Capabilities of Four Microorganisms for Bioremediation of Lead Contaminated Soil

This work studied the potentials of indigenous Micrococcus sp., Bacillus sp., Pseudomonas sp., and Escherichia coli (E. coli) for bioremediation of lead contaminated soils collected from Amita forest in Ebonyi State of Nigeria.The organisms isolated from the soils were conditioned with the predetermined optimum factors in inoculated soil samples. The samples were tested for residual lead concentration at times 8, 16, 24, 32, 40, 48, and 56 days with Atomic Absorption Spectrophotometer.The performances of the organisms were in the decreasing order of Micrococcus sp., Bacillus sp., Pseudomonas sp., and E. coli. Micrococcus sp. and Bacillus sp. performed earlier at time 16 days as against Pseudomonas sp., and E. coli at 24 days. The maximum efficiencies were discovered at time 56 days as 76.68%, 72.24%, 70.11% and 55.47% for Micrococcus sp., Bacillus sp., Pseudomonas sp., and E. coli respectively with respective residual concentrations of 31.55 mg/kg, 37.55 mg/kg, 40.44 mg/kg and 60.24 mg/kg at the respective efficiencies.The rates of removals were in the decreasing order of -0.0524d-1 for Pseudomonas sp., -0.0714 d-1 for Bacillus sp., -0.0743d-1 Micrococcus sp., and 0.113 d-1 E. coli. The fitted models showed diffusion as the rate-limiting step for removals by Pseudomonas sp., Bacillus sp., and Micrococcus sp.; while chemisorption was the rate-limiting step for removal by E. coli. This information will be helpful to researchers and decision makers for the remediation of lead contaminated soils.