Determination of Maximum Reduction of the Hexavalent Chromium Using Indigenous Bacterial Isolates

Tanneries generate wastewater in the range of 30 to 35L kg skin/hide processed with high salinity, high oxygen demand, high organic loading and a high salt content one of which is chromium which spoils the agricultural land and pollute the ground water. In the present investigation, the bacterial strains were isolated from the contaminated soil which was collected from in and around the tannery waste contaminated site. Previously grown indigenous bacterial culture was transferred into 100 ml nutrient broth containing different concentrations of hexavalent chromium (100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm and 700ppm). These were incubated for 72 hours in facultative conditions. The blanks were also maintained in same conditions without bacterial inoculation. Samples were collected from this experiment to evaluate hexavalent chromium at different time intervals (0hr, 12hrs, 24hrs, 36hrs, 48hrs, 60hrs and 72hrs). From the results it was inferred that the higher bacterial growth was observed at 48 hrs and the maximum chromium reduction was observed upto 500ppm, it was reduced at percentage of 90.40. The isolated microorganisms were identified as Pseudomonas fluorescens and Bacillus subtilis.