Microbially induced calcite precipitation in calcareous soils by endogenous Bacillus cereus, at high pH and harsh weather.

Microbially induced calcite precipitation (MICP) improves the physical properties of soils by increasing the solid content, decreasing the pore sizes and improving the rigidity of the particle-to-particle contact ending with a better mechanical and geotechnical performances of the soils. First, the physical characteristics of soils in Qatar showed similar grain size distributions with most falling in the category of fine particles (30 μm-1 μm), which is appropriate for MICP processes. MICP is ensured by the ureolytic activity of urease producing bacteria. However, Qatari soils are characterized with high carbonate contents exceeding 20%, high alkalinity and fluctuations of temperature and aeration. Although such properties can cause calcite dissolution as reported in literature, two Qatari endogenous B. cereus strains, QBB4 and QBB5, were shown able to adapt to the harsh conditions and induce mineral formations by MICP. Their optimal potentials was at wide ranges of temperature from 30 °C to 42 °C and pH from 7.0 to 8.0. Using Qatari bacteria in liquid cultures and at syringe level at laboratory conditions, as well as in plots at field conditions, 16% CaCO

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