Integrated Phytoextraction and Rhizofiltration for Heavy Metal Reduction and Water Quality Restoration in a Polluted Urban Lake

Urban freshwater ecosystems are increasingly threatened by physicochemical pollution, microbial contamination, and heavy metal accumulation, driven by rapid urbanization and untreated wastewater discharge. The present study investigates the efficiency of floating aquatic macrophytes—water hyacinth (WH), Pistia stratiotes (PS), and duckweed (DW)—for improving water quality and reducing heavy metal contamination in Hebbal Lake, Bengaluru, India. Physicochemical parameters, microbiological indicators, and heavy metal concentrations were systematically monitored during phytoremediation over 30 days, followed by long-term rhizofiltration assessment at monthly intervals from July to November 2025. Significant reductions in electrical conductivity, total dissolved solids, alkalinity, hardness, COD, BOD, and microbial load were observed, indicating substantial improvement in water quality. Heavy metals, including Al, As, Cd, Cr, Cu, Fe, Pb, Mn, Hg, Se, and Zn, exhibited progressive decreases during both the phytoextraction and rhizofiltration phases. DW demonstrated the highest metal uptake efficiency, particularly for Cd, Pb, Hg, Mn, Se, and Zn, followed by WH and PS. The combined application of phytoextraction and rhizofiltration offers a sustainable, low-cost strategy for restoring polluted urban lakes and mitigating heavy metal contamination.