[Isolation of Thiobacillus ferrooxidans and its application on heavy metal bioleaching from sewage sludge]

An iron-oxidizing strain, Thiobacillus ferrooxidans, was isolated from sewage sludge through incubation in the 9K-selected liquor medium followed by inoculation in Leathen solid plate. The strain can survive and propagate rapidly in sewage sludge with the addition of ferrous sulfate or sulfur powder as its energy substance. The pH of the sewage sludge inoculated with Thiobacillus ferrooxidans can be reduced to 1.80 from initial 7.86 within 6 days for bioleaching. Compared to the control without the addition of the strain, the treatment with Thiobacillus ferrooxidans exhibited a high ability to oxide Fe2+ and sulfur in the first 6 days during bioleaching. A batch experiment further demonstrated that as high as 100%, 100% and 80% of the removal efficiency of Cu, Zn and Cr in sewage sludge could be obtained, respectively, in the period of 4-10 days bioleaching by using the isolated strain.