Heavy metal biosorption by three bacteria isolated from a tropical river

Abstract

Bioaccumulation (bioconcentration) of four heavy metals cadmium, lead, zinc and nickel by three bacteria Bacillus, Staphylococcus and Pseudomonas as a tool for the decontamination of heavy metal impacted aquatic systems was investigated . The bacteria were obtained from the New Calabar River. Monitoring of the physicochemical parameters of the river water and sediment revealed upstream downstream increases in their levels. Ranges for riverwater parameters were temperature (23 to 270C), pH (5.34 to 5.84), alkalinity (12.0 to 18.8mg CaC03/L), dissolved oxygen (6.24to 6.92mg/L), total suspended solids (1.13 to 1.61mg/L), conductivity (2.15 to 2.39 mS/m), chloride (3.0 to 10.20mg/L), biochemical oxygen demand (2.0 to 2.5mg/L) and chemical oxygen demand (4.0 to 10.0mg/L). Ranges for sediment parameters were temperature (20 to 250C), pH (5.3 to 6.97), conductivity (2.55 to 4.22 mS/m), dissolved oxygen (3.2 to 4.22mg/L), chloride (3.5 to 15.3mg/L), biochemical oxygen demand (5.5 to 10.5mg/L) and chemical oxygen demand (20.7 to 100.6 mg/L). River water heavy metals levels were lower than sediment levels. The river water ranges were; Cu (0.01 to 0.05mg/L), Pb (0.01 to 0.02mg/L), and Zn (0.01 to 0.07 mg/L). Sediment heavy metal ranges were Cu (1.09 to 1.45 mg/L), Pb (0.03 to 0.07mg/L) Cd (nd to 0.009mg/L) and Zn (0.27 to 1.27mg/L). The percentage accumulation of heavy metals by Bacillus, Staphylococcus and Pseudomonas after 24h of exposure to heavy metals were Cadmium; 68.6% , 58.4% and 28.3%, Nickel; 94.5% , 85.7% and 90.8%, Lead; 91.6%, 68.1% and 52.9%, Zn; 71.6% 72.1% and 77.0% respectively. The ease of bioaccumulation of the metals by bacteria showed the following trend N1 > Zn > Pb > Cd. Cadmium was the most toxic of the metals to the bacteria. Lead and Zinc displayed similar levels of toxicity, while Nickel was the least toxic. Bioaccumulation potentials of the three bacteria indicated that Bacillus showed the highest potential this was followed by Staphylococcus while Pseudomonas showed the least potential. These results indicate that bacteria especially Bacillus may be employed in the bioremoval of heavy metals from tropical aquatic environments impacted with heavy metals.



Key Words: Bioaccumulation, Bioconcentration Heavy metals, Decontamination, Bacteria.

[Global Jnl Environ Sci Vol.2(2) 2003: 98-101]