Bioprecipitation for heavy metals removal from Acid Mine Drainage

Main aim of this paper was to perform a feasibility analysis of a bioremediation process by sulphate-reducing bacteria (SRB) for toxic metals removal from acid mine drainage (AMD) samples, in a relatively cheap and environmentally friendly way. The treatment of AMD by the SRB is based on the ability of these bacteria to reduce sulphates to hydrogen sulphide, which binds readily with most metals to form an insoluble precipitate. It was investigated the kinetic of Cd precipitation by SRB of Desulfovibrio sp. The present experimental work was carried out in the framework of the S&T Cooperation Programme between Italy and Albania (years 2005-2007). The study represents a preliminary investigation on AMD coming from an Italian mine, with the main aim to transfer this technology - very interesting under the environmental point of view to treatment of Albanian AMD samples. Preliminary results have been encouraging and have demonstrated that strains of Desulfovibrio are able to bioleach Cd from AMD; in fact, about 90% elimination of Cd by bacterially produced H2S after 45 minutes. Experimental tests data have been used in order to perform a preliminary techno-economic feasibility analysis of the process, aimed at metal removal from AMD. A treatment cost of about 0.7 EUR/m3 AMD has been estimated, for a plant capacity of 1 m3/h AMD inlet flowrate.