Weian Lin

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Preliminary findings from a large-scale experiment

A large-scale bioreactor experiment lasting for 2years was presented in this paper to investigate the biochemical, hydrological and mechanical behaviors of high food waste content (HFWC) MSW. The experimental cell was 5m in length, 5m in width and 7.5m in depth, filled with unprocessed HFWC-MSWs of 91.3 tons. In the experiment, a surcharge loading of 33.4kPa was applied on waste surface, mature leachate refilling and warm leachate recirculation were performed to improve the degradation process. In this paper, the measurements of leachate quantity, leachate level, leachate biochemistry, gas composition, waste temperature, earth pressure and waste settlement were presented, and the following observations were made: (1) 26.8m3 leachate collected from the 91.3 tons HFWC-MSW within the first two months, being 96% of the total amount collected in one year. (2) The leachate level was 88% of the waste thickness after waste filling in a close system, and reached to over 100% after a surcharge loading of 33.4kPa. (3) The self-weight effective stress of waste was observed to be close to zero under the condition of high leachate mound. Leachate drawdown led to a gain of self-weight effective stress. (4) A rapid development of waste settlement took place within the first two months, with compression strains of 0.38-0.47, being over 95% of the strain recorded in one year. The compression strain tended to increase linearly with an increase of leachate draining rate during that two months.

The Effects of Temperature on Hydraulic Conductivity of Remolded Sewage Sludge

This paper examines the effect of temperature, with the range of 20 to 70 °C, on the hydraulic conductivities of remolded sewage sludge from different regions compared with the kaolin and clay. And the hydraulic conductivities of the heated sludge were measured with the confining stress of 60,100 and 200 kPa. The measured values of hydraulic conductivities for all the sludge increase with increasing temperature, and the hydraulic conductivities at 70 °C increase up to about 25–60 times those at 20 °C, while kaolin and clay are 2–4 times. When cooling from 70 °C to 20 °C, the hydraulic conductivities of sludge were about 7 times the initial values at 20 °C, revealing a hysteresis phenomenon. The changes in viscosity of water, the amount of bound water and organic matter contents with increasing temperature contribute greatly to the significant increase of hydraulic conductivity of sludge. The study also showed the hydraulic conductivities of sludge did not decrease with increasing confining stress.

Geotechnical Engineering Properties of Solidified Sludge in Qizishan Landfill Site, China

In order to have a better understanding of solidified sludge in a sewage sludge disposal pit, field and laboratory investigation were conducted on the geotechnical properties of the solidified sludge at the Qizishan Landfill in Suzhou, China. The field investigation included borehole sampling. The laboratory test involved the measurements of water content, organic matter content and shear strength for the borehole samples taken from Qizishan landfill sludge pit. The tests results demonstrated that the cohesive intercept (c) of the solidified sludge mostly range from 15 to 60 kPa; friction angle (φ) mostly range from 6° to 40°. The unconfined compressive strength for sludge normally about 180 kPa, but the unconfined compressive strength for some cement-like samples up to 250–300 kPa. Above analysis are useful for the in-situ sludge reinforcement methods, such as first in-situ vacuum preloading combined with subsequent solidification treatment. And it can provide the necessary geotechnical parameter and partly basis for sludge disposal design.