Isolation of Acidithiobacillus ferrooxidans from sulphur treatment plant, mine water and tailings of Anglogold Ashanti concessional area and their biooxidation potential of refractory ores

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The objective of the study was to find a candidate biomining organism Acidithiobacillus ferrooxidans in bioreactor tanks, mine water and tailings within the AngloGold Ashanti mining concession area with the aim of contributing to the development of biomining in Ghana as a sustainable mining practice. Samples from the Sulphur Treatment Plant (STP) bioreactor tanks, mine water, and soil tailings from the four geographical areas (North, South, East and West) of the Sansu dam were collected and assayed using 9K enrichment medium. Isolates were used for biooxidation over a 672 hour period and their oxidation potential assessed. A bacterium, which was acidophilic, chemolithotrophic with ferrous oxidizing potential, was isolated in ten out of twelve sample points. Isolates were also recovered from samples that were high in heavy metal (As, Fe, Cu, Pb, and Zn) concentration. The bacterial loads were higher in the bioreactor tanks (1.86 ×104- 4.24×105) compared to mine water and tailings (6.33×103 -1.40×104) although these differences were statistically not significant (P=0.05). The isolates grew best at pH 2 and a temperature of 35oC. Isolates could utilize sulphur and ferrous as energy sources. Biooxidation potential of the refractory ore was highest in isolates from the bioreactor tanks followed by mine water isolates and the tailings. Isolates from the bioreactor tank 146 showed the best biooxidation results. The presence of a candidate A. ferrooxidans isolate from the AngloGold Ashanti concessional area is an indication of the possibility of finding active indigenous strains of the bacterium which could serve as the basis for encouraging the massive use of the technology in Ghana’s mining companies.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Environmental Science.