Concomitant Treatment of Tannery and Paper Mill Effluents Using Extremely Metal-Tolerant Sulphate-Reducing Bacteria

Environmentally recalcitrant pollutants (chromium and sulphate) from mixed effluents of tannery and paper mills were treated simultaneously using highly metal-resistant dissimilatory sulphate-reducing bacteria. The remedial efficiency of the bacteria appeared zero when the bacterial pure culture was employed without the addition of any growth substrate from external source, while the bacterial sulphate reduction and consequent metal removal appeared maximum when sodium lactate was added as growth substrate in another set of experiments. In this set of experiments, almost 100% precipitation of the chromium (700 ppm) occurred in the first 7 days of anaerobic incubation. Sulphate was also removed totally (1225 ppm) in the first 7 days of incubation. pH of the media remained in the neutral to slightly basic range throughout the experimental trial. The achievement of maximum remedial efficiency also depicts the ultimate preference of lactate as carbon source by sulphate-reducing bacteria. The outcomes of the present investigation can be fruitful for designing efficient, environment-friendly and economical bioremedial strategies.