Magister Scientiae - MSc / The waste products acid mine drainage formed during coal mining and fly ash from coal burning power generation, pose substantial environmental and economic problems for South Africa. Eskom has developed a remediation system employing alkaline fly ash to neutralize and precipitate heavy metals from toxic acidic acid mine drainage streams. The aim of this study was to assess the microbial diversity in and microbial impact on this remediation system. / South Africa

This thesis investigates the development of regional drainage patterns within intra-continental rift basins using remote sensing data, field studies and numerical models. By examining modern-day extensional settings, such as the Basin and Range, USA, and the East African Rift System (EARS), this study elucidates the controls upon regional source-to-sink systems and assesses the findings in relation to existing, conceptual tectono-stratigraphic and drainage models. Rift basins are generally well studied and facies models well established. However, there is a tendency to overlook the regional perspective. Many drainage evolution studies and tectono-stratigraphic models focus upon the development of individual basin-bounding faults and half-grabens, often overlooking the influence of regional-scale drainage evolution upon landscape and stratigraphic development. On a regional scale, extensional basins are segmented into numerous sub-basins, which: (i) exist at different elevations; (ii) subside at different rates; (iii) vary in their degree of fluvial connectivity; and, (iv) may experience significant shifts between erosional and depositional regimes as drainage networks evolve. Through observations of the Basin and Range, and three-dimensional numerical modelling, it is shown how sub-basins with identical tectonic and climatic boundary conditions can exhibit vastly different stratigraphic fills depending on the degree of fluvial connectivity and their relationship to adjacent sub-basins. In addition, drainage integration is recognised as an overlooked, yet important process in the source-to-sink evolution of rift basins. Drainage integration between sub-basins of varying elevations is shown to cause widespread erosion and sediment bypass in the upstream basin, while contemporaneously increasing sediment supply to the downstream basin. A case study of the Tecopa Basin shows drainage integration as a powerful driver of base level fall and landscape transience in the absence of significant tectonic or eustatic controls. The differential gradients created by base level fall cause further upstream drainage rearrangements. To understand the evolution of regional hinterland drainages, two rift segments of varying maturity are compared. The Okavango Rift Zone represents a rift initiation phase segment while the Albertine Rift represents a rift climax phase segment. Through analysis of the contributing drainage patterns a model is proposed where early rift drainage is dominated by antecedent directions, with large, low relief, low slope catchments. As rifts mature catchments increase in relief and slope but reduce in asymmetry as the influence of antecedent drainage direction is reduced via tectonic tilting, drainage reversals and ponding. The thesis concludes that current tectono-stratigraphic models of sub-aerial rift settings commonly overlook the role of inter-basin erosion, under-appreciate the influence of antecedent drainage direction in hinterland input, and over-emphasise the role of axial rivers. Future tectono-stratigraphic models should acknowledge distinctions based upon the degree of fluvial connectivity (isolated or integrated sub-basins) and the regional position relative to adjacent sub-basins (upstream and terminal and sub-basins).

Acid mine drainage is a major environmental pollution concern associated with the mining of sulphide-containing ore bodies. Both physicochemical and biological options have been investigated for the treatment of acid mine drainage with recent interest in biological processes targeting low-cost and passive treatment applications. All acid mine drainage biological treatment processes are based to some extent on the activity of sulphate reducing bacteria, and their ability to reduce sulphate to sulphide in the presence of a range of carbon and electron donor sources. A portion of the sulphide produced may be consumed in the precipitation of heavy metals present in the mine drainage. Residual sulphide must be removed, not only due to its toxicity, but especially to prevent its reoxidation to sulphate where salinity reduction is a target of the treatment process. The partial oxidation of sulphide to elemental sulphur is an option that has received considerable attention and both physicochemical and biological options have been investigated. Biological processes have substantial potential cost advantages and run at ambient temperatures and pressures. However, the oxidation of sulphide to elemental sulphur is poised over a narrow redox range and process control to maintain optimum conditions remains a serious problem. In addition little has been reported in the literature on process control of sulphide oxidation to elemental sulphur, in the heterotrophic conditions prevailing in the reaction environment following sulphate reduction. This study undertook an investigation of biological sulphide oxidation under heterotrophic conditions in order to establish the effect of organic compounds on biological sulphide oxidation, and to determine whether the presence of organics, and associated heterotrophic oxygen consumption, may be manipulated to maintain the defined redox conditions required for the production of elemental sulphur. Biological sulphide oxidation under heterotrophic conditions was investigated in a series of flask experiments. Based on these results three different reactor configurations, a Fixed-Film Trickle Filter Reactor, Submerged Fixed-Film Reactor and a Silicone Tubular Reactor were used to investigate sulphur production. The flask studies indicated that organics, and associated heterotrophic metabolism in the presence of excess oxygen in the sulphide oxidation reaction environment, did contribute to the poising of redox conditions and thereby enabling the production of elemental sulphur. While the Fixed-Film Trickle Filter Reactor was found to be redox unstable, probably due to excess oxygen ingress to the system, a reduced oxygen challenge in the Submerged Fixed-Film Reactor configuration was found to be more successful for production of elemental sulphur. However, due to the production of a predominantly filamentous sulphur producing microbial population, recovery of sulphur from the column was intermittent and unpredictable. Extended residence times for produced sulphur on the column increased the likelihood for its eventual oxidation to sulphate. The Silicone Tubular Reactor was found to support a vigorous sulphide oxidising biofilm and produced elemental sulphur effectively. Electron microscopic studies showed that this occurred as both biologically produced sulphur and, probably mainly, as crystalline sulphur in the ortho-rhomic form. Given the linear extension of the sulphur production reaction environment it is was possible to investigate the sequence of the reaction mechanism in grater detail than is possible in mixed systems. Based on these findings a model explaining sulphur production under heterotrophic conditions has been proposed and is presented. The commercial implications of the development have also been noted.

Due to environmental pollution caused by acid mine drainage (AMD), the Department of Water Affairs has developed a National Water Bill for managing and controlling the water environment to prevent AMD pollution. The application of sulphate reducing bacteria have been demonstrated for the treatment of AMD. However, the scale-up application of this technology ultimately depends on the cost and availability of a carbon source. This study evaluated the use of sewage sludge to provide a carbon source for sulphate reduction in synthetic drainage wastewaters. The demonstration of this process in a laboratory-scale reactor proved that sewage sludge could provide a useful model and viable carbon source for evaluation of sulphate reduction as a process for treating AMD. Since sewage sludge is a complex carbon source, hydrolysis reactions controlling the anaerobic digestion of particulate substrate from this medium were optimized by evaluating the effect of pH on hydrolysis. Controlled and uncontrolled pH studies were conducted using a three stage mixed anaerobic reactor. Analysis of the degradation behaviour of the three important organic classes (carbohydrate, proteins and lipids) revealed that each class followed an indvidual trend with respect to pH changes. In addition, the solubilization of organic particulate carbon was also shown to be a function of pH. The hydrolysis pattern of organic substrate and COD solublization was induced at pH 6.5 rather than at high pH values (7.5 and 8.5). The biodegradation activity of sewage sludge was characterized by the API-ZYM1N test system to provide rapid semiquantitative information on the activity of hydrolytic enzymes associated with the degradation of carbohydrates, lipids, proteins and nucleic acids. A wide range of enzyme activities with phosphatases, aminopeptidases, and glucosyl hydralases dominating were displayed. The pattern of substrate hydrolysis correlated to the degradation efficiency of each organic class as a function of pH. The evaluation of scale-up application for sulphate reduction utilizing sewage sludge as a carbon source demonstrated that large water volume flows could possibly be treated with this cost-effective technology. Generation of alkalinity and sulphide in this medium was shown to be successful in the removal of heavy metals by precipitation. The use of this technology coupled to reduced cost involved showed that biological sulphate reduction utilizing hydrolysates of complex organic particulate from sewage sludge ss a carbon source has a potential scale-up application for the treatment of AMD.

No description available.

This study presents a geochemical characterization of stream waters draining the sedimentary exhalative (SEDEX) Tom and Jason Pb-Zn deposits and surroundings in the MacMillan Pass, Yukon. Streams sampled have wide ranging pH values of 3 to 8.2. Dissolved metal concentrations vary widely with water source and pH. Of note, streams draining the Tom and Jason deposits are acidic and neutral respectively, which greatly affects metal solubility. The Tom Deposit drainage is extremely high in dissolved and fine sediment fraction lead, as well as dissolved zinc. Neutral streams draining the Jason deposit have less dramatic metal concentrations, but do show elevated dissolved zinc and fine sediment fraction lead concentrations. Modelling using the thermodynamic equilibrium program PHREEQC and XRD analysis indicate that ferricrete hardpans underlying acidic drainages are formed where drainage water is saturated with respect to schwertmannite. Ferrihydrite is formed where the rapid mixing of waters increases the pH rapidly. An aluminium oxy-hydroxide, likely gibbsite, precipitates where pH levels exceed 4.5, however it appears to dissolve with decreasing pH. This study looks at dissolved, suspended and fine fraction sediments to provide a more complete view of metal movement under various conditions which may be useful to both exploration and environmental fields.

Water table control by subsurface drainage has been shown to affect leaching losses of nitrate-nitrogen: a concern both for economic use of fertilizer, and for maintenance of water quality. The effect of water table height on leaching of NO₃⁻-N was investigated in this study in nineteen 15cm x 100cm undisturbed cores of silty clay loam. The experiment simulated fertilization followed by rainfall, then rapid water table rise and fall, under conditions similiar to those experienced in the early spring in the Lower Fraser Valley. In the first part of the experiment, a concentrated solution of KNO₃ and KG (equivalent to 35 kg/ha of N and 22 kg/ha of Cl) was applied to the columns, followed by intermittent leaching with distilled water. Leachate from two depths in each column was collected before and after a period of static water table, and analyzed for NO₃⁻, No₂⁻, NH₄⁺, and Cl⁻. This procedure was repeated without nutrient addition in the second part of the experiment. Chloride was used an inert tracer to follow anion movement and retention within the columns. There was no significant difference in the leachate NO₃⁻ concentration or leachate N/CI ratio from any of the four water table heights tested (15, 35, 55, and 75 cm above drain depth). The NO₃⁻ concentrations and N/CI ratios decreased with depth in the soil columns, indicating removal of N from the percolating soil solution, either by denitrification or immobilization. The variability in leachate concentrations among all columns was very high (eg. for a typical sample time, NO₃⁻-N ranged from 0.01 to 15.72 mg/L, and Cl⁻ ranged from 4.8 to 14.5 mg/L), as was the variability in constant head satiated hydraulic conductivities (range: 1 to 1468 cm/day; CV = 181%), and drainable porosity (range: 2.7 to 10.4%; CV = 39%). Cross sections of columns leached with 1% methylene blue solution did not reveal differences in patterns of water transmission between low and high conductivity columns. Indications were that penetration of dye was greater in columns with higher conductivities, and that preferential flow occurred in all columns examined. Leachate concentrations and N/CI ratios correlated significantly with hydraulic conductivity: Spearman's correlation coefficients were always > 0.8 for samples obtained from the bottom of the columns. However, even when the conductivity was included as a covariate in an analysis of covariance, there was no significant effect of water table height on nitrate leaching. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

<p><a>Subsurface tile drainage is a commonly used practice to lower the water table in poorly drained soils, and is often done to improve soil conditions for agricultural operations. Tile drainage has been shown to increase cash crop yield, allow for more timely field operations, and reduce erosion.</a> However, few studies have evaluated the potential long-term changes in soil physical and chemical properties as a result of subsurface tile drainage. This study was conducted on a naturally poorly drained Clermont silt loam soil located at the Southeast Purdue Ag Center near Butlerville Indiana. The intent of this study was to characterize possible evolution of soil physical and chemical properties after 35 years of subsurface drainage. <a>The field site was established in the spring of 1983 with tile drains installed in 2 blocks with tile spacings of 5, 10, 20, and 40m, with the 40-m spacing used as the undrained control</a>. Soil samples were collected in May of 2018 to a depth of 1 meter and were analyzed for carbon and nitrogen content, aggregate stability, and fertility at depth increments of 0-5, 5-15, 15-30, 30-50, 50-75 and 75-100cm. In-field measurements were also taken in May of 2018 for vane shear resistance and in May of 2019 for cone penetration resistance. Total carbon content was found to be significantly higher in the 5-m tile spacing than the 40-m tile spacing in the 0-5cm and 5-15cm depths, with the 10-m and 20-m tile spacings being intermediate. Conversely, in the 75-100cm depth the inverse trend was observed, where the 40-m tile spacing was found to have significantly greater carbon content than narrower tile spacings. Trends observed with carbon stocks per depth increment closely followed trends observed with carbon content at the same depth. However, no significant differences were observed among treatments with the summation of carbon stocks to the 1-m depth. Tile spacing did not have a significant effect on aggregate stability at any depth. The soil fertility data showed some indication of the potential translocation of soil calcium from the soil surface to lower depths in the soil profile resulting in significantly higher soil pH in the 5-m tile spacing than the 40-m tile spacing in all depths below 30cm. No consistent differences related to treatment were found with the cone penetrometer or vane shear penetrometer measurements. After 35 years of drainage history, tile drain spacing did not have a significant effect on total carbon stocks to the 1-m depth, but rather seems to have had a significant effect on the vertical distribution of soil carbon content throughout the soil profile.</p>

Doctor Scientiae / Acid Mine Drainage (AMD) is identified as one of the contributors to environmental hazard in the gold mining region of South Africa, as caused by the mining operational activities performed by mining industries in South Africa. This effect motivates the development of AMD prediction techniques application and geochemistry modelling using gold tailing dams located in West Rand area, Witwatersrand Basin as a case study. Control strategies are devised to assess, understand and measure the acidic potential generation of waste materials in ensuring the right method required to analyse risks caused by AMD to environment. The method encompasses mineralogical and geochemical analysis of 93 samples collected, AMD prediction, test modification and geochemical modelling. This method was appropriately applied to understand the basic mechanisms involved in controlling acid generation, assessing prediction procedure and selecting the right prediction tools. Study objectives are attained by performing a series of experimental lab tests on the samples collected from the two major tailing dams (Mogale and Gold One_1 tailings). Results derived from the lab experiments (XRD and SEM-EDS) show presence of mineral phases characterised with the surface feature of samples, and unknown substances of samples were identified. Geochemical characterisation was performed by XRF and ICP-MS to determine the major oxides elements and trace elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical analysis is used to interpret the data derived from geochemical characterisation process to explicate the metal and trace elements distribution and occurrence. Initial samples were screened and categorised based on paste pH and EC using kinetic tests to determine acid-forming and neutralising minerals in samples and static tests to determine acid generation potential in samples. Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter downward the holes to 10 meters, with a few meters samples in hole T003 at Gold One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA ratio was applied to assess the risk of acid generation from mine waste materials. Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate the net acidic generation potential trends of samples, which were classified into non-acid forming, potential acid forming and uncertain categories. Results integration between ANC, Single Addition Net Acid Generation (NAG) test and NAPP were used to classify acid generation potential of the samples. Leachate collected from leaching column test were analysed for pH, EC and chemical element by ICP-MS. The leaching column test used to analyse samples (T004) and (T001) collected from the two major tailings was set up for a 4-month experiment. Study findings present environmental assessment report on the two investigated gold tailing dams in Witwatersrand Basin area. Other findings are improved understanding of the application and limitations of various existing AMD prediction methods for assessment of gold mine waste and conceptual geochemical modelling developed to test appropriate methodology for AMD potential at a given gold mine site.

Colloid-borne Heavy Metals in the Drainage Gallery of an Abandoned Zn-Pb-Ag Mine (in German). The colloid inventories and the colloid-borne heavy metals in the Rothschönberger Stolln adit, the main drainage gallery of the Freiberg, Germany, mining district, were investigated. This adit runs from Freiberg to the village of Rothschönberg, where it flows into the river Triebisch, a tributary of the river Elbe. The water of the adit is a typical mine water from a flooded ore mine. The main reason for choosing the Rothschönberger Stolln adit for colloid investigations was that ample knowledge concerning the origin of the water and the geology of its catchment area exists. The aim was to characterize the colloids at the mouth of the adit and to elucidate if important contaminants occur in a colloid-borne form. A colloid concentration of about 1 mg/L was found. The particles have a size of 50 to 150 nm. They primarily consist of iron and aluminum oxyhydroxide and carry trace elements such as Pb, As, Cu, Y, La. The contaminants Pb and As are almost entirely colloid-borne. Colloids can have both a retarding and a stimulating influence on the transport of contaminants. The existence of colloids should be taken into account if mine waters flow to the biosphere or if mine waters are to be purified by permeable reactive barriers.