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

Abstract

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