SIMULATION OF CONTAMINANT TRANSPORT FROM LANDFILL SITE: A CASE STUDY OF OKHLA LANDFILL

Abstract

India is the second fastest growing economy and the second most polluted country in the world. Delhi, capital of India, generates approximately 7,000 metric tons of MSW daily. At present, there are three landfill site in Delhi – Bhalsawa, Gazipur, and Okhla. All the three are unlined and fall under the category of uncontrolled solid waste disposal facility. The leachate generated mostly percolated down the ground surface and the excess quantity gets collected in some low lying areas and sometimes gets mixed up with sewer and drainage systems thereby polluting groundwater and surface water sources. To protect the groundwater from contamination, it is quite essential to provide the bottom barrier of suitable thickness. The present study was undertaken to determine the rate of movement of potential contaminants from the bottom of the landfill, to achieve this mathematical model was formulated to express the mass transport of contaminants from a landfill due to the migration of leachate. Various mechanism of contaminants migration from the bottom of landfill was taken into account. The solution of model in the form of concentration profile of potential contaminants below landfill was obtained using the explicit Finite Difference Method (with upwind correction) implemented in MatLab 7.0. Model developed in this study was validated for two parameters of field data estimated by T.L.T. Zhan et al. 2014 were used for an uncontrolled landfill at Huainan, China. Landfills are an indispensable part of everyday living, they may pose a long-term threats to groundwater as well as surface waters that are hydrologically connected. In the recent decades, groundwater resources have become increasingly threatened by the leaching of contaminant from uncontrolled landfills, containing industrial and household waste. The present study was conducted at Okhla landfill site having high concentration of chloride, iron and some heavy metals. The impact of this concentration to the underlying groundwater over the period of time is determined by sampling and analysis of leachate and groundwater from nearby locations. This concentration was found to be in a consonance with the simulated concentration with chloride in ground water considering one dimensional transport model. Analysis of model results was carried out to determine the impact of model parameters i.e. time period of simulation, equivalent height of leachate, depth on the transport of contaminant from Okhla landfill. The observed concentration is simulated with the concentration of chloride at 120 m radial distance from Okhla landfill site.