Performance evaluations of landfill cover systems with sludge barriers

The effects of final and daily cover systems with sludge barriers on reducing quantity of rainwater percolating the cover systems, under Japanese climatic conditions, are evaluated using a water balance analysis. The leachate reduction by the installation of daily and final cover systems are predicted. The feasibility of paper sludge (PS), construction sludge (CS), and bentonite mixed construction sludge (CSB) as barrier layers is experimentally evaluated in order to investigate the effectiveness of sludge barriers. A parametric water balance analysis indicates that a rainwater interception rate of more than 95% can be achieved through the use of final cover systems, to which sludge barriers with a layer thickness of more than 100 mm and a hydraulic conductivity of 1 × 10-7 cm/s are applied. When sludge barrier layers have hydraulic conductivity of less than 1 × 10-5 cm/s, daily cover systems exhibit a satisfactory performance of rainwater interception. The quantity of leachate generated in a waste layer, through the installation of a final cover system, decreased to 1.7% in comparison to systems having only a surface layer. The experimental results indicate that compacted PS, CS, and CSB can exhibit low levels of hydraulic conductivity and environmentally acceptable level of heavy metals, so that they may be applied as the barrier layer for the cover systems.