POSSIBILITIES FOR USING BIOLOGICALLY-PRODUCED SULFUR FOR CULTIVATION OF THIOBACILLI WITH RESPECT TO BIOLEACHING PROCESSES

The growth of a mixed culture of thiobacilli was evaluated in batch cultivations using two different types of elemental sulphur; commercially available sulphur flower and a dried, biologically produced, sulphur. The latter material was produced by partial oxidation of sulphide under oxygen limitation by a mixed culture of neutrophilic thiobacilli. This step can be applied in practice to remove sulphides formed during treatment of sulphate-containing wastewater. The biologically-produced sulphur can be removed from the process water by sedimentation. Its reuse may become important once the application of the biological sulphur cycle is considered for the removal of heavy metals from a contaminated environment. Biologically-produced sulphur oxidized significantly faster than sulphur flower, resulting in higher rates of sulphuric acid production. With biological sulphur pH 1.5 was reached after 65 h, whereas with sulphur flower this pH was obtained after 160 h of cultivation. The biological-sulphur oxidation was accompanied by a disintegration of sulphur particles, resulting in a high homogeneity of the substrate in a growth medium. The presented findings indicated that the potential of bioleaching techniques may benefit from the reuse of biologically-produced sulphur.