1. Introduction
Landfill leachate is wastewater emanated from sanitary
landfills treating a variety of municipal and industrial solid
wastes. Due to anaerobic conditions and long retention
time prevailing in sanitary landfills, landfill leachate normally
contains high concentrations of organic matters,
nutrients, pathogens and heavy metals which, if not properly
collected and treated, can cause serious pollution to
nearby surface and groundwater sources. The presence of
heavy metals at high concentrations in landfill leachate
usually causes toxic effects to microbes, making it difficult
to be treated biologically. Although several physical, chemical
and biological processes can be employed to treat landfill
leachate, for developing countries they can be expensive
in construction, operation, and requiring high-skilled labor
in operation. On the other hand, where land is available at
low-cost, natural systems, such as waste stabilization ponds
and constructed wetlands are attractive alternatives for
landfill leachate treatment.