The removal efficiencies and mechanisms of Pb, Cr, Cd and Zn removal were investigated in batch type constructed wetlands
comprising water hyacinth (Eichhornia crassipes (Mart.) Solms) using a mass balance analysis. This study was conducted
for 15 weeks in four 590 l capacity tanks containing 3.1, 5, 0.2 and 1.1 mg/l of Pb, Cr, Cd and Zn respectively. Removal
efficiencies from the wastewaters were in the range of 92.1-99.6%, 31.3-100%, 46.3-94.4% and 25.1-94.8% for Pb, Cr, Cd
and Zn, respectively. The results showed that water hyacinth roots play a crucial role in the removal of Pb and Cr by means
of precipitation, though phytoremediation was insignificant. However, phytoremediation through rhizofiltration seemed to
govern the removal of Cd and Zn. We conclude that constructed wetlands comprising water hyacinth is a promising low
cost option for removing the above heavy metals within the ranges investigated
