Abstract
This paper presents the results of laboratory investigation conducted to determine the variation of geotechnical properties of synthetic municipal solid waste (MSW) at different phases of degradation. Synthetic MSW samples were prepared based on the composition of MSW generated in the United States and were degraded in bioreactors with leachate recirculation. Degradation of the synthetic MSW was quantified based on the gas composition and organic content, and the samples exhumed from the bioreactor cells at different phases of degradation were tested for the geotechnical properties. Hydraulic conductivity, compressibility and shear strength of initial and degraded synthetic MSW were all determined at constant initial moisture content of 50% on wet weight basis. Hydraulic conductivity of synthetic MSW was reduced by two orders of magnitude due to degradation. Compression ratio was reduced from 0.34 for initial fresh waste to 0.15 for the mostly degraded waste. Direct shear tests showed that the fresh and degraded synthetic MSW exhibited continuous strength gain with increase in horizontal deformation, with the cohesion increased from 1 kPa for fresh MSW to 16–40 kPa for degraded MSW and the friction angle decreased from 35° for fresh MSW to 28° for degraded MSW. During the triaxial tests under CU condition, the total strength parameters, cohesion and friction angle, were found to vary from 21 to 57 kPa and 1° to 9°, respectively, while the effective strength parameters, cohesion and friction angle varied from 18 to 56 kPa and from 1° to 11°, respectively. Similar to direct shear test results, as the waste degrades an increase in cohesion and slight decrease in friction angle was observed. Decreased friction angle and increased cohesion with increased degradation is believed to be due to the highly cohesive nature of the synthetic MSW. Variation of synthetic MSW properties from this study also suggests that significant changes in geotechnical properties of MSW can occur due to enhanced degradation induced by leachate recirculation.
Highlights
Bioreactor landfill technology involves injecting leachate and other supplemental liquids into the waste to accelerate or enhance the anaerobic biodegradation of municipal solid waste (MSW)
Variation of synthetic MSW properties from this study suggests that significant changes in geotechnical properties of MSW can occur due to enhanced degradation induced by leachate recirculation
The moisture content, organic content, specific gravity, and grain size distribution of the exhumed synthetic MSW samples from the bioreactors at different phases of degradation are summarized in Table 1 and Figure 2
Summary
Bioreactor landfill technology involves injecting leachate and other supplemental liquids into the waste to accelerate or enhance the anaerobic biodegradation of MSW. Bioreactor landfills offer a sustainable way to achieve higher rates of MSW degradation, faster reduction of leachate and landfill gas pollution potential, and an increase in landfill volumetric capacity. They offer significant reductions in post-closure management as a result of the reduced period for leachate and gas generation (Sharma and Reddy, 2004; ITRC, 2006). Some of the well-designed demonstration projects showed accelerated stabilization of MSW based on the quantity and quality of landfill gas produced and the amount of landfill settlement (Reddy and Bogner, 2003; ITRC, 2006; Benson et al, 2007). Controlled leachate recirculation operations are essential to prevent built-up of pore water pressures in the landfill and prevent any failures
Sign-in/Register to view highlights & summary 
Submitted Version (
Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call