Effects of Bacterial Density on Growth Rate and Characteristics of Microbial-Induced CaCO3 Precipitates: Particle-Scale Experimental Study

AbstractMicrobial-induced carbonate precipitation (MICP) has been explored for more than a decade as a promising soil improvement technique. However, it is still challenging to predict and control the growth rate and characteristics of CaCO3 precipitates, which directly affect the engineering perfor...

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Bibliographic Details
Published in:Journal of geotechnical and geoenvironmental engineering 2021-06, Vol.147 (6)
Main Authors: Wang, Yuze, Soga, Kenichi, DeJong, Jason T, Kabla, Alexandre J
Format: Article
Language:English
Subjects:
Bacteria
Calcium carbonate
Carbonates
Cells
Chemical precipitation
Crystals
Density
Growth rate
Microfluidics
Microorganisms
Precipitates
Precipitation rate
Scale models
Soil
Soil improvement
Soil treatment
Technical Papers
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Summary:AbstractMicrobial-induced carbonate precipitation (MICP) has been explored for more than a decade as a promising soil improvement technique. However, it is still challenging to predict and control the growth rate and characteristics of CaCO3 precipitates, which directly affect the engineering performance of MICP-treated soils. In this study, we employ a microfluidics-based pore-scale model to observe the effect of bacterial density on the growth rate and characteristics of CaCO3 precipitates during MICP processes occurring at the sand particle scale. Results show that the precipitation rate of CaCO3 increases with bacterial density in the range between 0.6×108 and 5.2×108  cells/mL. Bacterial density also affects both the size and number of CaCO3 crystals. A low bacterial density of 0.6×108  cells/mL produced 1.1×106 crystals/mL with an average crystal volume of 8,000 μm3, whereas a high bacterial density of 5.2×108  cells/mL resulted in more crystals (2.0×107crystals/mL), but with a smaller average crystal volume of 450  μm3. The produced CaCO3 crystals were stable when the bacterial density was 0.6×108  cells/mL. When the bacterial density was 4–10 times higher, the crystals were first unstable and then transformed into more stable CaCO3 crystals. This suggests that bacterial density should be an important consideration in the design of MICP protocols.
ISSN:1090-0241
1943-5606
DOI:10.1061/(ASCE)GT.1943-5606.0002509