing bacteria oxidizing ferrous iron to ferric iron. Bacteria that oxidize sulphur compounds assist the catalysis by oxidizing thiosulphate and its decomposition products. Heterotrophic organisms may play a role by consuming organic substances inhibitory to the lithotrophic bacteria. Abiotic ecological factors, acid formation and populations of iron-oxidizing bacterial groups were studied in 10 differently constructed pilot scale coal waste dumps, as the second phase of a study which started in September 1993. Gas samples were withdrawn weekly from coal waste through permanently buried stainless steel probes, for analysis in the field using a portable oxygen/carbon dioxide meter. Samples of coal waste were extracted by auger for analysis of moisture, pH and microbial populations. The analyses of oxygen and pH can be recommended for the routine monitoring of rehabilitated waste dumps. Covers of Avalon soil 0.3 or 0.5 m thick, were not adequate to prevent acidification. Coal waste covered with 0.7 m compacted beneath 0.3 m uncompacted Avalon soil, showed a slow pH decline, but reached approximately pH 3 in 1997. Covers of compacted Estcourt soil beneath tmcompacted Avalon soil to a cover depth of 1 m were effective in preventing acidification and generally kept the coal waste anaerobic. However, all covers developed cracks during drought conditions in 1995, allowing aeration. Low pH of some samples from these dumps during 1995/1996 may have indicated the start of acidification. Bacteria oxidizing high concentrations of ferrous iron and considered to be Thiobacillus ferrooxidans, were monitored routinely, but may not have been the dominant iron-oxidizer, as population counts using media with a lower ferrous iron concentration were higher. The majority of the latter organisms could also not oxidize sulphur, hence were not T. ferrooxidans. The populations of the high ferrous iron-oxidizing bacteria were affected by pH, tending to be high in acidified and low in non-acidified coal waste. Investigations of microbial populations forming iron-oxidizing consortia in enrichment cultures from coal waste and acid drainage samples showed the presence of T. ferrooxidans, the heterotrophic bacterial genus Acidiphilium, fungi of the genus Penicillium, unidentified filamentous fungi, including Cladophialophora-like morphological types, and a yeast of the genus Dipodascus. In interaction studies, the Penicillium isolate had an inhibitory effect on T. ferrooxidans (subjected to organic compound stress), but the Cladophialophora-like fungi reduced inhibition by organics. Fungi have not previously been studied in detail as components of iron-oxidizing consortia, but the bacterial isolations agree with those elsewhere, indicating that appropriate conclusions from acid mine drainage research in other parts of the world can be applied in KwaZulu-Natal. / AFRIKAANSE OPSOMMING: Die biologies gekataliseerde oksidasie van piriet in die buitenste lae van steenkoolafvalhope lei tot die vorming van suur mynafloopwater. Die oksidasie van piriet tot ferri-yster en sulfaat is 'n komplekse proses wat abiotiese en biologies gekataliseerde reaksies insluit. Piriet word abioties deur ferri-yster geoksideer, met die vrystelling van tiosulfaat en ferro-yster. Tiosulfaat verval om verskeie anorganiese swawelverbindings te vorm. Bakteriese katalise van pirietoksidasie word deur ysteroksiderende bakteriee wat ferro-yster na ferri-yster oksideer, bewerkstellig. Bakteriee wat swawelverbindings oksideer maak 'n bydrae tot die katalise deur tiosulfaat en vervalprodukte daarvan te oksideer. Heterotrofe organismes mag ook 'n rol speel deur organiese verbindings wat die litotrofe bakteriee mag inhibeer, te verbruik. Abiotiese ekologiese faktore, suurvorming en bevolkings ysteroksiderende bakteriee is in 10 verskillend gekonstrueerde loodsskaal steenkoolafvalhope bestudeer, as die tweede fase van 'n studie wat in September 1993 begin het. Gas monsters is weekliks uit die steenkoolafval onttrek deur vlekvrye staal peilers wat permanent daarin begrawe is, en met behulp van 'n draagbare suurstoflkoolstofdioksiedanaliseerder in die veld ontleed. Monsters van die steenkoolafval is met behulp van 'n kleiboor vir die analise van vog, pH en mikrobepopulasies geneem. Die analise van suurstof en pH kan aanbeveel word vir die roetiene monitering van gerehabiliteerde afvalhope. Bedekkings van 0.3 of 0.5 m Avalongrond was nie voldoende om suurvorming te verhoed nie. Steenkoolafval wat met 0.7 m gekompakteerde en 0.3 m ongekompakteerde Avalongrond bedek is, het 'n stadige pH-daling getoon, maar het in 1997 ongeveer pH 3 bereik. Bedekkings van gekompakteerde Estcourtgrond onder ongekompakteerde A valongrond met 'n totale dikte van 1 m, was effektief in die voorkoming van suurvorming. Hulle het oor die algemeen die steenkoolafval anaerobies gehou, maar aile bedekings het tydens die droogte in 1995 krake ontwikkel, wat suurstof laat binnedring het. 'n Lae pH gedurende 1995/1996 by sommige monsters uit hierdie hope mag die begin van suurvorming aangedui het. Bakteriee wat hoe konsentrasies ferro-yster oksideer en wat as Thiobacillus ferrooxidans beskou is, was moontlik nie die dominante ysteroksideerder nie, aangesien bevolkingstellings waar 'n medium met 'n laer konsentrasie ferro-yster gebruik is, hoer bevolkings getoon het. Die meerderheid van laasgenoemde organismes kon ook nie swawel benut nie en dus nie T. ferrooxidans was nie. Die bevolkings van die hoe ferro-ysteroksiderende bakteriee is deur pH beInvloed, met 'n geneigdheid tot hoe bevolkings in suur en lae bevolkings in minder suur steenkoolafval. Ondersoeke na die rnilcrobebevollcings wat in ysteroksiderende konsortia in verryldngslculture vanaf steenkoolafval- en suur mynafloopwatermonsters voorgekom het, het die teenwoordigheid van 7'. ferrooxidans, die heterotrofe balcteriegenus Acidiphilium, fungi van die genus Penicillium, ongeIdentifiseerde fungi, insluitend Cladophialophora-agtige tipes en 'n gis van die genus Dipodascus aangetoon. By interaksiestudies het die Penicillium-isolaat 'n inhiberende effek op T ferrooxidans (onderworpe aan organiese verbindingstres) gehad, maar die Cladophialophora-agtige fungi het die inhibisie deur organiese verbindings verminder. Fungi is nog the in detail as komponente van ysteroksiderende konsortia bestudeer the, maar die isolasies van bakteried stem saam met die van elders wat aandui dat toepaslike gevolgtreldcings ten opsigte van suur mynafloopwatemavorsing vanaf ander dele van die wereld ook in KwaZulu-Natal toegepas kan word.

MESMEG / Department of Mining and Environmental Geology / The Mushithe coal occurrence is situated approximately 16 km west of the Tshikondeni coal mine in the Tshipise-Pafuri sub-basin of the Soutpansberg coalfield in South Africa. The Soutpansberg Coalfield has received comparatively less attention compared to other more notable South African coalfields. There is as a consequence very limited information in the public domain applicable to the geology as well as quality of coal in this coalfield, as a result there is no known study focused exclusively on the Mushithe coal occurrence. The aim of the study was to conduct detailed geological mapping of the Mushithe Deposit so as to ascertain the geological environment and petrological characteristics of rocks within the area. Further work involved coal sampling and analysis in order to establish coal quality and its physical and chemical characteristics. Samples were collected using geological field mapping and channel sampling. Nine coal samples were collected from the coalbed and host rock, exposed along the Mbodi River, during geological field mapping using channel sampling. Furthermore, 92 rock samples were collected during geological field mapping of which 10 representative samples were selected for further analysis. X-ray fluorescence spectrometry was conducted on all selected samples. Proximate analysis and ultimate analyses, and calorimetry tests were undertaken on coal samples. Three samples were selected based on calorific value for maceral identification, mineral analyses and vitrinite reflectance using petrographic study. Detailed geological mapping of the area around the Mushithe coal occurrence showed the geological setting of coal in this area. The following lithologies were identified in the study area: sandstone, mudstone, ironstone, calcrete, shale, quartzite, quartz vein with a general strike direction to the north-east. The host rocks including coal were intruded by dolerite dykes and this resulted in the devolatilization of coal. The current study concluded that the Mushithe coal was formed in a wet swampy environment. This has been confirmed based on tissue preservation index (1.69) and gelification index (2.35). Coal rank ranged from bituminous Rank C- B according to United Nations Economic Commission for Europe Coal Classification (UNECE) and samples were characterised by high ash (27.90%), high moisture (10.47%) and low sulphur (0.24%). Furthermore, coal was graded below grade D based on classification for use by ESKOM which consider any calorific value below 24.5 MJ/kg to be in this category. The coal is vitrinite rich (77.75 vol%) and low in Inertinite (22.25 vol%) and devoid of Liptinite and pseudovitrinite, thus it is of good coking quality. Geochemical analysis revealed that the coal was enriched in TiO2 and Fe2O3 which was corroborated by the mineral matter which was mostly clay and pyrite. Comparatively, coal quality analysis revealed the calorific value of 14.26 MJ/kg and vitrinite reflectance between 0.94 %ROV to 1 %ROV which was less than that of the Tshikondeni Deposit but greater than that at Waterberg coalfield. The study recommends further detailed exploration of coal in the area, applying such techniques such as geophysical exploration and borehole drilling leading to resource evaluation. Further studies are recommended to provide a better interpretation of the depositional environment of coal at Mushithe as well as the effect of devolatilaziton by a dolerite dyke. / NRF

No description available.

Coal seams are commonly associated with poor quality water that requires treatment. Water treatment can be very expensive and can severely affect the profitability of mining projects. This study investigated the potential cultivation of Arthrospira maxima (Spirulina) in coal seam water to beneficiate coal seam water in order to effectively offset the water treatment cost. The study was conducted in Northern South Africa and formed part of a larger Coal Seam Water Beneficiation Project (CSWBP). The study consisted of laboratory based Flask Studies and outdoor High Rate Algal Pond Studies. The Flask Studies that were carried out in the on-site field laboratory, found that the coal seam water could provide a suitable medium for Spirulina cultivation. In addition, it was found that the optimal pH for the selected strain ranged between 9 - 10.5 and that the addition of excess iron, up to 100 times the concentration found in defined growth media such as Schlösser’s, to the culture media could enhance productivity. The High Rate Algal Pond Studies (HRAP) were carried out over a period of 18 months. The studies showed that the coal seam water at the CSWBP is a valuable resource that can reduce media costs by 50% without affecting productivity. In a study encompassing 334 days it was shown that heating the culture through plate heat exchangers would result in a significant increase in productivity and a heated productivity of 19.86 g/m2/day was recorded. An unheated productivity of 14.11 g/m2/day was recorded. Therefore, it was found that it would be economically feasible to beneficiate coal seam water found at the CSWBP through the cultivation of Arthrospira maxima (Spirulina). / Environmental Sciences / M. Sc. (Environmental Science)

Coal seams are commonly associated with poor quality water that requires treatment. Water treatment can be very expensive and can severely affect the profitability of mining projects. This study investigated the potential cultivation of Arthrospira maxima (Spirulina) in coal seam water to beneficiate coal seam water in order to effectively offset the water treatment cost. The study was conducted in Northern South Africa and formed part of a larger Coal Seam Water Beneficiation Project (CSWBP). The study consisted of laboratory based Flask Studies and outdoor High Rate Algal Pond Studies. The Flask Studies that were carried out in the on-site field laboratory, found that the coal seam water could provide a suitable medium for Spirulina cultivation. In addition, it was found that the optimal pH for the selected strain ranged between 9 - 10.5 and that the addition of excess iron, up to 100 times the concentration found in defined growth media such as Schlösser’s, to the culture media could enhance productivity. The High Rate Algal Pond Studies (HRAP) were carried out over a period of 18 months. The studies showed that the coal seam water at the CSWBP is a valuable resource that can reduce media costs by 50% without affecting productivity. In a study encompassing 334 days it was shown that heating the culture through plate heat exchangers would result in a significant increase in productivity and a heated productivity of 19.86 g/m2/day was recorded. An unheated productivity of 14.11 g/m2/day was recorded. Therefore, it was found that it would be economically feasible to beneficiate coal seam water found at the CSWBP through the cultivation of Arthrospira maxima (Spirulina). / Environmental Sciences / M. Sc. (Environmental Science)