Leaching ofMetals, Organic Carbon and Nutrients fromMunicipalWaste under Semi-Arid Conditions

Document Type: Original Research Paper


1 Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology, Sector H-12, Islamabad, Pakistan

2 Department of Crop and Soil Sciences,Washington StateUniversity, Puyallup,WA98371, USA


A large portion of municipal waste, disposed in landfills, is organic in nature. This organic
material starts decomposing soon after the disposal in landfills. The decomposition leads to the generation of
in situ leachate, and this leachate can contain substantial amounts of contaminants. Under arid conditions,
leachate is solely generated by waste decomposition, as little input of external water occurs due to rain. The
objective of this study was to characterize the in situ leachate from typical waste streams in Pakistan. We
collected fresh municipal solid wastes typical of household, mixed, and restaurant waste, and analyzed the
leachates for volume and water quality parameters. The wastes released up to 30% of their initial moisture as
leachate and the leachate contained metals, organic carbon, and nutrients at concentrations many times higher
than the environmental water quality standards for waste water discharge. As landfill leachate in Pakistan is
usually not contained or collected, the in situ leachate is a source of surface and ground water contamination.
Methods have to be developed and implemented to prevent leaching of contaminants into underlying soils and
sediments, and subsequently into ground and surface waters.