The treatment of acid mine drainage (AMD) by sulfate-reducing bacteria (SRB) has been reported in the literature as a possible alternative to chemical treatment. The overall objective of this study was to implement such a treatment process at the mine site and specifically within the open mine pit itself. The first step of this study was to characterize process parameters. To accomplish this, a reactor was designed and built to simulate hydrodynamic conditions found in the mine pit. This reactor contained a 6$ sp{ prime prime}$ deep gravel bed in which a mixed population of SRB was inoculated. The operation of this reactor demonstrated that treatment of a continuous flow of AMD by SRB was possible, however, the response to changes in the composition of the AMD and to flow conditions was limited. The results indicated that further studies should be directed at the gravel bed itself since this was where the SRB are located and is the active site within the system. / The role of various physical parameters of a gravel bed in the biological treatment of AMD by SRB was examined. This was accomplished by using gravel of different sizes (0.25$ sp{ prime prime}$ vs. 0.5$ sp{ prime prime})$ and composition (granite vs limestone) to form 12$ sp{ prime prime}$ beds in a series of column reactors. The difference in size results in variations in the total surface area, the void volume and various volume ratios within the system. The effect of potential geological buffering by limestone was examined by using and comparing with beds composed of granite. / The gravel beds were inoculated with a mixed culture of SRB and overlaid with 6 L of AMD. After the SRB were established, a series of experiments were performed in which 16.7%, 25%, 75% and 100% of the water column was replaced with an equivalent quantity of fresh AMD. Changes in pH, ORP, electric conductivity, and concentrations of metal and sulfate were monitored for at least 28 days. Sulfate and metal removal at days 7 and 28 of each experiment were compared. The SRB can tolerate a wide range of disturbances, however, an increase in the load of fresh AMD decreased the performance of the system. The results indicated that the total surface area is of greater importance than the void volume in the overall treatment process by SRB. / A dimensionless number was constructed to describe the relationships between the physical parameters of the gravel bed. A plot of the proportion of sulfate removed and this dimensionless number could provide essential information for the sizing of a gravel bed for the purposes of sulfate reduction. This was done for each type of gravel and comparison of the two curves indicated that there was no significant difference between the two gravels. / The importance of the physical substrate for the SRB has been reported in the literature. However, no known attempt has been made to quantify the relationships between the physical parameters and the biological activity. Such information would be useful for the sizing of wetlands and other passive treatment system that uses SRB activity for the purposes of treating AMD. This study is a step towards filling this void.

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Thesis (M.Sc.)--University of the Witwatersrand, Faculty of Science, School of Geosciences, 2017. / The costs of acid mine drainage (AMD) monitoring result in the quest for alternative noninvasive method that can provide qualitative data on the progression of the pollution plume and ground geophysics was the ideal solution. However, the monitoring of AMD plume progression by ground geophysics (time-lapse electrical resistance) proves to be noninvasive but also time consuming. This study focuses on the modeling of different geophysical anomalies (mainly geoelectrical resistivity response) of the karstic aquifers. The models are generated from field parameters such as the electrical resistivity of the host rock and the target rock, depth to the target, noise level and electrode configuration in order to ensure that the model outcomes represent the actual field data. This process uses Complex Resistivity Model (CRMod) and Complex Resistivity Tomography (CRTomo) to generate geoelectric subsurface models. Different resistivity values are applied to targets in order to assess the difference against the baseline model for each target scenario. The resistivity difference is reduced to smallest possible value between the reference and new models in order to gauge the lowest percentage change in the model at which the background noises start to have impact on the results. The study shows that the behavior of targets (aquifer) could be clearly detected through resistivity difference tomography rather than inversion tomography. The electrode array plays a significant part in the detection of target areas and their differences in resistance because of its sensitivity. This therefore indicates that the electrode array should be chosen according to study requirements. Furthermore, this study shows that the modelling of different target sizes, alignments and shapes plays huge role in the final results. Future studies that can provide a correlation between the field quantitative data from sampling and the model outcomes have the ability to add to the knowledge of geophysical modeling, thus reducing costs associated with field based plume AMD monitoring. Key words: Acid mine drainage, geophysics, karst aquifer, complex resistance, modelling, tomography / XL2018

A dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfilment of the requirements for the award of Master of Science degree, 2017. / Mining is an integral sector of most developing countries and it is a highly lucrative industry that has been in existence for centuries, and assumes an essential part in their economies. However, the legacy of mining in these countries has posed a threat to underground and surface water as a result of contamination arising from Acid Mine Drainage (AMD). Bearing in mind the environmental and ecological impairment posed by AMD there is a need for innovation in the treatment of AMD, to enable financially savvy treatment of the contaminated waters. This research is focused on the extraction of U(VI), As(III) and As(V) from synthetic metal solutions as well as field removal of these metal ions by application of iron hydroxide/oxide-modified zeolite. Batch experiments were performed to evaluate the effectiveness of iron hydroxide/oxide-modified zeolite as a potential low-cost sorbent for extracting As(III), U(VI) and As(V) from AMD. The research approach was based on the possible changes that can occur to a zeolite surface that has been in contact with an iron-laden solution. Zeolite is a commonly used adsorbent, but fewer studies have explored changes that it undergoes as an adsorbent on contact with iron solutions. Thus, the study involved modifying zeolite with iron hydroxide/oxide, which are the main precipitates of iron in the environment and which can possibly alter the adsorption properties of zeolite. Batch extraction studies were performed using the modified zeolite. In paper I, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The kinetic data for As(V) adsorption by iron (hydr) oxide-modified zeolite model fit well into pseudo second-order and the adsorption capacity was obtained as 0.080 mg g-1. The application of iron (hydr) oxide modified zeolite on AMD for As(V) recovery showed that > 99% of As(V) was extracted from the solution. The high removal efficiency of oxyanionic arsenic species was attributed to arsenic forming complexes with iron oxyhydroxide surface on the surface of the sorbent. Paper II dealt with adsorption of U(VI) from aqueous solution by application of iron hydro (oxide)-modified zeolite in a single-component system. Parameters such as: solution pH, contact time, adsorbent dosage, initial concentration and temperature were optimized before field application to real acid mine drainage. The optimum parameters for U(VI) adsorption were: adsorbent dosage (3.0 g), solution pH (6 ±0.1) and contact time (30 min). Optimum parameters where then applied to acid mine drainage were the effluent was found to be cleaner than the influent. In Paper III, iron oxide-coated zeolite (IOCZ) nanocomposite was prepared and fully characterized. This sorbent was then used for extraction of U(VI) and As(III) from aqueous solutions by application of batch techniques. Batch study results were modelled best by the pseudo second-order kinetic model and Freundlich isotherm. The adsorption capacity of both U(VI) and As(II) was dependent on the temperature. The presence of Cd2+, Co2+ and Cr3+ ions enhance the adsorption of As(III) whereas the opposite trend was observed for U(VI) sorption onto IOCZ nanocomposite. / XL2018

The use of algae as heavy metal bioindicators in aquatic environments has received much attention. In this study, the performance of a common freshwater living green alga, Cladophora sp. as a mercury bioindicator and its potential for phytoremediation applications was assessed by various parameters which included the influence of contact time, pH, initial mercury concentration and the presence of competing metal cations. A rapid uptake of mercury by Cladophora sp. was displayed. More than 99% of mercury in solution was removed within the first 5 min of contact and equilibrium was attained after 10 min. High adsorption capacities of 800 mg kg-1, 530 mg kg-1 and 590 mg kg-1 at pH 3, 6.5 and 8.5 respectively were obtained at the optimum mercury concentration of 1.0 mg l-1. Competitive adsorption studies showed that the selectivity of heavy metal cations by Cladophora sp. was in the following order: Hg2+ ˃Fe2+˃Cu2+˃ Zn2+ ˃ Co2+. These results indicate that living Cladophora sp. algae are suitable for use as mercury bioindicators in AMD waters and are also suitable for the removal of mercury in AMD conditions.

The Williams Brothers Mine is located in Mariposa County, California. Surface waters from the site drain into the south fork of the Merced River and the San Joaquin River Basin. The mine was developed in the 1980s and mined intermittently until 1996. In 1998, concerns of acidic drainage at the site arose. Effluent sampling by Engineering Remediation Resources Group (ERRG) found acid mine drainage (AMD) characterized by a pH of 3.9, sulphate concentrations of 100 mg/L and low metal concentrations of 0.074, 4.60, 1.23, 0.047 and 0.133 mg/L for Cu, Fe, Mn, Ni and Zn, respectively. The aim of this research was to evaluate passive treatment system alternatives for the mitigation of the AMD to meet water quality objectives for the San Joaquin River Basin. A bench-scale study was undertaken which consisted of 3 systems treating synthetic AMD: (1) a peat biofilter to remove dissolved metals followed by an anoxic limestone drain (ALD) to increase alkalinity and pH; (2) a sulfate reducing bacteria (SRB) bioreactor followed by an ALD, in which SRB reduce sulphate to sulfides, generating alkalinity and decreasing metal concentrations via metal sulfide precipitation; and (3) a SRB bioreactor. Synthetic AMD was produced to represent AMD characteristics observed at the site. The peat-ALD system effluent pH was 6.9 and concentrations of Fe and Cu decreased to below water quality objectives with concentrations of 0.008 and 0.06, respectively. The SRB-ALD and SRB system effluents met water quality objectives for pH and Cu, Ni and Zn metal concentrations. The effluent pH for both systems was 6.5. The SRB-ALD system reduced Cu, Ni and Zn to concentrations of 0.004, 0.016 and 0.025 mg/L, respectively. The SRB system reduced metal concentrations for Cu, Ni and Zn 0.006, 0.010 and 0.027 mg/L, respectively. Based on the bench-scale study, the pilot-scale system consisted of a combined passive treatment system containing a peat biofilter, SRB bioreactor and a limestone drain. Pilot-scale testing commenced on May 23rd, 2007. To date, some metal attenuation has been observed, with average effluent concentrations of Cu, Fe, Mn, Ni and Zn equal to <0.005, 0.92, 0.45, <0.005 and 0.049 mg/L, respectively. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2008-01-29 12:42:03.58

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Thesis (Ph.D.)(Microbiology and Plant Pathology (Water resource management))--University of Pretoria, 2007. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.