BIOREMEDIATION OF ACID MINE WATER USING FLY ASH AND DESULFOTOMACULUM NIGRIFICANS

摘要

One of the major concerns for the mining industry especially after the mine closure is the generationof acid mine drainage (AMD), and its discharge into the environment surrounding the abandonedmines, leading to serious environmental pollution. AMD is usually characterized by high concentrationof dissolved metal ions, sulfate and low pH. The efficacy of fly ash was assessed for the removal ofmetal ions such as iron, zinc and copper as well as sulfate from synthetic acid mine water. Completeremoval of ferric and ferrous, 80 per cent of Zn, 83 per cent of Cu and 62 per cent sulfate removalcould be achieved, with a concomitant increase in the pH value from 2.3 to 7 using fly ash as anadsorbent under appropriate conditions. The free energy of adsorption of the metal ions onto flyash was found to be negative, while the adsorption process was endothermic and adhered to theLagergren pseudo-first order rate equation. Bioremediation studies using a typical sulfate reducingbacterium namely Desulfotomaculum nigrificans, after pre-treatment of the synthetic acid minewater with fly ash, cumulatively resulted in about 94 per cent zinc, 100 per cent copper and 90 percent sulfate removal. The possible mechanisms of metal ion removal and sulfate reduction from acidmine water utilising Desulfotomaculum nigrificans are discussed.