Comparative study of landfill leachate characteristics and their influence on groundwater: global perspectives

Improper solid waste management, particularly the disposal of untreated municipal waste, poses a major global challenge. One critical consequence is the generation of landfill leachate (LL), which can severely impact the ecosystem and human health. This review article covers the physiochemical characteristics of LL around the globe. Considerable variation exists in Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) levels. Municipal sanitary landfill in Greece recorded extremely high organic pollution load whereas Nkolfoulou landfill in Cameroon, Africa reported much lower levels of organic pollution load. pH values differ significantly, ranging from highly alkaline conditions in Havana, Cuba and acidic conditions at Kingtom dumpsite in Sierra Leone. An overall assessment of differences in the level of pollution is done by using the Leachate Pollution Index (LPI) and the Water Quality Index (WQI) shows great variability around the world. LPI values range from 42.18 at Okhla landfill, New Delhi, India to 5.43 at Wroclaw landfill, Poland. WQI values exhibited even greater disparity, with an exceptionally high 880.29 at Oti-Dompoase landfill while Kumasi, Ghana, compared to just 8.01 at Hryniewicze landfill, Poland. This review article also analysis the different pollution index models such as Health Quotient (HQ), Carcinogenic Risk Effect (CRE), or Pollution Load Index (PLI), which are practiced in different landfills across the globe and uses statistical techniques like Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) for the tracking of pathways and identification of source of pollution in LL around the world. The nature-based treatment methods such as wetlands, phytoremediation, and biofiltration in landfills are also mentioned in this review paper. Policy implications emphasize the need for clear regulatory frameworks, investment in appropriate nature-based treatment process, and regular monitoring of LL to ensure safe and sustainable LL management.