A Study on Survival and Chromate Reducing Ability of Bacterial Isolates in Tannery Effluent

Rapid industrialization coupled with rapid growth of human population has brought about hazards of environmental pollution. The tanning industry is a major source of water pollution and a threat to the environment due to indiscriminate use of chromium. The reduction-mediated immobilization of Cr (VI) to Cr (III) is a useful process for remediation of Cr (VI) affected environments. The conventional physico-chemical methods for the treatment of Cr (VI) contaminated soil and groundwater are relatively lengthy and expensive as they are energy intensive and require large quantities of chemical reagents which can sometimes generate secondary wastes that require subsequent disposal and do not completely reduce chromium (VI). In view of these treatment shortcomings microbial reduction of toxic hexavalent chromium can be obtained by utilizing microbes in waste water which is cost-effective process and does not produce secondary wastes. The present study aimed to identify and evaluate chromate reducing strains of bacteria from tannery effluent. Seven bacterial strains were isolated from tannery effluent and were identified as members of genera Staphylococcus, Bacillus, Citrobacter and Pseudomonas. The hexavalent chromium reduction and its simultaneous conversion to chromium (III) by the strains were studied in minimal broth medium (with glucose) containing potassium dichromate at various concentrations ranging from 250 mg/l to 1000 mg/l. All the isolates could grow as well as reduce Cr (VI) even at concentration of 1000 mg/l. Qualitative analysis of Cr (III) was also performed.