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Biotechnology for mercury remediation

Mercury salts and organomercurials are among the most toxic compounds in our environment. They are components of industrial waste and pollute soils and sediments. Physical or chemical decontamination processes available so far are expensive and result in highly toxic waste. Biological transformation of mercury compounds to metallic mercury by bacteria is a process which has been studied extensively at GBF. It appears as a cost effective, environmentally friendly and efficient alternative to existing technologies, especially at low pollutant loads. This has been demonstrated in a plant of pilot scale (0.7 m3 volume, up to 3 m3/h throughput) for mercury containing waste streams of the chlorine-alkali-electrolysis industry. The pilot plant consists of a mobile container housing a fixed bed reactor which is equipped with the necessary measurement and control devices and is fully automatized. The plant has been designed and constructed jointly by Preussag Wassertechnik GmbH and GBF. The pilot plant is inoculated with mercury resistant bacteria which have been isolated, identified and characterized by GBF. Mercury concentrations between 1 and 10 mg/l Hg are treatable by the microbial biofilm in the bioreactor with a removal efficiency of up to 99 %. The plant can be operated continuously for at least one year before regeneration becomes necessary. Regeneration takes place by elution of the mercury using oxidizing agents and recycling of the concentrate. From laboratory experiment it is estimated that a bioreactor of 1 m3 volume can clean at least 20.000 m of wastewater. The plant has been specially designed for chloralkali wastewater, but is adaptable to mercury containing aqueous effluents from other industries. Natural bacteria are currently used, however genetically improved bacteria have been constructed and may be used in the future.

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Gesellschaft fuer Biotechnologische Forschung mbH (GBF)
Mascheroder Weg 1
38124 Braunschweig
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