Bioremediation of acid mine water using facultatively methylotrophic metal-tolerant sulfate-reducing bacteria

Abstract

A microbial process is proposed for the decontamination of acid uranium mine water high in sulfates and metals. Sulfate reducers are suitable for such a process. Anaerobic reduction of sulfate results in the formation of H 2S which leads to an increase in pH and the precipitation of the metals. As cheap an readily available carbon and energy source methanol was chosen. Six strains of sulfate-reducing bacteria were isolated from a waste water pond, one from a copper mine. All strains were found to utilize methanol as electron donor and carbon source. Other electron donors included lactate, pyruvate and acetate. The strains were not uniform in their morphology, cells were of different sizes and rod-shaped or curved. All strains stained gram-negative. Desulfovibrio salexigens DSM 2538, D. africanus DSM 2603 and D. carbinolicus DSM 3852 were used as reference strains. One of the isolates named UFZ B 378 was found to grow at pH 4.0, D. salexigens at pH 4.5, all other strains did not grow below pH 6.0. Culture media with varying sulfate and metal concentrations at different pH values were used to simulate the composition of the mine waters.