Low-cost biomass for the treatment of landfill leachate from Fez City: application of a combined coagulation–adsorption process

In this work, the efficiency of a novel treatment of solid-waste landfill leachate based on coagulation and then adsorption onto a natural bioadsorbent was examined. The reduction in the chemical oxygen demand (COD), biological oxygen demand (BOD5), turbidity, and color of the leachate from the urban sanitary landfill in Fez City (Morocco) following treatment was evaluated. Ferric chloride was used as the coagulant in the coagulation–flocculation pretreatment of the leachate, and Cupressus sempervirens cones were employed to adsorb the contaminants in the coagulated leachate. The optimum dose of ferric chloride was found to be 20 g per liter. The resulting coagulation process reduced the COD by 69%, the BOD5 by 60%, and the color of the leachate by 88%. Following the adsorption of the pretreated landfill leachate on Cupressus sempervirens cones, the COD, BOD5, and color of the leachate were found to be 86%, 96%, and 93% lower than their original values, respectively. The adsorption capacity of the treatment qe was calculated as 385 mgO2g-1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{mg}}_{{{\text{O}}_{ 2} }} \;{\text{g}}^{ - 1}$$\end{document} for 1 g of Cupressus sempervirens cones per liter under optimal adsorption conditions (including pH 7, 25 °C, and 8 h of contact time). A study of the adsorption kinetics for the COD revealed that a pseudo-second-order model provided the best fit to the experimental kinetic data, and the equilibrium data were well described by the Langmuir isotherm model. These results of the study indicate that the novel combined coagulation–adsorption treatment of landfill leachate is an inexpensive alternative to current landfill leachate treatments, and is suitable for application to industrial-scale sanitary landfills.