Hydrochemistry and natural attenuation of leachate from tropical landfills

Landfilling, as a system to discard municipal waste, is still widely used in the tropics, often without appropriate protection against pollution of its surroundings. Leachate generation from landfills, and its chemical composition, varies widely and is significantly influenced by landfill geometry, the type and age of waste, seasonal precipitation, moisture and temperature. In the tropics, climate conditions vary strongly with seasons and need to be taken into account with regard to leachate management. A combination of physical, chemical and microbial processes can contribute to the attenuation of pollution by landfills, but further understanding of these processes is essential in order to allow for better management of landfills. This study focuses on several aspects: (a) the characteristics of landfill leachates, their seasonal changes and the impact on surface and groundwater pollution around the landfill, (b) the microbe-mediated nitrogen transformations and phenol degradation in landfill leachate and (c) seasonal changes in microbial communities in landfill leachate and assessment of their contribution to natural attenuation. Chapter 1 provides a general introduction on solid waste management, with special emphasis on solid waste management practices in Indonesia, and its association with social aspects. Also, it describes the general characteristics of leachate, and the hydrochemistry parameters that are often used for characterization and evaluation. Microbiological aspects of leachate generation and attenuation, particularly nitrogen transformation and biodegradation of phenolic compounds, are introduced. The location of research sites investigated in this study, research questions and methodological strategies are presented in this chapter. In Chapter 2, the surface landfill runoff from the Jatibarang landfill, near Semarang, and its impact on a nearby river has been studied to understand seasonal landfill leachate characteristics and to determine the occurrence of natural attenuation. The potential for attenuation and the contribution by biodegradation along the flow path to the river was determined by measuring monthly a range of leachate parameters, such as organic matter content and redox-related components. The results showed that the composition of leachate was greatly influenced by season. Electrical conductivity and concentrations of BOD, COD, organic nitrogen, ammonia, sulfate and calcium during the dry season were higher (up to 2.3-fold) than in the wet season. The residence time of waste-water in a leachate collection system at the site was less than 70 days. Field measurements showed that during this period hardly any biodegradation of organic matter and ammonia occurred (less than 25%). However, the potential for biodegradation of organic matter …