Philippine News Item

Effects of Bacterial Density on Growth Rate and Characteristics of Microbial-Induced CaCO3 Precipitates: Particle-Scale Experimental Study | Journal of Geotechnical and Geoenvironmental Engineering


Abstract

Microbial-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.



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