Pothential of leachate to leach cadmium from contaminated soil

Abstract

To study leaching potential of leachate to leach cadmium from contaminated soil. It was accomplished by operating three simulated landfill reactors representing the three phases of degradation, acid formation phase, methanogenic phase, and final maturation phase. As a comparison, two types of waste were used in this investigation which were reactor A (fruit and vegetable) and reactor B (Para grass). Leachate from three stages of degradation was collected and the ability to leach cadmium from contaminated soil was determined by leaching test. Moreover, this ability of leachate was compared with the ability of water (H[subscript 2]O) as control, extraction fluid#1 (TCLP), HNO[subscript 3], 0.04 M EDTA, 1 M CaCl [subscript 2] , and 0.05 M Ca(NO [subscript 3])2. For reactor A (fruit and vegetable), the Cd concentrations determined from soil samples collected from site 2 were 2.27, 3.82 and 4.32 mg/kg. For site 3, the Cd concentrations were 2.39, 4.28 and 4.98 mg/kg for the three phases respectively. However, the biological and chemical processes occurred in reactor A3 was not completly anaerobic. Reactor A3 might have to high organics in leachate and caused on incomplete attainment of the final maturation in the degradation process. In conclusion, the phases of stabilization of reactor A2 and A3 were at the initial methane formation. In contrast, the Para grass had the complete reaction and reached the final maturation phase. The leaching potential of grass leachate decreased with time. The Cd concentrations were 2.56, 1.03 and 1.35 mg/kg of Cd for soil samples collected from site 2 and 3.01, 1.44 and 1.55 mg/kg of Cd for soil samples collected from site 3 for the three phases, respectively. Leachate from grass waste had lower potential than that of fruit and vegetable waste. This indicated that leachate has an ability to leach some of non-labile fractions of Cd from soil samples. Nevertheless, the results demonstrated that the leaching ability from both leachate sources was lower than that of EDTA.