Effect Of Enhanced Biodegradation On Settlement Of Municipal Solid Waste Landfills

Recent studies of municipal solid waste landfills have revealed the influence of biodegradation upon secondary settlement. Modern landfills, however, are designed with efficient containment systems which minimise moisture ingress and thereby reduce leachate and gas generation. The shortage of moisture means that these containment systems delay decomposition and stabilisation of waste. An alternative approach is to enhance biodegradation by designing and operating landfills as bioreactors. Leachate and gas are then produced during the early stages when the containment system is new and risk of failure is low. Additionally, accelerated stabilisation allows earlier re-use of the site. This paper describes an investigation conducted in a full-scale bioreactor cell at the Lyndhurst Landfill in Victoria, Australia, to demonstrate the effect of enhanced biodegradation upon secondary settlement. A hyperbolic settlement model is used to quantify the acceleration of settlement due to enhanced biodegradation and to predict the continuing settlement-time relationship.