Estimation of Vertical Barrier Performance Based on Microbial Improvement

Abstract

AbstractSanitary landfilling is nowadays the most common way to eliminate municipal solid wastes. However, the durability of landfill is mainly determined by the anti-seepage property of vertical cutoff walls. As microorganism has proved effective in plugging micro-pores, and greatly enhance the barrier performance of cutoff wall for MSW landfills. In this study, Escherichia coli. was selected for preconditioning towards compacted soil specimens and the hydraulic behaviours of the specimens were evaluated. According to the results, the huge amounts of microbial exopolysaccharides produced by Escherichia coli. encountered in the soil pores and formed a pore plugging, eventually caused 81–95% decrease in the hydraulic conductivity, from the initial value 5.3 × 10−5–5.6 × 10−6 cm/s to the stable value 3.1 × 10−6–2.9 × 10−7 cm/s (dropped by 1–2 orders of magnitude). The introduction of clay leads to the increase of surface roughness inside the internal pores as well as the diminution of shear forces, resulted in more effective adhesion between microorganism colonization and the surface of the particles. Subsequently, an extensive parametric analysis was conducted by numerical simulation to investigate the transport behaviour of contaminant through vertical cutoff walls. Several decrease of orders of magnitude in the hydraulic conductivity from 1 × 10−8 to 1 × 10−10 m/s resulted in the dramatical increase of the breakthrough time by 431.2% which revealed that a low hydraulic conductivity was of significance for vertical cutoff walls to achieve desirable barrier performance.KeywordsLandfillCutoff wallBarrier performanceHydraulic conductivityContaminant transportBioclogging