Prediction of municipal solid waste landfill settlement with leachate recirculation

In case of bioreactor landfills, waste settlement will include creep and biological components due to the heterogeneous nature of waste particles, and accelerated biodegradation, respectively, as leachate is recycled. Most settlement models were not developed considering the leachate recirculation effect on settlement. The objective of this paper is to present a settlement prediction model, which accounts for changes in material characteristics as a function of the waste degradation rate. Settlement components including creep and biodegradation effects are identified as a function of the state of decomposition. The degree of decomposition was characterized through gas generation rates and the cellulose plus hemicellulose to lignin ratio. Compression indices representing creep and biological effects were measured on samples ranging from fresh to well-decomposed refuse. In addition, the time factors for the compressibility were determined from the gas production. Finally the proposed model was verified using the settlement data obtained from different landfills.