Effects of raw and treated landfill leachate on the chemical properties of a Tunisian soil

Abstract

Landfill leachate (LFL) is a polluted effluent generated during the decomposition of organic wastes. Because it is rich in organic matter and nutrients, LFL can be used as an agricultural fertilizer, especially in arid and semiarid areas. In this context, the aim of this study was to evaluate the effects of LFL on the chemical properties of soil when LFL is used as a soil fertilizer. Leachate samples were collected from the Sfax landfill site in Tunisia, which has an area of 35 ha and receives 500 tons per day of solid wastes. Sandy soil was taken from an agricultural region of Sfax. Different treatments based on doses of 50, 80, and 100 m3/ha of raw and Fenton-treated leachate were added to the soil. The results showed that leachate amendment modified the chemical properties of the soil, which in turn depended on the concentration of the raw or treated LFL applied. The electrical conductivity of the soil increased significantly upon leachate addition, reaching values > 2 mS/cm. A decrease in the soil pH and an enrichment of the soil with nutrients were also observed. The organic matter content of the soil increased by 0.3% and 0.24%, respectively, following treatment of the soil with 100 m3 of raw and/or treated leachate. A dose of 50 m3/ha of raw leachate increased the level of potassium by 0.2 mg/g. The soil nitrogen level increased from 0.07% in control soil to 0.15% in soil treated with 100 m3/ha of raw leachate. These results indicate that treatment with leachate improves soil fertility but can cause salinization if too much leachate is applied.