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. 1-5 washing cycles were repeated consecutively by the addition of new EDTA solution (4mM), stirring on mixer and centrifugation for each cycle. Maximum removal efficiency occurred at pH 7, temperature 28°C and biomass dosage of 0.2g for Cd2+ and corresponding values of 6, 25°C and 0.1g for Pb2+. In all tested concentrations of Cd2+ and Pb2+, extracellular absorption overweighed intracellular uptake with highest ratio of the former to the latter of 172 for Cd2+and 143 for Pb2+. EC50 values attained for Cd2+and Pb2+were 20 mg L-1 and 15 mg L-1, 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 92 and 86 percent for Cd2+ and Pb2+ respectively as compared with values of 52 and 44 percent for Cd2+ and Pb2+, respectively obtained by the conventional washing procedure. This investigation verifies the possibility of employing M. aeruginosa for removal of Cd2+ and Pb2+ from aqueous and wastewater solutions.