The effect of pH and temperature on biological sulphate reduction

Abstract

Acid mine drainage (AMD) is a worldwide problem caused mainly by mining activities and is known for its adverse impacts on the environment due to low pH, high metal content and high sulphate concentrations. Lime neutralisation is a conventional way of treating AMD, however, this method is costly and produces sludge that is difficult to dispose of. Biological treatment of AMD using sulphate reducing bacteria has been identified as a cost-effective alternative treatment method due to its advantages that include simultaneously precipitating metals, reducing sulphate concentration and increasing pH. In this study, the effect of temperature and pH using complex organic compounds as substrates in a downflow packed bed reactor was investigated. Temperature was found to have a major impact on sulphate reduction. Sulphate reduction dropped from about 88 % to about 67 % when the temperature was slowly decreased from 30 °C to 10 °C. The decrease in pH from pH 6 to pH 5 was observed to have minimal effect on sulphate reduction.