Dr. Valdes-Morales, Hector

This study aims to investigate the feasibility to apply a coagulation-flocculation process to treat the landfill leachate of the municipal solid waste of Casablanca city (Morocco). Three types of coagulants are assessed: lime (Ca(OH)2), ferric chloride (FeCl3), and alum (Al2(SO4)3). Optimum conditions in terms of the removal of chemical oxygen demand (COD), heavy metals, colour and turbidity contents are determined, using a standard jar test apparatus. Optimum coagulant dosages of 52.5 g Ca(OH)2.l-1, 12 g FeCl3.l-1 and 22.5 g Al2(SO4)3.l-1 are obtained. Lime allows to remove 66.25% of COD, 98% of turbidity, 80% of colour with a low sludge volume generation (30%). When the optimum coagulant dose of FeCl3 is applied a 62.5% of COD, 92.5% of turbidity, 82% of colour are removed with less sludge volume generation (21%).Whereas when Al2(SO4)3 is used 11% COD and 6% of turbidity removal are obtained with a slightly lower sludge volume generation (11%). Regarding the analysis of metallic elements, the results show that a substantial elimination of heavy metals is reached, particularly of Cd, Cr, Cu, Fe, Ni and Pb. Treatment with lime shows a greater affinity to Cr (86%) and lower to Fe (60%). Ferric chloride allows to eliminate most of the detected metal elements with a high affinity toward Cd, Cu, Ni, Cr and Zn. Alum shows to be very suitable for Ni, Pb, Cr elimination with 95 %, 94 % and 93% removal efficiency, respectively. These results show that coagulation-flocculation could be used as a promising process for the pretreatment of landfill leachates of Casablanca city.

This article presents a combination of coagulation–flocculation and powder activated carbon (PAC) adsorption as a treatment process for landfill leachate. Leachates were collected from a municipal solid waste landfill in Mediouna site, Casablanca city. Ferric chloride (FeCl3) is used here as a coagulant to study the optimum conditions for the removal of chemical oxygen demand (COD), colour, total suspended solids (TSS) and turbidity in jar tests. This coagulant showed the highest removal efficiency in terms of COD (62.5%), turbidity (92.5%), colour (80%) and least sludge volume generation (30% v/v) for an optimum coagulant dose of 12 g Fe3+ L–1. Combining coagulation with adsorption process onto PAC enhances the removal of COD, turbidity and colour reduction by a 77%, a 99% and a 99.7%, respectively. These results show that coagulation-adsorption could be used as a promising hybrid process for the treatment of landfill leachates.