Time- and stress-dependent model for predicting moisture retention capacity of high-food-waste-content municipal solid waste: based on experimental evidence

Abstract

Moisture retention capacity (MRC) is a key parameter for the prediction of leachate production of a municipal solid waste (MSW) pile. In this paper, five sets of laboratory tests were conducted in compression cells to characterize the variation of MRC with degradation time and overburden stress. Set A was conducted on the fresh high-food-waste-content (HFWC)-MSW under different degradation conditions and a sustained stress; Set B was on the fresh HFWC-MSW by alternation of degradation time and incremental stresses; Sets C, D, and E were on fresh HFWC-MSW, zero-food-waste-content (NFWC)-MSW, and decomposed MSW, respectively, being subjected to incremental stresses. The following findings were obtained from the test results: (1) The MRC of fresh HFWC-MSW decreased exponentially with degradation time under a sustained stress. The higher waste temperature or oxygen introduction would result in a faster declining of MRC. (2) The MRCs decreased linearly with a logarithmic increase of stress for all the MSW samples with different food waste contents. The MRC of HFWC-MSW was higher than that of NFWC-MSW under a given stress, and the decomposed MSW took the second place. (3) The variation of MRC appeared to be independent of stress path in terms of stress and degradation time. Based on the test results, the dependencies of the MRC of HFWC-MSW on degradation and stress were interpreted. Then, a time- and stress-dependent model was proposed for predicting the MRC of HFWC-MSW. The model was relatively simple and convenient for design purposes, and was verified by the measured data of leachate production at the pretreatment container of Laogang Incineration Plant. Finally, the model was developed to evaluate the dewatering effect of the HFWC-MSW pile. The strategy of combining the degradationenhancing measures with stress-increasing measures is recommended in a rapid dewatering project.