Water purification sludge as a substrate in metal bioleaching

The presented work analyses the efficiency, suitability and application prospects of bioleaching (by Acidithiobacillus thiooxidans) of metals from low contaminated waste - post coagulation iron sludge from groundwater purification. The test results showed a high bioleaching efficiency of over 90% for iron, but also for aluminium, manganese, calcium, magnesium and chromium. Lead, nickel and cadmium were in the sludge, although at low concentrations, were solubilised to 70%-80%. Process time was an important factor for the bioleaching effect. It was necessary to run the bioleaching process as a batch culture for at least 6 d. The efficiency of bioleaching was found to be independent of temperature. Both cultivation at 10degree celsius and 20degree celsius were suitable for the experiment and the achieved metal solubilisation efficiency was very comparable. Acidification of the sample was a key factor in the efficiency of the bioprocess. The inoculation of the studied sludge and the addition of elemental sulfur as an energy substrate were not significant factors for the solubilization of metals. The acidified sludge from groundwater purification was classified as a semi-finished iron (waste) coagulant and a good substrate for the growth of bioleaching microorganisms.