Effect of plastic fragments on hydraulic characteristics of pretreated municipal solid waste

Abstract

A systematic study was undertaken of the granular composition and hydraulic properties of municipal solid waste (MSW) produced by mechanical–biological pretreatment (MBP–MSW) from three different treatment plants with the aim of evaluating the potential application of MBP–MSW as an alternative barrier material for landfill final cover systems. Despite its coarse granular composition, MBP–MSW has low hydraulic conductivity. Long-term permeability tests show that the hydraulic conductivity decreases with time. The most likely explanation for the long-term changes in permeability is the swelling of organic material contained within the compost. In the case of saturated flow, the virtually impermeable plastic fragments embedded in the material impede fluid flow. In the unsaturated case, such fragments slow down the drying process by disrupting fluid flow and allowing pooling of water above horizontally oriented fragments. The larger the number and size of the plastic fragments, the greater the influence on hydraulic conductivity and shrinkage. These processes can be better understood with the newly developed conceptual model, the thin-sheet model. Based on this conceptual model, laboratory tests were undertaken to compare natural soil material with mixtures of soil material and plastic fragments. Corresponding numerical simulations of some experiments verified the influence of plastic fragments on the hydraulic properties of MBP–MSW.Key words: mechanical–biological pretreatment, municipal solid waste (MSW), thin-sheet model, plastic fragment, hydraulic conductivity, drying test.

Evaluation of the geotechnical properties of MSW in two Brazilian landfills

“…In the case of saturated flow, the virtually impermeable plastic fragments embedded in the material obstruct the flow of fluids. The larger the amount and size of the plastic fragments, the greater the influence on permeability (Xie et al, 2006).…”

Spectroscopic and Wet Chemical Characterization of Solid Waste Organic Matter of Different Age in Landfill Sites, Southern Germany

“…2). Moisture content still seemed to be controlled by structure and bedding of the waste at the time of deposition causing preferential flow (Huber et al, 2004; Katers and Walczak, 2005; Xie et al, 2006). It is especially indicated at Erbenschwang.…”

“…Huber et al (2004) showed that most of the waste material revealed unchanged even after more than 15 yr since deposition by inadequate wetting, and that leachate analysis will therefore underestimate long-term emission potentials. In addition, Xie et al (2006) found that the hydraulic conductivity decreases with time in MSW landfi ll bodies. More than 500 g kg −1 of waste organic matter (WOM) were present in the carbohydrate fraction, the most suited compounds for microbial decay, still providing a high potential for methane emissions and energy production at the studied sites and in landfi ll sites of similar conditions in general despite more than 25 yr of rotting.…”

“…Huber et al (2004) showed that most of the waste material revealed unchanged even after more than 15 yr since deposition by inadequate wetting, and that leachate analysis will therefore underestimate long‐term emission potentials. In addition, Xie et al (2006) found that the hydraulic conductivity decreases with time in MSW landfill bodies.…”

Investigation of the Geotechnical Properties of Municipal Solid Waste as a Function of Placement Conditions

“…Consequently, long periods of time are required to reach steady state conditions. Xie et al (2006) stated that, for a sample of similar size to that used in this test program (maximum particle size of 40 mm), the minimum time necessary to reach a steady state between inflow and outflow would be approximately 1 to 4 months. Durmusoglu et al (2006) determined that the hydraulic conductivity of wastes was not particularly sensitive to the applied hydraulic gradient.…”