Effect of Microbial Activities on Permeability of Sand
Accumulation of microbial metabolic products namely extracellular polymeric substances (EPS), inorganic minerals and gases often clogs soil pores and reduces its permeability. Reduction in permeability of soil has both advantages and disadvantages. Changes in soil permeability, therefore, need to investigate for successful use as a bioengineering solution or to predict future problems. Permeability reduction of a soil mass can be attributed to both biogenic deposits and biogas related unsaturation. Although several studies were conducted to see the efficacy of biofilm and biomineral in reducing soil permeability, the effect of horizontally flowing growth medium, resembling groundwater in both mineral salt composition and circulation velocity, has not been studied yet. Present study mainly focuses on the influence of horizontal flow of growth media on the amount of metabolic products and saturated and unsaturated permeability of loose quartz sand (relative density of about 40%) inoculated with an aerobic microbial species Lysinibacillus sp. DRG3. In this study, microbes were instigated to produce metabolic products through three naturally occurring bioprocesses namely, non-ureolytic calcifying process, ureolytic calcifying process and non-calcifying process. Sand samples with fluvial activities yielded higher amount of biogenic precipitates, unsaturation and permeability reduction. Calcifying process resulted in lesser development of unsaturation than that for non-calcifying process probably because of higher utilization of evolved CO2 for biocalcification. Unsaturated permeability was generally lesser than the saturated one. After treatment, the unsaturated permeability decreased up to 16% of the original permeability, while the saturated permeability recorded was up to 41% of original permeability.
KeywordsPermeability Lysinibacillus sp. DRG3 Unsaturation
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