Abstract
This paper presents a technique of reducing permeability through sand using a biologically inspired process. The effect of Enzyme-Induced Carbonate Precipitation (EICP) and biopolymer (sodium alginate and guar gum) on the permeability of silica sand was investigated. The effect of the number of EICP treatment cycles and seawater on the permeability of the EICP-treated sand was evaluated in this study. Besides, the effect of varying the concentration of biopolymer on the permeability was investigated. The biopolymer concentration used in the study was 0.1, 0.3, 0.5 and 1% by dry weight of sand. The result showed that the coefficient of permeability decreased with an increase in the number of EICP treatment cycles. The precipitated calcium carbonate (CaCO
3
) within the soil pore space was observed to yield a reduction of 61% in soil permeability compared to the untreated specimens. Further increase in the number of treatment cycles yielded a higher reduction in the coefficient of permeability. Conduction of the permeability test with seawater on the EICP specimens resulted in a lower coefficient of permeability compared to those using water. Furthermore, integrating biopolymers within the soil media was capable of plugging the pores as a result of the viscous gel-forming characteristics in the presence of water. Increasing the biopolymer concentration from 0 to 1% resulted in a reduction in the coefficient of permeability by around 20-folds and 3-folds for sodium alginate and guar gum, respectively. However, a lower biopolymer concentration of 0.1% is sufficient to effect a reduction in the permeability of the silica sand by around 68% and 43% for sodium alginate and guar gum, respectively. The sodium alginate biopolymer proved more efficient in reducing the permeability of the silica sand than EICP or the guar gum biopolymer.