Effect of intracellular water release on hydro-mechanical behaviors of high kitchen waste content municipal solid waste

The release of intracellular water during degradation process contributes to the great leachate production and settlement of landfilled high kitchen waste content MSW (HKWC-MSW). An oven-drying and absorbent-paper combined method was proposed to measure the intracellular and interparticle water contents of HKWC-MSW. Two degradation experiments were carried out to study the release process of intracellular water and its effect on the hydro-mechanical behaviors of HKWC-MSW. It was found that the two degradation experiments showed similar degradation behaviors with BOD/COD decreasing with time in the early stage. In the first degradation experiment, most intracellular water was released during the first two months, and the degradation of degradable matter in kitchen waste (KW) was much slower than the release process of intracellular water. The particle size became smaller and the overall grain specific gravity increased during the fast release process of intracellular water. In the second degradation experiment, after two-year degradation, the total leachate production was about 45.2% of the initial wet weight of HKWC-MSW specimen. Water retention capacity θf increased from 0.23 to 0.58 during 1–69 d, which might be caused by the decrease of particle size and compression of waste skeleton. As almost all the intracellular water was released after 80-day degradation, during the latter stage of leachate drainage under gravity, θf decreased and was close to the total volumetric water content. The total compression strain was about 0.39. The secondary compression strain during 1–80 d (i.e., about 0.07) was considered to be mainly resulted by the release of intracellular water and the subsequent drainage of leachate, and it accounted for about 22.6% of the total secondary compression strain.