Biosorption and bioaccumulation of Cd and Ni in competitive solution by three bacteria isolated from polluted soils to sewage sludge

Background & Microbial biomass show high capacity for the remediation of heavy metals in contaminated solutions. This study aimed to isolate and identify the Cd and Ni resistant bacteria from the soils polluted to heavy metals and to evaluate the biosorption & bioaccumulation of these metals in competitive solution.
Materials & In this descriptive study, samples were taken from the soils polluted to waste water of farms nearby the water refinery in west of Ahvaz. The Ca and Ni resistant bacteria were isolated and their identity were clarified using biochemical tests. Next, minimum inhibitory concentration (MIC) of Cd and Ni determined for these bacteria. Following preparation of alive and deactivated bacteria and solutions containing equal amounts of N and Ca, the levels of Ni and Ca were determined using atomic adsorption system to evaluate the levels of biosorption and bioaccumulation.
The microorganisms isolated in this study belonged to Bacillus sp., Staphylococcus sp. and Actinomycete sp. Among them, Actinomycete sp. showed the highest absorption activity for these elements. The bioaccumulation was higher than biosorption at low concentrations of the metals but the biosorption was dominant at high pollution levels. In both systems, the bacteria showed higher ability for remediation of Cd in comparison to Ni.
The bacteria in the soils polluted to heavy metals showed intensive resistance activity to high concentrations of the elements. Both bioaccumulation and biosorption methods were suitable enough to remediate these metals in aquatic environments. However, the bioaccumulation was more powerful than the second method at low concentrations of the metals whereas biosorption showed more ability at high concentrations of the metals.