Abstract:
This study was aimed to replace the chemical and physical treatment with biological treatment to save the environment. It was concerned with the isolation, screening, and charact erization of heavy metal-resistant bacteria isolated from Kombolcha tannery industry effluent. Different ways were used to select the maximum of isolates resistant to heavy metals. Based on, morphological, gram stain and biochemical tests six resistance bacteria were isolated by using free nutrients agar medium and nutrient broth.The isolates showed 2225 ppm Cr, 1100 ppm Hg and 340 ppm Pb of MIC.The isolates are, Klebsiella sp. (B-02), Pseudomonas sp. (B03),E. Coli (B-15), Enterobacter sp. (B-25), Salmonella sp.(B-51)and Clostridium sp. (B-54). From the six isolated bacteria, Klebsiella spp. and Salmonella sp. were resisted up to 2200 ppm Chromium. Whereas, Pseudomonas sp.and E.coli were resisted .Lead up to 340 ppm and Enterobacter spp.and Clostridium sp. were resisted Mercury i.e. up to1050 ppm. The study on the morphology of resistant isolates showed that the contour and the size of colonies would change in the presence of heavy metals. The concentrations of heavy metals (Crand Pb) in the isolated bacteria (B-03 and B-51) and tannery effluent were determined by using flame Atomic Absorption spectrometer .Concentration of Lead and Chromium in the bacteria were found to be in the range: 0.015-0.0156, and 0.0182-0.0185, respectively and 0.02-0.023 and 0.0030.00325 in the effluent sample. The TEWW had contained maximum Iron and minimum Chromium.Depending on the results, all resistant isolates allowed determining the order of toxicity of the different metals was as follows: Pb>Hg > Cr. The redaction capacity of Chromium, Mercuryand Lead resistance bacteria were 90%, 85% and 80% respectively. Increasing of metal concentrations on the isolate showed a significant toxic effect for the bacterial growth and metabolism. Chromium in the original effluent sample was by far less th an the permissible limit; these shows, the microbes in the tannery effluent have a capacity of bioremediation of heavy metals and other wastes
