Office for Environmental Programs - Theses
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ItemEvaluation of the suitability to use sulphide-reduction bacteria in wetlands and bioreactors to bioremediate acid drainage from copper mining in Ecuador( 2012)Large scale-mining of copper industry is going to be developed in Ecuador as one of the major goals to diversify the country's economy. The first large scale-mining project is in the field "Mirador" located in Zamora Chinchipe province, Ecuador. This field is an open pit copper mine from where it will be extracted 60000 tonnes of copper ore per day. Two rock dumps located in each of the sides of the pit will contain 44% of the extracted ore in the form of sulphide ore (mostly chalcopyrite), which if it is exposed to water and oxygen will form Acid Mine Drainage (AMD). AMD is characterised to have low pH, high concentration of sulphates and heavy metals. Due to high rainfall rates and geo-chemical characteristics of waste rocks in the Mirador Project, AMD produced will be in high flows and highly concentrated. It will threaten water quality and fisheries of the watersheds surrounding the mine site, thus causing environmental, social and economical impacts. As AMD is a complex problem in biological, chemical and ecological terms, its remediation is also complex. Aspects like climate and terrain of the Mirador Project, scale of its mining operation, and pollution prevention measures for AMD are addressed in this research to evaluate how they can influence the application of AMD remediation techniques. This research focuses on the bioremediation of AMD by using Sulphate-Reducing Bacteria (SRB) in anaerobic wetlands and bioreactors as a possible sustainable alternative. SRB are capable to treat AMD by increasing pH, sulphate reduction and metal remotion. To evaluate if SRB are suitable to be used in bioreactors and wetlands to treat AMD in the Mirador Project, this research analyses the most important factors that influence the growth and long-activity of SRB: substrate, pH, temperature, toxicity of metals and heterogeneous microenvironments. In addition, an analysis of the wastes produced by bioremediation of AMD with SRB and their management mechanisms is conducted to show that this bioremediation system may be sustainable in terms of energy efficiency, economic viability and little generation of waste. Finally, the evaluation of suitability of SRB in anaerobic wetlands and bioreactors is developed by considering AMD characteristics, topography and climate conditions of the site. Since the Mirador Project is still in his exploration phase, planning of AMD sustainable management is still on time to be addressed. This research recommends developing a phase scale study to decide what the best treatment option for AMD produced in the waste rock dumps in the Mirador Project could be. The outcomes of the evaluation conducted in this research show that application of SRB may be suitable to remediate AMD in an anaerobic bioreactor. This literature review could be used to establish a framework of action to manage AMD mitigation and remediation since its results could be useful for other mining operations with similar conditions in Ecuador
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ItemInvestigating the potential for thiocyanate bioremediation in a gold mine in Stawell, Victoria( 2010)Bioremediation is a cost-effective way of removing environmental contaminants like thiocyanate, which is associated with various industrial processes. Certain species of bacteria have been found to be capable of oxidising thiocyanate into sulfate, thus removing thiocyanate in the system. This project aims to investigate current and future applications of bioremedation on thiocyanate contamination in a gold mine in Stawell, Victoria through analysis of historical data, gathering information on in situ geochemical conditions, gaining an understanding of thiocyanate oxidation via reduction of nitrate and iron, and enrichment and isolation of thiocyanate-degrading bacteria or microbial communities. Particular focus was placed on thiocyanate concentrations in the Stawell Gold Mine Tailings Dam No. 2. Results from the desktop study indicate that thiocyanate is a redox reactive chemical species and is probably transformed into sulfur. The minerals in the mine tailings are not the likely source of thiocyanate concentrations. Instead, thiocyanate is likely to be from a cyanide and sulfur that is leached from an unknown source. The investigation of thiocyanate oxidation via ferric oxide synthesis indicates that in situ thiocyanate oxidation is more likely to proceed through enzymatic reactions or microbial catalysts and likely to be coupled with nitrate reduction. Inconclusive results from the enrichment and isolation of thiocyanate degrading microorganisms suggest that thiocyanate degradation may potentially occur in experimental conditions different from what was investigated in this study.