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Abstract |
Mining is implicated as a significant contributor to water pollution, the prime reason being, that pyrites oxidize to sulphuric acid when exposed to air and water. Mine effluents, often containing sulphate, acidity and metals, should be treated to render it suitable for re-use in the mining industry, for irrigation of crops or for discharge in water bodies. This study describes the removal of all three mentioned pollutants in mine effluents, from different origins, containing different concentrations of various metals. The objectives were achieved, applying the biological sulphate removal technology, using ethanol as the carbon and energy source. It was shown that diluting the mine effluent with the effluent from the biological treatment, the pH increased due to the alkalinity in the treated water while the metals precipitated with the produced sulphide. When this treatment regime was changed and the mine water was fed undiluted, it was found that the metals stimulated the methanogenic bacteria (MB) as trace elements. This resulted in a high COD utilization of the MB, such that too little COD was available for the SRB. Metal removal in all three studies was observed and in most instances the metals were eliminated to the required disposal concentration. |
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