Monitoring and optimization of heavy metal phytoextraction in constructed wetlands amended with organic chelators

The present study was conducted in a lab-scale constructed wetland to investigate the extraction potential of Typha latifolia and Lemna minor for heavy metals (HMs) from tannery wastewater (TWW), supplemented with citric acid (CA) as a chelator. After 6 weeks of treatment, harvesting was followed by a recording of agronomical trait data. The data indicated a significant (p < 0.05) decline in the morpho-physiological and biochemical attributes of the plants, which correlated increase in TWW concentration. Maximum accumulation of selected HMs including chromium (Cr), cadmium (Cd), and lead (Pb), in L. minor was observed at 100% TWW, with respective values of 148.4%, 129.4%, and 85.6% as compared to 25% TWW. In T. latifolia, a significant increase in Cr (143.8%), Cd (148.3%), and Pb (126.8%) in the roots was also observed at 100% TWW as compared to 25% TWW. CA amendment under TWW conditions significantly enhanced Cr uptake in L. minor by 61% and accumulation by 94%. Similarly, in the roots of T. latifolia, Cr uptake was elevated by up to 11%, with accumulation increasing by 117%. These findings indicate that phytoextraction of heavy metals can serve as an efficient strategy for the remediation of tannery wastewater using Lemna minor and Typha latifolia in constructed wetlands.