Removal of COD and Colour from Sanitary Landfill Leachate by using Coagulation

This study investigated two methods for the removal of COD and colour from sanitary landfill leachates. The first method involved the use of coagulation/flocculation process using FeCl3 as a conventional coagulant and Ca(OH)2 as base-precipitant. The second method involved integration of Fenton’s reagent into the coagulation/flocculation process. Concentration of FeCl3 that reduced chemical oxygen demand (COD), and color by 37 and 62% is 1000mg/l. Fenton-coagulation flocculation process reduced the COD and color of the leachates by 88 and 98% respectively. The optimum conditions for the effectiveness of Fenton’s reagent, namely temperature, pH, H2O2 and coagulant dose were studied. @JASEM Landfill leachate from municipal solid waste landfill sites are often defined as hazardous and heavily polluted wastewaters. The leachates may contain a large amount of organic matter (both biodegradable and biorefractory carbon), ammonia-nitrogen, heavy metals, chlorinated organic and inorganic salts (Wang et al., 2002). The discharge of landfill leachate can lead to serious environmental problems as they may percolate through soils and sub soils, causing extensive pollution of ground and surface waters if they are not properly treated and safely disposed (Tatsi et al., 2003). Landfill leachate treatment by several methods namely coagulation flocculation (Tatsi et al., 2003; Amokrane et al., 1997); coagulation photo oxidation (Wang et al; 2002); nanofiltration (Marttinen et. al, 2002); biological treatment and combined physico-chemicalnanofiltration process (Treboutet, et al. 2001) have been reported. FeCl3 is a widely used coagulant and it has been used for the removal of organic matter in landfill leachates (Tatsi et al., 2003) and industrial wastewater (Peres et al., 2004; Amoo et al., 2004). Fenton’s reagent (hydrogen peroxide in the presence of a ferrous salt) has been used for the treatment of both organic and inorganic substances under laboratory conditions as well as real effluents from different resources like chemical manufacturers, refinery and fuel terminals, engine and metal cleaning etc. (Gogate and pandit, 2004). The process is based on the formation of reactive oxidizing species, able to efficiently degrade the pollutants of the wastewater stream (Bossman et al., 1998; Pignatello et al., 1999). In the oxidation system, three reactive species are involved; two of them involve the presence of hydroxyl radicals (classical Fenton’s chemistry) in either ‘free’ or ‘caged’ form, whereas third oxidant has been postulated to be aquo or organo-complexes of the high valence iron, the ferryl ion (Gogate and Pandit, 2004). The oxidation system can be effectively used for the destruction of toxic wastes and non-biodegradable effluents to render them more suitable for a secondary biological treatment (Perez et al., 2002 Martinez et al., 2003; Peres et al., 2004). Therefore, in the first phase of the present work, a coagulation/flocculation method is applied for COD and color removals from the landfill leachate, whereas, the second phase involves coagulation Fenton process for COD and color removal from the landfill leachate. The specific aim of this work was to study the relative effects of different operational schemes such as temperature, pH value, concentration of H2O2 and coagulant dose. MATERIALS AND METHODS Leachate sampling: The leachate was collected from Aboru Landfill site (Lagos, Nigeria). Characteristics of the leachate sample are as shown in Table 1. Table 1. Characteristics of landfill leachate sample