Immobilization of sulfate reducing bacteria

In view of the difficulty in treating the bioleaching solutions, the selective precipitation of metals using H2S produced biologically by sulfate reducing bacteria (SRB) was as an alternative process. At first, the initial COD/SO42- ratio and pH value were determined, and then the capability of different immobilized carriers was investigated by batch experiments. The results showed that high removal rate of SO42- was achieved when the initial COD/SO42- ratio was 3 and the initial pH value was 7. In the experiments, it was found that two factors were important for influencing the formation of biofilm and the reducing capability of SRB, the roughness of the immobilized carriers and the pore volume. There was no biofilm found when glass beads were immobilized carrier, and the reducing capability of SRB was low, the removal rate of SO42- was only 50%. Furthermore, the removal rate of SO42- increased with the pore volume of immobilized carriers. So, in view of the stability of process and the removal rate of SO42-, polyurethane foam was top priority as the immobilized carrier in the experiments, the removal rate of SO42- with it reached 95%, and the process was easily operated.