Monitoring leachate composition at a municipal landfill site in New Delhi, India

Most of the landfills in developing countries do not have any liner at the base, or a drainage layer or a proper top cover, which results in the potential problem of groundwater/surface water contamination due to the leachate. Hence, to decide whether the leachate is to be collected and treated, or may be allowed to discharge into the adjoining soil or public sewer or surface waterbody, it is essential to have an estimate of the amount of leachate and, more importantly, the composition and strength of the leachate and variation of leachate contaminants with time as the landfill site develops. In this paper, the experimental work carried out at one of the landfills in New Delhi, India, to ascertain the composition of leachate, and its effect on the groundwater in the existing situation is presented. The variation in the leachate composition with the age of deposition of solid waste has been studied. The study indicates that the leachate composition varies considerably with the age of deposition of the waste. It may be worthwhile to use different methods for the treatment of leachate from different parts of the landfill, if collected separately. It has also been concluded that since leachate contains high concentrations of organic and inorganic constituents, including heavy metals, liners must be used at the landfills. The presence of bore wells at landfill sites to draw groundwater threatens to contaminate the groundwater, and immediate remediation steps should be taken at all landfill sites that have groundwater bore wells.