Remediation of heavy metal-contaminated sediments by solid-bed bioleaching |
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Authors: | C Löser H Seidel P Hoffmann A Zehnsdorf |
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Institution: | (1) UFZ Centre for Environmental Research Leipzig-Halle, Dept. of Remediation Research, Permoserstrasse 15, 04318 Leipzig, Germany, DE |
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Abstract: | Weisse Elster River sediment from the Leipzig Lowlands region (Saxony, Germany) is anthropogenically polluted by heavy metals.
Sediment dredged from a trap to the south of Leipzig was characterized in detail. When freshly dredged sediment contacts air,
the material turns acidic because of oxidation processes, the heavy metals become soluble and the sediment poses an environmental
risk. We are therefore developing a sediment-treatment process based on heavy metal removal by bioleaching. Leaching experiments
were carried out in suspension and in the solid bed. The heavy metals were solubilized to nearly the same extent by H2SO4 dosage (pure chemical extraction) and addition of elemental sulphur (microbial oxidation of S0 to H2SO4). With increasing dosage of the leaching agent, Zn, Cd, Ni, Cu and Cr were more and more solubilized, whereas Pb was only
dissolved in small amounts. The addition of 2% S0 is considered an optimum dosage. When 5% S0 was added to the sediment, the pH dropped to 1.76 and large amounts of undesirable compounds such as Ca, Al and Fe were solubilized.
The higher the temperature, the faster the metals were solubilized in both suspension and the solid bed. The temperature optimum
for activating the indigenous S0-oxidizing microbes of the sediment lies between 30 and 40 °C. Conditioning of freshly dredged sediment with plants makes
it suitable for solid-bed leaching; the kinetics of heavy metal solubilization from sediment conditioned for 6 months with
Phragmites australis was the same as from long-term stored sediment.
Received: 26 November 1999 · Accepted: 5 May 2000 |
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Keywords: | Aquatic sediment Bioleaching Heavy metals Percolation principle Solid bed |
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