Evaluation of the remediation potential of ethanolic leaf extracts of chromolaena odorata, azadirachta indica, and persea americana on the physicochemical quality of landfill leachate

Abstract

Landfill leachate is a highly contaminated wastewater generated during the decomposition of municipal solid waste and is characterized by elevated concentrations of organic matter, dissolved salts, nutrients, and other physicochemical pollutants that pose serious environmental and public health concerns. This study evaluated the effectiveness of ethanol leaf extracts of Persea americana, Chromolaena odorata, and Azadirachta indica, applied individually and in different combinations, for the remediation of the physicochemical properties of landfill leachate. Fresh leaves of the three plant species were collected, washed, air-dried, pulverized, and extracted using ethanol following standard extraction procedures. The extracts were applied individually, as binary combinations, and as a ternary combination at concentrations of 1, 2, and 3 mg/mL. Treated leachate samples were analyzed for selected physicochemical parameters, including electrical conductivity (EC), total dissolved solids (TDS), turbidity, total hardness, biochemical oxygen demand (BOD), chemical oxygen demand (COD), chloride, sulphate, nitrate, nitrite, calcium, magnesium, phosphate, and potassium using standard analytical methods. Data were subjected to analysis of variance (ANOVA), and treatment means were separated using the Least Significant Difference (LSD) test at a 5% level. The results showed that all plant extracts significantly (p < 0.05) improved the physicochemical quality of the landfill leachate compared with the untreated control. Increasing extract concentration from 1 to 3 mg/mL resulted in progressive reductions in EC, TDS, turbidity, total hardness, BOD, and COD, indicating a concentration-dependent remediation effect. Among the single-plant treatments, Persea americana consistently exhibited the highest remediation efficiency, whereas Chromolaena odorata showed comparatively lower performance at the lowest concentration but improved markedly as the dosage increased. Binary combinations generally outperformed individual extracts, while the ternary combination of Persea americana + Chromolaena odorata + Azadirachta indica produced the greatest overall improvement in leachate quality. The findings demonstrate that ethanol leaf extracts of Persea americana, Chromolaena odorata, and Azadirachta indica, particularly when applied in combination, are effective natural remediation agents for improving the physicochemical quality of landfill leachate.