Heavy metals and nutrients removal in a batch-fed greywater treatment system planted with Canna indica and Oryza sativa L.

Abstract

The objective of this investigation was to determine whether Canna indica and Oryza sativa L. plants have the phytoremediation potential for removing heavy metals and nutrients from greywater treated in batch-fed Horizontal sub-surface Flow Constructed Wetlands (HssFCW). The HssFCW had a Hydraulic Retention Time (HRT) and organic loading rate (OLR) of 3 days and 3.96 (g.BOD/m².day) respectively. Greywater (GW) samples were characterized for electrical conductivity (EC), total nitrogen (TN), total phosphorous (TP), pH, sodium adsorption ratio (SAR), metals (Al, Fe, Mg, Ca) and Biochemical Oxygen Demand (BOD₅). The accumulation of metals in the soil and edible parts of plants was evaluated in terms of bioconcentration and translocation factors. Metal concentrations were determined using an atomic absorption spectrometer, while nutrients were by colorimetric method. The result shows that the metals and nutrients were below the WHO allowable limit for treated greywater recycling in agriculture. Nutrient removal was insignificantly different while metal removal was significantly different in the constructed wetlands (CW). The results indicated that C. indica is preferred as a perennial plant with unlimited metal accumulation and high nutrient removals compare to O. sativa L. with a high metal concentration in the above-ground plant tissue and also an annual plant.

Keywords:

• Canna indica
• greywater
• heavy metals
• nutrients
• Oryza sativa L.
• phytoremediation

Acknowledgments

We thank the laboratory staff and assistants for their commitment. We gratefully acknowledge the critical comments and corrections of respected reviewers whose comments and corrections improved this work considerably.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article. Raw data are also available from the corresponding author on request.

Additional information

Funding

The authors reported there is no funding associated with the work featured in this article.