Modeling of Heavy Metals Removal from Municipal Landfill Leachate Using Living Biomass of Water Hyacinth

Abstract

Water Hyacinth, Eichhornia crassipes, a fast-growing floating aquatic macrophyte; was used for the removal of heavy metals from a municipal landfill leachate. The leachate was spiked with different mixtures of five heavy metals (Cd, Cr, Cu, Pb and Ni), at a range of concentrations to cover the ranges reported in literature. The initial concentrations of the total heavy metals in leachate ranged from 0.06 to 5.5 mequiv L⁻¹. All experiments were carried out in batch reactors in a greenhouse environment. The water hyacinth plants showed a very promising ability to remove and accumulate these metals from the leachate (24% to 80% removal of total heavy metals).

Generally, the reduction in concentration of total heavy metals followed two distinct patterns, a rapid initial decrease followed by a slower decrease. An exponential mathematical model was established to estimate the remaining concentration of total heavy metals in the leachate over time for the rapid initial decrease. Also, a linear relationship was established to estimate the concentration of total heavy metals over time for the slower decrease. In addition, Langmuir and Freundlich isotherms were applied to the observed data and the constants of each isotherm were obtained.

KEY WORDS:

• Eichhornia crassipes
• Langmuir isotherm
• Freundlich isotherm
• exponential model

ACKNOWLEDGEMENT

The author gratefully acknowledges the advice and help received from Dr. J.K. Bewtra, Professor Emeritus and Dr. N. Biswas, Professor, Department of Environmental Engineering, University of Windsor, Windsor, Canada. The assistance received from Dr. Barbara Booth, the assistant editor for the Journal of Environmental Science & Technology, University of Iowa, Iowa City, IA, USA, in copy–editing this manuscript is highly appreciated.