Effects of humic acid on the process of microbial induced carbonate precipitation

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Biocementation research has been growing exponentially in recent years with more and more attention on sustainable techniques. Microbial Induced Carbonate Precipitation (MICP) cements soil particles by calcium carbonate formation microbially induced by urea hydrolysis. Most researches have been focusing on the stabilization of sandy soils, without considering the organic compounds that are 5% of natural soils on average. To investigate the effect of organic matter on MICP, humic substances (HS) should be taken into consideration. In general, this study attempts to figure out what is the effect of humic acid (HA), one fraction of HS, on bacterial growth and urease activity. In this study, three strains isolated from two different soils in Hokkaido were tested. With small addition (0.1, 0.5, 1.0, 1.5%) of HA added into the culture medium, the growth of three species was stimulated to varying degrees. In respect of urease activity, one strain showed an optimal performance with a 0.1% addition of HA, and the other two strains activity showed an increasing tendency with increasing addition of HA. For three tested strains, no inhibition effects were found in the aspects of growth and activity. As for the mechanism, the stimulation effects could be attributed to the more efficient utilization of energy that is necessary for bacteria reproduction. As a baseline study, it could contribute to an insightful understanding of the MICP process when applying the technique in a field rich in organic matter.

9th International Congress on Environmental Geotechnics (ICEG2023)

Biogeotechnics and Bioremediation