<![CDATA[Leachate generated from landfill disposal sites poses a serious environmental threat due to its high content of organic pollutants and heavy metals. Elevated levels of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and lead (Pb) may contaminate soil and surrounding water bodies if the leachate is not properly treated. Phytoremediation using water hyacinth offers an eco-friendly and low-cost alternative for leachate treatment. This study was conducted to evaluate the effectiveness of water hyacinth in reducing COD and BOD concentrations and removing Pb from leachate. An experimental method with a batch reactor system was applied, using 30 clumps of water hyacinth in each tank and contact time variations of 7, 14, and 21 days. COD, BOD, and Pb concentrations were measured before and after treatment using standard water quality analysis methods. The results showed that the 21-day contact time produced the highest removal efficiency. COD decreased from 1551.21 mg/L to 520.32 mg/L, representing a 66.44% reduction, while BOD decreased from 576.34 mg/L to 150.62 mg/L, equivalent to a 73.88% reduction. Pb concentration also decreased from 0.92 mg/L to 0.18 mg/L, with a removal efficiency of 80.43%. These reductions are attributed not only to the physiological activity of water hyacinth but also to the interactions among hydrological conditions, root zone architecture, and rhizosphere-mediated microbial communities, which collectively facilitate biodegradation, assimilation, and bioaccumulation of pollutants. Overall, the study highlights the critical role of integrating environmental geoscience principles with phytoremediation to optimize leachate treatment. Understanding the geochemical characteristics of leachate, subsurface hydrodynamics, and plant-microbe interactions provides a scientific basis for designing sustainable, low-cost, and efficient treatment systems. The findings indicate that water hyacinth can serve as a practical and geoscience-informed solution for mitigating organic and heavy metal pollution from landfill leachate, with 21 days identified as the optimum contact time.]]>
