Thesis - faculty.ait.ac.th - Asian Institute of Technology

1.1 Background
Chapter 1
Introduction
Rapid industrialization and urbanization has resulted in an immense environmental
degradation. Population growth and poor environmental management practices have led to
deterioration of environmental quality in most of the developing countries. The
composition of the domestic refuse has radically changed in character over the last fifty
years, due to the rise of an affluent society. In recent years, solid waste management has
gained focus in many countries. Source reduction, reuse and recycling of waste,
composting, incineration and landfill disposal are few of the solid waste management
approaches practiced in different countries. The suitability of these approaches differs from
place to place. Municipal solid waste disposal in the landfill is the most common, cheap
and easiest municipal solid waste management practice followed throughout the world.
However, landfill requires a close environmental engineering surveillance in its design and
operation as it is likely to generate leachate which would potentially contaminate nearby
groundwater and surface water. With the changing nature of domestic refuse composition
over the years, the proportion of refuse available for decomposition has greatly increased
and thus the organic strength of the leachate has increased, resulting in its greater potential
to pollute water. A need exist to focus on the environmental problems concerned with
domestic landfill disposal to protect the environment and prevent adverse health affects.
Surface water that percolates through the landfill and leaches out organic and
inorganic constituents from the solid waste is termed leachate. Landfill leachate production
starts at the early stages of the landfill and continues several decades even after landfill
closure. Landfill leachate is mainly generated by the infiltrating water, which passes
through the solid waste fill and facilitates transfer of contaminants from solid phase to
liquid phase. Due to the inhomogeneous nature of the waste and because of the differing
compaction densities that will be encountered, water will be able to percolate through and
appear as leachate at the base of the site. If no remedial measures are taken to prevent
continual inputs of water to the wastes, this could pose adverse environmental impacts.
Landfill leachate is high strength wastewater which contains high concentrations of
organic matter and ammonium nitrogen. There is a fluctuation in the composition of
organic, inorganic and heavy metal components in the leachate making them more difficult
to be dealt with. The composition depends on the landfill age, the quality and quantity of
solid waste, the biological and chemical processes occurring in the landfill, and the amount
of precipitation and percolation. When the leachate containing high strength organic matter
and ammonia is discharged without treatment, it can stimulate algae growth through
nutrient enrichment, deplete dissolved oxygen, and cause toxic effects in the surrounding
water environment. Landfill design and operation have a major impact and influence on the
leachate generation. This leachate varies from landfill to landfill and over time and space in
a particular landfill with fluctuations apparent over short and long-term periods due to
climatic, hydrogeology and waste composition variations (Keenan, et al., 1984). Generally,
leachate contaminants are measured in terms of chemical oxygen demand (COD) and
biological oxygen demand (BOD), halogenated hydrocarbons and heavy metals. In
addition, leachate usually contains high concentrations of inorganic salts - mainly sodium
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