Abilities of Three Microorganisms for Cleaning Cadmium Contaminated Soils

Abstract

The abilities of three indigenous bacteria for bioremediation of cadmium contaminated soils collected from Agbabu Farm Settlement close to mining sites in Ondo state, Nigeria was studied to provide helpful information for soils remediation and soils health management in this sub-region for Millennium Development Goals accomplishment. Bacillus subtilis, Proteus mirabilis, and Escherichia coli isolated from the soils were inoculated into different soil samples conditioned with optimized factors determined from the first phase experiments. The conditioned samples were experimented for residual cadmium concentration with time in days using Atomic Absorption Spectrophotometer. The soil cadmium attenuation from the initial concentration of 70.21 mg/kg to below the maximum allowable of 3 mg/kg was hard for the organisms. Bacillus subtilis performed correction at time 35 days with an efficiency of 96.10 % and residual concentration of 2.74 mg/kg. Proteus mirabilis and Escherichia coli with respective, high efficiencies of 85.05% and 79.35% failed. The removal rate capacities were -0.131d-1 for B. subtilis; -0.111d-1 for P. mirabilis; -0.105d-1 for E. coli. Four kinetic models fitted described the experimental data well. The models assessment revealed the removals to be transport controlled as diffusion process was the rate-controlling step.

Keywords

• bioremediation
• biosorption
• cadmium removal
• contaminated soil
• diffusion
• heavy metals