Effect of Biofilm Treatment Strategy on the Permeability Reduction of Sands

Soil improvement methods applied to reduce permeability of soils are associated with high application cost and produce large carbon footprints. Biofilm-induced permeability reduction is a bio-mediated soil improvement method that can reduce permeability up to two or more orders of magnitude. This study investigates the application of two different treatment strategies, pumped flow with a constant flow rate and gravity flow with a maximum hydraulic gradient of i=2.5, to induce biofilm formation and reduce permeability in two sizes of silica sand. The pumped flow treated columns reduced permeability at a steady rate compared to the gravity flow columns which demonstrated more variability in permeability reduction through treatment. Additionally, the biofilm formation in the pumped flow columns was more resistant to changes in hydraulic pressure.