Bacterial Bioremediation of Heavy Metals in Tannery Effluent

The tannery effluent was collected from the Vellore district of Tamil Nadu, India and bioremediated. Physico - chemical characteristics of the collected tannery effluent was analyzed. The tannery effluent was acidic nature with brown colour and emitted unpleasant smell. High value of TSS and TDS and BOD and COD, calcium, magnesium, sodium, potassium, fluoride, nitrate, nitrite, sulphate and the toxic heavy metals chromium, nickel, zinc, copper and iron were recorded in the collected tannery effluent sample. Ten different bacterial isolates viz., Pseudomonas sp. (P1), Proteus sp., Bacillus sp., Escherichia sp., Serratia sp., Pseudomonas sp. (P2), Staphylococcus sp., Enterobacter sp., Alcaligenes sp., Micrococcus sp. and Staphylococcus sp. were identified. The bacterial isolates were screened for its resistance against toxic heavy metals. All the ten isolate were resistant to all the heavy metals. Heavy metal adsorption by living bacterial cells (Bioaccumulation), dead bacterial cells (Biosorption) and immobilized bacterial cells (Immobilization) was studied. Immobilized (Sodium alginate) bacterial cells were considered as the best was for the bioremediation of heavy metals. The bacterial isolates which were identified in genus level were subjected to 16S rRNA sequencing and identified in species level. The bacteria Bacillus sp. confirmed as was confirmed as Bacillus subtilis, Serratia sp. was confirmed as Serratia marcescens and Pseudomonas sp. was confirmed as Pseudomonas fluorescens. The bacterial isolate Bacillus subtilis, Serratia marcescens, Pseudomonas fluorescens were selected for optimization study based on heavy metal adsorption. The collected tannery effluent was inoculated with (immobilized beads) 5 per cent inoculum containing >105 cfu/ml of bacterial consortium (Bacillus subtilis + Serratia marcescens + Pseudomonas fluorescens), and air was passed continuously using an aerator. After 6 months, the sample was filtered under aseptic condition and physico - chemical parameters were estimated. The colour of the bioremediated tannery effluent sample was black to colourless and odorless. The physico - chemical characteristics of the bioremediated tannery effluent was significantly reduced after 6 months.