Assessment of the impact of landfill leachate on groundwater and surrounding surface water: a case study of Mekelle city, Northern Ethiopia

The aim of this study is to investigate the impact of leachate from municipal solid waste to groundwater and surface water quality surrounding the landfill site in Mekelle, Northern Ethiopia. The landfill is situated in carbonate geological formation where the effect of uncontrolled leachate release into the environment is evident at short distance of the site. The analysis of leachate sample showed elevated electrical conductivity (5280 μS/cm), chloride (256 mg/l), nitrate (92.6 mg/l) COD (1208 mg/l) and BOD (483 mg/l) in dry period. Samples of stream and groundwater in the vicinity of the landfill are characterized by high concentrations of TDS, bicarbonate, sulphate, chloride and nitrate. The elevated levels of these ions are attributed to seepage of landfill leachate with considerable input from local geology. The impact of leachate on water resources appeared to be higher in wet season when contaminant dispersion is accelerated by maximum infiltration and surface runoff. The elevated total dissolved solid and nitrate levels have proved that the water quality is unreliable for domestic water supply. Moreover, BOD (1.9–7.5 mg/l) and COD (42–160 mg/l) concentrations in the water samples were found to be exceeding the typical normal ranges, and were significantly higher in the surface water compared to the groundwater. This study highlights the need of leachate treatment mechanisms as remedial measures to prevent water pollution.