Long-Term Characterization of Landfill Leachate: Impacts of the Tropical Climate on its Composition

Abstract

The disposal of Municipal Solid Waste (MSW) in sanitary landfills produces leachate, whose composition changes depending on the microbial community and the environmental conditions. However, these changes cannot be observed in sanitary landfill because of the superposition of cells, which makes it difficult to determinate the relationship among the phases of biodegradation of MSW, the composition of the leachate and the time required for complete stabilization of the waste. This illustrates the importance of building experimental cells that simulate landfill to monitor the leachate over a long period. This study aimed to analyze the composition of the leachate generated from an experimental cell built on the Delta A sanitary landfill of Campinas City, Brazil, over 945 days. The leachate showed a transition from an acidic anaerobic phase to a methanogenic phase within approximately 100 days. By the one-hundredth day, the leachate showed a characteristically low pH, between 5.0 and 6.0 and a high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) such as a young leachate with high biodegradability. Moreover, there was an intense leaching of the metals Cd, Fe, Pb and Mn, with concentrations higher than those allowed for the release in water bodies, according to Brazilian law. After the one-hundredth day, the leachate was characterized as stabilized. The pH increased and the concentration of volatile fatty acid, COD and BOD decreased. Co, Zn, Ni and Cu were leached. The potentially toxic metal concentrations found in the leachate also were above the values allowed by Brazilian law.