Assessment of bioremediation potential of Microcystis aeruginosa for removal of cadmium and lead ions from aqueous matrices

Capability of cyanobacterium, Microcystis aeruginosa, in the removal of cadmium and lead ions was investigated which was obtained after isolation from wastewater stabilization pond effluents. Influence of operational parameters including metal concentrations, pH, temperature and biomass dosage on removal efficiency was investigated. Also, applicability of closed reflux techniques for the digestion of cyanobacterial pellet was studied. A multi-phase washing method was developed in order to attain more elevated desorption efficiency. ۱-۵ washing cycles were repeated consecutively by the addition of new EDTA solution (۴mM), stirring on mixer and centrifugation for each cycle. Maximum removal efficiency occurred at pH ۷, temperature ۲۸°C and biomass dosage of ۰.۲g for Cd۲+ and corresponding values of ۶, ۲۵°C and ۰.۱g for Pb۲+. In all tested concentrations of Cd۲+ and Pb۲+, extracellular absorption overweighed intracellular uptake with highest ratio of the former to the latter of ۱۷۲ for Cd۲+and ۱۴۳ for Pb۲+. EC۵۰ values attained for Cd۲+and Pb۲+were ۲۰ mg L-۱ and ۱۵ mg L-۱, respectively. The closed-reflux digestion method was found as a suitable choice for cyanobacterial pellet digestion. Three-stage consecutive washing procedure devised in our study gave desorption efficiencies of ۹۲ and ۸۶ percent for Cd۲+ and Pb۲+ respectively as compared with values of ۵۲ and ۴۴ percent for Cd۲+ and Pb۲+, respectively obtained by the conventional washing procedure. This investigation verifies the possibility of employing M. aeruginosa for removal of Cd۲+ and Pb۲+ from aqueous and wastewater solutions.

Keywords:

Bioremediation , Cadmium , Lead , Microcystis aeruginosa