Biocementation and bioclogging of sand using improved MICP techniques

Abstract

from the Environmental Laboratory for rendering the help on equipment, chemicals, and laboratory testing. I am also grateful to the assistance received from my groupmates Wang Lei, Ye Dawei, and Chen Hao. In addition, I am thankful to my other colleagues, Zhang Dong, and Ruan Shaoqin for their technical support and sharing their experience in laboratory work.Last but not least, I am indebted to my parents for their unceasing support and encouragement. This Ph. D thesis is the outcome of their sacrifice.vi

Research on the Effect of Natural Seawater in Domesticating Bacillus pasteurii and Reinforcing Calcareous Sand

“…The reason for this may be that the medium used for the activation and passaging of the bacteria was de-ionised water, which the Bacillus pasteurii had already adapted to, while the seawater environment is more complicated than the de-ionised water environment, such that the bacteria had to adapt to the environment after entering it, leading to a delay period. 3 ⃝ The overall trend of bacterial liquid concentration was stable after 24 h of incubation. When the seawater gradient domestication tended to be stable, the concentration of the bacterial sap showed a gradual increase with an increase in the domestication gradient; that is, b < c-2 < d-3.…”

“…Comparing different seawater gradients, it was found that, the higher the seawater concentration, the greater the effect on the activity of the bacteria; and, the use of multiple gradients of seawater concentration to domesticate and cultivate Bacillus pasteurii better enabled the bacteria to transition from the de-ionised water environment to the seawater environment, which thus better protected the bacterial urease activity. 3 ⃝ The bacterial urease activity at the end of the multi-gradient culture test with natural seawater under different domestication schemes also slightly differed: when the bacterial concentration tended to be stable, the bacterial urease activity of b was lower than that of c-2 and d-3, while c-2 and d-3 presented alternating urease activities due to the inconsistency in the time period that they arrived at their peaks. The bacterial urease activity did not differ much in general.…”

“…In recent years, various countries have constructed a large number of artificial islands and reefs, as well as a series of defence and civil facilities in the relevant waters. Calcareous sand is a locally sourced building material used in the construction of island and reef projects in the South China Sea [1][2][3][4][5]. Calcareous sand is mainly deposited from the remains of marine organisms, such as coral and shells, and is mainly composed of calcium carbonate.…”