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Characteristics of Leachate Generated at Landfill Sites and Probable Risks of Surface and Groundwater Pollution in the Surrounding Areas : a Case Study of Matuail Landfill Site, Dhaka

MD. AZIM
Department of Soil, Water and Environmental, Dhaka-1000, Bangladesh

M. MAHABUBUR RAHMAN
Department of Soil, Water and Environmental, University of Dhaka, Dhaka-1000, Bangladesh

RIAZ HOSSAIN KHAN
Department of Environmental Science & Disaster Management, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh.

A.T.M.M. KAMAL
Department of Soil, Water and Environmental, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

The characteristics of leachate and its probable risks on surface and groundwater pollution were investigated following the analysis of some chemical parameters of the leachate generated in the Matuail landfill site, Dhaka, Bangladesh. The laboratory test results on untreated grab leachate samples show high concentration of TDS (734 ppm), COD (1631 ppm), NH₄ +-N (1253 ppm), HCO₃ - (27962 ppm) and certain heavy metals such as Ni (1.05 ppm) and Cr (0.74 ppm) and have very high potential for contaminating ground and surface water. Biological treatment through aeration and sedimentation improves the quality of leachate significantly. However, parameters such as COD (1437 ppm) are found to be still high even after treatment. The surface water samples around the landfill site appear to be contaminated, most probably, through the overflow of leachate. Groundwater parameters, however, satisfy drinking water quality standard except, the concentration of NH₄ +-N (maximum 74.2 ppm) and K (maximum 25 ppm).

Keywords: Leachate; Pollution; Solid waste; Landfill

Location: Department of Soil, Water and Environmental

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Contamination

Objectives:

The present investigation aims at analyzing some chemical parameters such as chemical oxygen demand (COD), ammonium (NH4 + -N), nitrate (NO₃ – -N), carbonate (CO₃ 2- ), bi-carbonate (HCO₃ -), calcium (Ca²+ ), calcium and magnesium (Ca₂++Mg₂+), chloride (Cl¯), lead (Pb), nickel (Ni), zinc (Zn) etc. in the leachate, ground and surface water and investigate its link to pollution, if any.

Methodology:

For the present study, two leachate samples were collected (untreated and treated) from the north side of landfill. Untreated leachate sample was collected from the internal roadside drain located at 90º27.118'E and 23º43.190'N. Treated leachate sample was collected from a treated pond located at 23º43.208'N and 90º27.118'E. Grab water samples were collected for surface water quality analysis from two ponds used for fisheries located at southern and eastern side of the landfill. Surface water-1 (SW-1) was collected from the location at 23º43.223'N and 90º27.118´E and surface water-2 (SW-2) was collected from the location at 23º42.962'N and 90º27.012'E. Groundwater samples (GW-1, GW-2, GW-3 and GW-4) were collected from specific wells only after it has been pumped sufficiently to ensure that the samples represent the groundwater that feeds the well. GW-1 was collected from a hand tube-well located at 23º43.223'N and 90º27.181'E, which was mainly used to analyze groundwater quality of the landfill site at a depth of about 115 feet. GW-2 was collected from a drinking water deep tube-well (about 400 feet in depth) located at 23º43.017'N and 90º26.996'E. The other deep tubewell (418 feet in depth) water sample, GW-3 was collected from the location at 23º42.961'N and 90º27.013'E. GW-4 was hand tube-well water at a depth of about 130 feet located at 23º42.12´N and 90º27.15´E. During samples collection, 250 ml PVC sampling bottles for leachate and 125 ml PVC sampling bottles for surface and groundwater were used. For laboratory analysis, four bottles each of treated and untreated leachate samples, and 20 bottles each of surface water and ground water samples were collected. During sampling, sample bottles were rinsed 2-3 times with the water being collected, and 0.45 µm membrane filter was used to remove unwanted particles from the water samples. To prevent the loss of certain cations such as Cd, Cu, Cr, Ni and Zn and so forth by adsorption, or ion exchange with the walls of glass containers, some sampling bottles were acidified with concentrated HCl or HNO₃ to pH below 2.0 and the other were un-acidified and used to analyze for anions. Samples collected were carefully transported to the laboratory located at the Department of Soil, Water and Environment, University of Dhaka and were preserved in refrigerator under appropriate environment to prevent precipitation of heavy metallic ions before chemical analysis. A GARMIN 12 channel GPS was used to record the geographic locations of the sampling points. Electrical conductance (EC), total dissolved solid (TDS), dissolved oxygen (DO) and pH were recorded for each sample on the spot using portable EC meter (Hanna-Germany), TDS meter, DO meter and pH-meter (HannaGermany), respectively. The quantitative analysis was carried out for most of the chemical parameters of collected samples involving volumetric, colorimetric and atomic absorption spectrophotometer method. Parameters such as COD, CO₃ 2– , HCO₃ – , Ca²+ , Ca2+ , Mg₂+ etc. were determined by the volumetric chemical analysis procedure whereas heavy metal contents of all samples were determined by using atomic absorption spectrophotometer. K and Na contents were determined using flame photometer.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 35, No. 2, 153-160, 2011

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The risk of pollution of surrounding lowlands (used for agriculture and fisheries) is particularly high during the wet season, when such flow of drainage water/leachate would be much higher. So management of untreated leachate should be made more carefully in the studied area especially during rainy season. The deeper aquifer lying beneath the Dhaka city is the primary source of potable water for the population of Dhaka although the piezometric surface goes much lower compared to the previous years due to higher abstraction rates and insignificant amount of recharge in the urban area. The landfill site is however, not likely to pose any threat to the water quality of the main aquifer, which is located at a depth of about 60 to 70m below ground surface and is overlain by a thick clay layer. The shallow aquifer around the project site is not widely used for supply of water for domestic use, therefore, possible public health risks from contamination of the shallow aquifer is also not significant. It may be due to the higher travel time required by the leachate to reach the shallow aquifer compared to the time required for complete degradation of leachate. Hence, the risk of groundwater pollution is very low, provided the clay layer is continuous and no fracture is present through this overlying clay layer. Under the present situation, the best option is to continuously monitor the quality of shallow groundwater around the project site and proper geophysical investigation should be carried out for the identification of possible leakage in a regular basis.

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