| Summary: | Leachate is one of the most serious environmental hazards associated with landfills especially which are unlined and uncontrolled. Thus, this study aims to characterize and compare raw leachate from active landfills (Ulu Maasop and Kampung Keru) and closed landfill (Pajam), then subsequently quantify the potential leachate contamination from each landfill using Leachate Pollution Index (LPI). The results obtained from the current study were compared with data from previous publications and indicated higher physico-chemical characterizations, especially for BOD and COD, than that of the other similar landfill categories. Based on the current findings, the low ratio of biodegradability and slightly alkaline pH values in leachate samples indicated that the sites (both active and closed landfills) were characterized by methanogenic conditions. Moreover, heavy metal concentrations, Cr, Fe and Se levels were higher than the leachate discharge standards for all leachate sampling sites. The As, Cu, and Mn, also surpassed the leachate discharge standards for the active landfill sites tested in this study (Ulu Maasop and Kampung Keru landfills). Next, the LPI calculated for Ulu Maasop, Kampung Keru, Pajam (1 and 2) landfills were 15.28, 13.89, 12.91 and 11.51, respectively, all exceeding the LPI for discharge standard of 5.696. Based on the leachate characterizations and the LPI values, these landfills pose a significant threat to the environment through the dissipation of leachate to the surface and groundwater, especially with the presence of BOD, COD, As and Cr. Thus, remedial actions such as rehabilitation of such unlined landfills and post-closure monitoring are crucial for both active and closed landfills to ensure the generated leachate is stabilized. Such actions will reduce and control the threat to the environment.
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