Removal of zinc, lead and cadmium by water hyacinth (eichhornia crassipes)

Under the present investigation efficiency of the aquatic macrophyte Eichhornia crassipes was tested for the removal of selected heavy metals (Zn, Cd, and Pb) in laboratory conditions. The work also aims to characterize the associated micro flora of the rhizosphere system of the Eichhornia crassipes and wetland system where it grows naturally. Heavy metal content in water and water hyacinth from wetland system were also studied. The results revealed that the heavy metal concentration of the wetland water ranged from 0.01 to 0.05ppm, from 0 to 0.02ppm and from 0 to 0.05ppm for zinc, cadmium and lead respectively. The order of abundance of heavy metals in the water samples are Zn˃Pb˃Cd. The abundance patterns of heavy metals in leaf, petiole and root were Pb˃Zn˃Cd, Cd˃Zn˃Pb and Cd˃Zn˃Pb respectively. Six bacterial genera (Acinetobacter, Alcaligens, Bacillus, Kurthia, Listeria and Chromobacterium) were represented in rhizosphere of Eichhornia crassipes and 4 bacterial genera (Acinetobacter, Bacillus, Listeria and Chromobacterium) were recorded from associated water system. The phytoremediation studies revealed that Eichhornia crassipes removed appreciable amount of selected heavy metals during the experiment period. Hundred percentages of Pb and Cd were removed from the experiment tank during 6th and 12th day of the experiment respectively. 90% of zinc was removed during the end of the experiment. Results of the present study concluded that Eichhornia crassipes is a hyper accumulator of Zn, Cd and Pb from aqueous solution.