MUNICIPAL LANDFILL BIODEGRADATION AND SETTLEMENT

Landfills are frequently considered for urban development, but have li mited end uses due to large differential settlements, leachate generat ion, and gas emissions. Current landfill design with top- and bottom-l iner systems minimize entry of moisture and increase the period requir ed for stabilization of the refuse to occur. The objective of this stu dy is to test the ability of biological enhancement to reduce the time to reach biological stabilization of the waste to nondegradable matte r, and to determine the effects of biodegradation on settlement. To ac complish this, six landfill test cells were constructed to model both settlement and decomposition over extended periods. Three cells were d esigned to simulate bioreactor landfills, while another three were des igned to simulate secure vaults. Results demonstrate that secondary se ttlement is linear with the logarithm of time, and decomposition is we ll represented by a first-order model. Comparisons indicate that in th e short term there is no significant increase in the settlement rate d ue to biodegradation; however, extrapolation suggests that in the long term the settlement rate will likely increase as the effects of decom position become more significant.