Analytical Solution for One-Dimensional Diffusion of Organic Pollutants in a Geomembrane-Bentonite Composite Barrier and Parametric Analyses.

ANALYTICAL solutions; POLLUTANTS; GEOMEMBRANES; BENTONITE; PARAMETRIC processes; POLYETHYLENE

Geomembrane-bentonite composite barrier is known as one of the most reliable and effective technologies for containing underground contamination. Analytical solution for one-dimensional diffusion of an organic solute in the three-layered composite barrier is presented for the case in which the barrier is keyed in aquitard. Parametric analyses were conducted to investigate the effects of partition coefficient and installation location of high-density polyethylene (HDPE) geomembrane, retardation factor, and thickness of bentonite slurry wall on the barrier performance using this analytical solution. The analysis results demonstrate that the containment performance of the composite barrier depends much on the partition coefficient of HDPE geomembrane over the target pollutant. The HDPE geomembrane exhibits an excellent resistance to the hydrophilic organics, which have a low partition coefficient. However, the hydrophobic organics, which have a high partition coefficient, can diffuse readily through the HDPE geomembrane. It is found that there is a special value of partition coefficient (i.e., ) at which a peak value was calculated for the mass flux through the composite barrier and a minimum value for the breakthrough time. The containment performance of the composite barrier can be enhanced by 10-20% by choosing an optimal installation location of HDPE geomembrane. An increase in the retardation factor of the bentonite results in a delay in the occurrence of the stable mass flux, but does not change its magnitude. An increase in the wall thickness not only delays the occurrence of the stable mass flux, but also significantly reduces its magnitude. [ABSTRACT FROM AUTHOR]

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