Sustainable Remediation of Heavy Metal–Contaminated Urban Lake Water Using Aquatic Macrophyte-Based Phytoremediation

Urban freshwater systems are increasingly threatened by physicochemical deterioration and heavy metal accumulation, driven by rapid urbanization and wastewater inflows. The present study evaluates the phytoextraction and rhizofiltration potential of three floating aquatic macrophytes—water hyacinth (WH), Pistia stratiotes (PS), and duckweeds (DW)—for improving the water quality of Halasuru Lake, Bengaluru, India. Baseline monitoring revealed elevated dissolved solids, organic pollution loads, microbial contamination, and trace levels of heavy metals, including Cd, Pb, Cr, Hg, Zn, and As. Short-term phytoextraction experiments demonstrated progressive reductions in electrical conductivity, total dissolved solids, alkalinity, hardness, COD, BOD, and pathogenic indicators, with duckweed exhibiting the highest remediation efficiency. Heavy metal concentrations declined systematically, with toxic metals showing significant attenuation. Long-term rhizofiltration conducted over 4 months resulted in approximately 45–50% reductions in major and trace metals, confirming sustained uptake by plant root systems. Comparative performance followed the order DW > PS > WH. The findings establish floating macrophyte-based remediation as a cost-effective, eco-friendly approach for restoring contaminated urban lake systems and highlight duckweed as a highly efficient candidate for large-scale water quality management.