Compressibility Parameters of Municipal Solid Waste with Leachate Recirculation

摘要

The operation of landfills with leachate recycle (bioreactors) enhances refuse decomposition and offers a number of advantages including leachate treatment and disposal as well as recovery and reuse of landfill airspace. However, settlement models have not been applied and tested in these situations. Work in this paper utilize measured data from leachate recycle test cell A, at the Mountain View controlled landfill Project, and results from laboratory oedometer testing to illustrate the feasibility of predicting waste compressibility in bioreactor landfills. The merits of the proposed method are the identification of the degradation phase, and the application of the proper compressibility parameters corresponding to the dominating mechanics of settlement (mechanistic, creep, or biological). Measured parameters from the laboratory tests on samples at Phase 1 stage of decomposition indicated creep index (C_(α1)) of 0.03 and biological degradation index (C_β1)) of 0.05. This value is approximately the sameC_(α2) of 0.03 for Phase 2 sample. As decomposition is accelerated over a period of 13 days, the sample degraded into Phase 3 and C_(β3) was estimated to be 0.19. Using these parameters and onset time of accelerated gas production to be 500 days, the measured settlement strain in the field is closely estimated. Beyond applicability of the method illustrated here to field test data, challenges arise in application to prototype landfills. These include the definition of compressibility properties of each waste sub-layer as a function of decomposition stage and moisture content as time progresses throughout the operation and post closure periods and until waste stability is reached.