Transpiration Drying of Sanitary Landfillsa

Abstract

ABSTRACTExperiments are described which test the feasibility of diminishing the leachate production of sanitary landfills by using the roots of transpiring plants to dry the refuse and surrounding soil. Full‐scale models of landfill cores were constructed and filled with typical municipal refuse in the early spring of 1973. Selected plant species such as slash pine, thorny elaeagnus, bristly locust, black locust, and two grasses were used to vegetate two landfill models, while a third was denied vegetation and used as a control. Intermediate term results have been positive from several viewpoints. The various species of selected plants have thrived, even though gas sampling indicated that the lower two‐thirds of the landfill models quickly became anaerobic. Roots proliferated rapidly through the top 2 1/2 feet (76.2 cm.) of cover soil and first refuse layer. Following December 1973, all three lysimeters began producing leachate. However, the volume of leachate produced differed considerably depending on whether the particular lysimeter was vegetated or fallow. To date, the unvegetated control has produced 17.53 inches (44.53 cm.) while the two vegetated models have produced 8.59 inches (21.82 cm.) and 2.49 inches (6.32 cm.) respectively. The lysimeter producing the minimum leachate volume was vegetated with pine and thorny elaeagnus. The unvegetated bin produced the most dilute leachate. If one uses the chemical oxygen demand, the total Kjeldahl nitrogen, and the total solids as indices representative of the potency of leachate, then the leachate from the lysimeter containing pine and thorny elaeagnus was 1.97 times more concentrated than that from the fallow lysimeter. Thus one realizes a net improvement factor of 3.57 due to the presence of plants.