Biohydrometallurgy in Bulgaria – Achievements and Perspectives

The past and current research and industrial activities in the field of biohydrometallurgy in Bulgaria cover a large number of problems: microflora of different mineral deposits (such as of ores of non-ferrous metals, uranium and gold; non-metallic mineral raw materials such as coal, oil, kaolins, quartz sands, etc.); physiology, biochemistry and genetics of the microorganisms participating in the transformations of the above-mentioned mineral substrates; bioleaching of copper and other non-ferrous metals and uranium by means of in situ, dump, heap and reactor techniques; pretreatment of gold and silver-bearing sulphide concentrates and ores by means of chemolithotrophic bacteria to expose these precious metals; combined microbial and chemical leaching of precious metals from oxide ores; microbial removal of iron from quartz sands and kaolins, of sulphur from coal, of silicon from low-grade bauxites, of phosphorus from iron ores; improvement of the ceramic properties of kaolins; microbial enhanced oil recovery; electricity production from organic wastes by means of microbial fuel cells. Several of the above-mentioned activities are connected with the solution of essential environmental problems: prevention of the generation and/or treatment of toxic waters polluted by heavy metals, radionuclides, arsenic, oil, organochemicals, etc. by means of active and/or passive systems, reactive zones, rock filters, etc.; treatment of soils polluted with the above-mentioned pollutants by different reactors, heap and in situ techniques; bioremediation of post-mining landscapes and wastes.