INTRODUCTION

With rapid urbanisation and population growth municipal solid waste (MSW) generation in urban localities has increased many folds. Leachate, a liquid manifestation from MSW, has been considered as a serious pollutant affecting natural resources as surface and ground waters, human health and hygiene. It is a tainted liquid emanating from the bottom of the solid waste disposal facilities such as landfills that contains both soluble organic and inorganic compounds as well as suspended particles. The composition of landfill leachate depends upon the nature of solid waste buried, chemical and biochemical processes responsible for the decomposition of waste materials and total water content in waste (Fatta et al., 1999). A highly concentrated leachate is generated due to unscientific collection, segregation, and disposal practices of MSW. Dispersal of leachate poses a potential threat to soil and ground water quality (Jorstad et al., 2004; Chian and Dewalle, 1976). In developing nations like India especially the contamination problem is more serious, where the landfills do not have any leachate containment i.e. collection and treatment systems. Therefore, it is essential to adopt appropriate treatment/remedial measures to avoid contamination of the underlying soils and groundwater aquifers from the leachate generated from the landfills.

In India older landfills do not have a barrier system/liner and leachate collection system to restrict the migration of leachate into ground water. These landfills are often observed over permeable soils with shallow water tables beneath, enhancing the potential of the leachate to contaminate ground water. Presently there are no scientifi c leachate collection systems in India and other developing countries (Kumar and Alappat, 2005). Although the municipal solid waste (management and handling) rules 2000, Schedule III e Gazette 22(b) for specifications for landfill base clearly suggests leachate collection and treatment, leachate containment through 1.5 mm HDPE liner and provisions for storm water runoff gutters (MSW, 2000). In developed countries like Canada there are even stringent norms and regulations for leachate collection, containment, treatment and disposal that also emphasize regular monitoring of the surface and ground water in the vicinity of the landfill location (https://dr6j45jk9xcmk.cloudfront.net/documents/1110/ 66-landfill-standards-en.pdf).

In landfill leachate, numerous hazardous compounds as aromatics, halogenated compounds, phenols, pesticides, heavy metals and ammonium have been identified (Devare and Bahadir, 1994). This presses grave concerns about safety and health of human beings together with other aquatic life forms, impacting its ecology and food chains. Moreover, landfill leachate also imposes signifi- cant influence on the mobilization and attenuation through complexation of organic ligands and colloidal matters (Achankeng, 2004) in soil. Hence, it becomes imperative to assess the quality of leachate from MSW landfill. The physico-chemical environment and microbial communities play vital role in transformations of organic and inorganic compounds that helps in leachate decomposition and mineralization. This leads to the treatment of leachate. The presence of trace metals indicates toxicity in landfill leachate and its negative impacts on the growth of beneficial microflora that would have otherwise helped in leachate degradation and treatment. Morphological analysis of the microbial community is essential for identification and further characterization to determine the suitability of the microflora in the degradation of landfill leachate. Advanced tools as scanning electron microscopy (SEM) can be potentially used for rapid identification of the leachate microflora and enumeration (Mahapatra et al., 2014). Understanding various groups of bacterial and other microbial community aids in identifying dominant communities and potential to degrade leachate. These hosts of different bacterial microflora can be potentially used for the treatment of the leachate in-situ. Due to a heterogeneous mixture of municipal solid waste, various types of non-biodegradable organics are also present in landfill leachate. Thus pollution indices are essential for rapid assessment, monitoring and comparison of leachate quality (Kumar and Alappat, 2005). Presently the landfill leachate is gaining a serious attention in the developing countries and to a lesser extent in the developed world with relevance to its toxicity and harmful environmental externalities. This research paper attempts to characterize landfill leachate through physico-chemical, and biological analysis. A leachate pollution index has been developed for urban landfill localities that can be used as a tool for determining its quality and evaluates its contamination potential. This study also aims to serve as a guideline for the implementation of an appropriate leachate treatment technique for reducing adverse effects on the environment.