American Society of Civil Engineers

Hydraulic Conductivity of Compacted Soil Treated with Biofilm

by Michael L. Dennis, A.M.ASCE, (Engr., Shephard-Wesnitzer, Flagstaff, AZ 86004) and John P. Turner, M.ASCE, (Prof., Dept. of Civ. and Arch. Engrg., Univ. of Wyoming, P.O. Box 3295, Laramie, WY 82071)

Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No. 2, February 1998, pp. 120-127, (doi:

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Document type: Journal Paper
Abstract: A laboratory study was conducted to evaluate the feasibility of creating low-permeability waste containment barriers using soil treated with bacteria to produce a plugging biofilm. The effects of exopolysaccharide-producing bacteria on the hydraulic conductivity (k) of a compacted silty sand were determined. Values of k for this soil without bacterial treatment ranged from 10–5 to 10–6 cm/s, depending on molding moisture content. Soil specimens were molded with a bacterial and nutrient solution, compacted at optimum moisture content, permeated with nutrient solutions, and tested for k using a flexible-wall permeameter. Significant reductions in k were observed, and most specimens reached a stable final k of 10–8 cm/s. The durability of the biofilm was tested by permeation with saline, acidic, and basic solutions, and by subjecting specimens to wet-dry conditions. In most cases these chemical and physical challenges had little or no effect on the reduced k. Results of these tests demonstrate that biofilm treatment may be a feasible technology for creating waste containment barriers in soil.

ASCE Subject Headings:
Biological processes
Compacted soils
Hydraulic conductivity
Waste storage