Development of environmental technologies to remove heavy metals from industrial and municipal wastes

In the framework of the project solving were achieved next main results: 1) Deepening of theoretical knowledge on the possible technological applications of physicalchemical (electrochemical) and biological removal of toxic metals from municipal and industrial wastewater through literature searches. 2) Determination of the characteristics of geo-materials through mineral-petrographic analysis and chemical and waste water samples by chemical analysis. Collecting data on selected samples from polluted areas in the territory of Peru and on the Italian territory. 3) Development of methods of treatment of heavy metals present in urban waste water and industrial residue. Reducing direct and indirect metal with Sulphur-Reducing Bacteria (SRB) in a laboratory scale, identifying the appropriate process to different types of contamination. 4) Development of biohyrometallurgical treatments of sulphides containing antimony and arsenic by iron and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans, Thiobacillus ferrooxidans, Thiobacillus Thiooxidans) and sulfate-reducing (Desulfovibrio desulfuricans, Desulfotomaculum). 5) Development of an electrochemical circuit, with the identification of critical process parameters. 6) Determination of the electrochemical process on a laboratory scale with the study of relevant parameters. 7) Optimization of physical and chemical processes (electrowinning) and biological on laboratory scale. 8) Scale-up of the processes. The main purpose of the studies was to clean up the toxic metals from municipal wastewater and industrial waters such as acid mine drainage (AMD), by applying the processes of electrowinning and bioprecipitation. The samples were collected from zinc mines located in Italy and lead and zinc deposit in Perù. The electrochemical process has allowed a high removal of heavy metals, allowing, with low energy consumption, significant recoveries (90-99% Zn). Culture of sulphate-reducing bacteria (SRB) of genera Desulfovibrio sp. and Desulfotomaculum sp. were used for the bioprecipitation tests. The kinetic of the selective precipitation of Cu and Zn of AMD by SRB has been investigated. This method has been performed in two interconnected reactors. Achieved results demonstrate the about 95-99% elimination of Cu and Zn by bacterially produced H2S. Both the electrowinning and bioprecipitation processes have been demonstrated the technical feasibility to decrease the heavy metals concentration.