Long-term Temporal Variations in Characteristics of Leachates from a Closed Landfill in an Arid Region

Abstract

There is limited information on the effect of characteristics of soil in the arid regions on the transport of pollutants. Al-Qurain landfill site is located about 1.5 km from the Arabian Gulf shoreline in Kuwait. The site was operated as an open dump and was designed without a liner or leachate collection system. This study was performed after 35 years of the site closure to investigate the quality of soil, leachate, and groundwater in its vicinity. A total of 25 test boreholes and 17 observation wells were used for the investigation. Analysis of soil, leachate, and groundwater samples shows high concentrations of organics (COD), nutrients (nitrogen, phosphorus), heavy metals, and minerals. Aging of the landfill has its impact on performance of landfill which was reflected on the characteristics of soil, leachate, and groundwater. The principal pollutants in leachate were COD, ammonia, and heavy metals as landfill age increased. A good indicator of landfill aging was the very low (0.04) BOD/COD ratio and BOD decay rate constant of 0.027/year. Water samples were also heavily polluted and their organic content ranged between 9 and 255 mg/L as BOD and 38 and 15,052 mg/L as COD. Solids levels in the water samples from the observation wells were generally higher than those typically reported in groundwater. The results showed that the mobility of the heavy metal was largely element-dependent. The organic content of the landfill played an important role in such mobility. This suggests segregation of waste disposed in landfills and replacing the open dumps by sanitary landfills to avoid such high long-term pollution that affects the site rehabilitation plans.