Upscaling Bacterial Inoculation for Field-Scale Applications of Microbially Induced Carbonate Precipitation

AbstractMicrobially induced carbonate precipitation (MICP) has been shown to improve geotechnical properties of soil in many laboratory-scale tests. Field deployment of this technology requires large volumes of suspended bacterial inoculum media, and geotechnical engineers are still seeking a low-cost and quick method for upscaling applications. In this paper, we propose a four-step inoculation method to culture Sporoscarcina pasteurii for implementation of MICP in a prototypical dune in the Large Wave Flume at the O.H. Hinsdale Wave Research Laboratory of Oregon State University. The four-step inoculation method nonsterilely cultured the bacteria to 42 L in a common microbiology lab and scaled it up to 73 L in the field. The values of optical density at a wavelength of 600 nm (OD600) were obtained to determine the specific growth rate. Two different types of agar plates were evaluated for contamination and cell counting of the bacterial solutions. Shear-wave velocity of the treated dune was continuously measured by pairs of bender elements to monitor the treatment process. The average specific growth rates of the 42- and 73-L bacterial solutions were 5.11×10−3 and 1.27×10−3 min−1, which were quite high compared with previous studies. The plate results indicated that the four-step inoculation method provided 108 cells/mL of bacterial solution with unobserved contamination. The increase in shear-wave velocity suggested the development of biocementation within sand particle contacts of the dune, demonstrating the effectiveness of the inoculation method. The results suggest that the four-step inoculation process discussed in this paper provides a large amount of bacterial solution for field-scale application of MICP.