Leachate Quality Characteristics and Groundwater Contamination around Active and Closed Landfills in Lagos, Nigeria

Abstract

Landfilling is widely applied as a disposal method for solid wastes in most developed and developing countries. However, in many developing nations many landfills are not properly managed, and pose a serious threat to the environment due to leachate run-off. The risk of groundwater contamination by leachate is considered a significant environmental concern associated with landfilling. This study evaluated the quality characteristics of leachates from four landfills (two closed and two active landfills) in Lagos, Nigeria. The quality characteristics of groundwater samples near the landfills were also assessed. Leachate and groundwater samples were analyzed for some physicochemical properties, trace and major elements. The obtained results revealed that the total hardness in the leachates from all the landfills exceeded the regulatory limits in Nigeria. COD values in all the leachates were above the limit set by the Lagos State Environmental Protection Agency (LASEPA) which is an indication of gross organic pollution of the leachates. Generally, the concentrations of trace and major elements in the leachates were low. The presence of high concentrations of Pb in raw leachates of Abule-Egba (1.037 mg/L) and Olusoshun (1.680 mg/L) is a matter of concern because Pb is known to be one of the highly toxic environmental pollutants. Moreover, the total hardness level in groundwater near Soluos 3 landfill (190 mg/L) exceeded the limits by the Nigerian Standard for Drinking Water Quality (NSDWQ) and World Health Organization (WHO). Trace metals concentrations in the groundwater samples were generally low. Finally, the leachate quality characteristics of the closed and active landfills in this study and the associated groundwater quality characteristics did not follow any specific pattern but might have been largely influenced by the composition and type of solid wastes disposed at each of the landfill sites.

Keywords: Leachate, groundwater, landfill, physicochemical characteristics, trace and major elements, Lagos