Removal of Contaminants from Water by Bacterial Activity

Abstract

High concentration of sulphates and metals in waters is often as a consequence of anthropogenic activity and industry. The principles of the biological-chemical methods for pollution removal include various processes. The most widely metabolic pathway of sulphate-reducing bacteria - overall dissimilatory reduction - is the complete reduction of sulphate to hydrogen sulphide. Two major metabolic groups are known, depending on whether or not they can oxidize acetate. One group utilizes lactate, fumarate, propionate, butyrate, pyruvate, and aromatic compounds, which they typically oxidize to acetate, while the other group oxidizes acetate to CO₂ and H₂O. Sulphate is reduced to H₂S through a series of intermediate reactions. The end product of this reaction, hydrogen sulphide, can react with metal ions to form insoluble metal sulphides or reduce soluble toxic metals, often to less toxic or less soluble forms. This way, sulphate-reducing bacteria are utilizable in bio-elimination of sulphate and metal from water.