Cr, Ni, and Zn removal from landfill leachate using vertical flow wetlands planted with Typha domingensis and Canna indica

Abstract

Chromium (Cr), Nickel (Ni), and zinc (Zn) removal from landfill leachate using mesocosm-scale vertical flow wetlands, the effect of recirculation, and the ability of macrophytes to retain metals were evaluated. Wetlands were filled with coarse sand and light expanded clay aggregates and planted with Typha domingensis or Canna indica. Wetlands were operated using intermittent loading, with and without recirculation. Raw leachate was diluted and spiked with metals to reach the following concentrations: 0.2 mg L⁻¹ Cr , 0.2 mg L⁻¹ Ni, and0.2 mg L⁻¹ Zn and 1.0 mg L⁻¹ Cr, 1.0 mg L⁻¹ Ni, and 1.0 mg L⁻¹ Zn. Wetlands planted with T. domingensis presented higher metal removal than those planted with C. indica. Recirculation enhanced metal removal efficiencies significantly, being for T. domingensis/C. indica: 60/54, 49/47, 61/47% for Cr, Ni, and Zn at 0.2 mg L⁻¹, and 80/71, 76/62, 73/59% for Cr, Ni, and Zn at 1.0 mg L⁻¹, respectively. Metals were efficiently retained by macrophytes. Plant biomass and metal concentrations in roots were significantly higher than in shoots. Scanning electron microscopy and X-ray microanalysis showed that metals were absorbed by internal root tissues. A hybrid wetland planted with T. domingensis may be implemented to improve not only metal but also chemical oxygen demand and total nitrogen removals.

Novelty statement

Landfills generate leachate that contains a wide range of contaminants in concentrations that vary over time. Even when a landfill ceases to receive solid waste, the leachate will continue to be generated for years. To avoid environmental impact, such leachate should be treated. This work evaluated chromium (III), nickel (II), and zinc (II) removal from landfill leachate using vertical flow wetlands (VFWs) at mesocosm-scale. The performance of wetlands planted with Typha domingensis or Canna indica, and with and without recirculation were compared. VFWs have demonstrated to be efficient for landfill leachate treatment. At a global scale, studies on metal removal using this type of wetlands are scarce. Despite the advantages of treatment wetlands in Argentina (easy operation and maintenance and usual large availability of land inside factories), they are scarcely implemented.

Keywords:

• Wastewater
• contaminant
• removal efficiency
• macrophytes
• treatment wetlands

Acknowledgments

The authors thank their funding sources.

Additional information

Funding

This study was finaincially supported by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Litoral (UNL)-CAI + D Project and Agencia de Promoción Científica y Tecnológica, Convenio SAT CEAMSE-UNL.