Abstract :
Acid mine drainage (AMD) is one of the most serious forms of water pollution in industrial and post-industrial areas of the world. Whilst the significance of acidophilic bacteria in the genesis of acidic effluents is well understood, their potential for controlling AMD pollution has received relatively little attention. Microorganisms indigenous to highly acidic, metalliferous environments are highly diverse, and include bacteria that catalyse the reduction, as well as the oxidation, of iron and sulphur. Since these reduction reactions can generate alkalinity, they have potential in biological remediation in AMD. Reductions of ferric iron and of sulphate-sulphur are thought to be important in constructed wetlands, which are widely used for AMD mitigation, though the importance of acidophilic microorganisms in these ecosystems is currently unknown. Proposed schemes for processing AMD are described which utilise immobilized populations of iron- and sulphate-reducing acidophilic bacteria in a series of bioreactors. Conventional chemical mitigation (via addition of alkali and separation of the bulky ferric iron sludge which is produced) may also use immobilized acidophiles (iron-oxidizers) to facilitate the necessary step of ferrous iron oxidation. The possibility of using biological agents (such as acidophilic protozoa) to control the metal-mobilizing bacteria which are responsible for the formation of AMD, is discussed.
