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Effect of Cromium(Cr(VI)) and Nickel(Ni(II)) on microbial growth and bioremadiation rates in soil

Tzavellas Vasileios

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Summary

Soil is one of the most important elements of the environment equally important for human health and for the smooth functioning of the environment as it is a means of storing both groundwater and cultivation medium. In recent years, due to the gigantic growth of the industry, it has been observed that land quality has been deteriorated considerably due to the inappropriate use of fertilizers, pesticides and the uncontrolled dumping of industrial waste. One of the common pollutants present in the soil are hexavalent chromium (Cr (VI)) and nickel (Ni (II)).Up to now, several technologies have been developed to clean up contaminated soils, some of which have high costs both in their operation and in their subsequent maintenance.The most economical of these methods seems to be the biodegradation of pollutants with the contribution of micro-organisms already in the ground.Thus, the objectives of this diploma thesis are to test the resistance of certain bacteria isolated from water and soil to different concentrations of Cr (VI) and Ni (II), but also their ability to bioremediate soil polluted by these metals. More specifically the bacteria used in this work were:Curtobacterium sp., Pseudomonas sp., Streptococcus sp., Chryeobacterium sp., Paenibacillus sp., some strains Enterococcus faecalis and Escherichia coli, Streptococcus sanguinis , Pedobacter sp and Staphylococcus sp.The experiments were performed in two stages. Initially, the resistance of all strains was tested at various concentrations of Cr (VI) and Ni (II) following the microarray method in broth as the CLSI protocol was used (Clinical and Laboratory Institute, January 2012).In this way, the minimum inhibitory concentration of each metal was determined for the bacterial strains in question (Minimum Inhibition Concentration-MIC). VI) equal to 50mg / L and Ni (II) equal to 4mg / L and their ability to reduce the concentration of specific metals in soil samples was tested.The results obtained at the end of the experiments show a marked decrease in the concentration of the two metals . Specifically for Cr (VI) and soil bacteria, the highest reduction in Cr (VI) concentration was reported by the Curtobacterium sp.strain with a removal rate of 98.61%.Also of the water bacteria for Cr (VI) the highest removal was shown by theE.coli "B"strain with removal rate of 98.48%. Finally, the results for Ni (II) showed that the most effective of the soil bacteria was Pedobacter sp. strain with a removal rate of 96.76% and from the water bacteria the most effective was E.coli "C"strain with a removal rate of 95.89%.

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