Effects of landfill leachate on groundwater and its suitability for use

Landfill leachate is a noxious liquid with the potential to pollute groundwater resources following its horizontal and vertical mobilization from unsaturated to saturated zones. In this study, the characteristics of leachate from Roundhill landfill of South Africa were assayed using physicochemical analysis. Areal groundwater was sampled to assess the pollution capacity of leachate to the resource and the possibility of using it. Results showed that leachate had elevated levels of electrical conductivity, dissolved solids, cations and anions compared to the predefined standards by World Health Organization (WHO) and South African National Standards (SANS) for drinking water and its pH was 4.7. It was therefore not suitable for drinking and domestic use. In BH1, Ca²⁺, Mg²⁺, Fe and F⁻ surpassed WHO permissible limits while Fe, F⁻ and NO₃⁻ were above SANS standards for drinking and domestic water uses. In BH2, Fe levels were beyond both the SANS and WHO permissible levels. In BH3, Na⁺ and Fe were beyond both reference standards while Cl⁻ surpassed SANS permissible limits. Pollution of groundwater was associated with the characteristics of disposed solid waste at the facility, which decomposed to generate leachate that infiltrated into the resource. Sodium adsorption ratio showed a mild sodicity problem while elevated levels of Ca²⁺ in BH1 and Mg²⁺ in BH1 and BH3 pointed to hardness of the water, which impedes irrigation suitability. Frequent and extensive monitoring of areal groundwater was recommended as the movement of leachate was established to be slow and inconsistent over time.