Composite layers of bentonite and polyurethane (PU) foam with local sand and yellow brown soil were experimented in batch, column, and pilot-scale to simulate in-situ treatment of landfill leachate. The composite layers acted as both sorption and biodegradation barrier with control of hydraulic conductivity. In order to enhance microbial activity, oxygen and methanol were supplied through diffusion from the silicon tubings using peristaltic pump. Scanning electron microscopic analysis indicated that microorganisms were attached on the surface of PU foam. A batch test showed that PU foam was more effective in sorbing nitrate than powdered activated carbon. In the column experiment with 20% of PU foam, about 96% of BOD, 63% of COD, 74% of total nitrogen, and 83% of color were removed using the proposed layers. The COD removal rate in pilot-scale experiment was about 30%.