The basicity, water solubility, intrinsic viscosity and molecular weight of carboxymethyl chitosan (CM-chitosan) were investigated. The solution pH remained at about 9.2 at the concentration of higher than 2.0 g/L. The isoelectric point of CM-chitosan was about 4.5 of pH, and the solubility of CM-chitosan at the solution pH of 2.0 to 6.0 was lower than 5 g/L. The acetic acid could be replaced by hydrochloric acid as solvent for the viscosity-average molecular weight determination of chitosan. The intrinsic viscosity values of CM-chitosan have significant differences in acidic and alkaline conditions. The viscosity-average molecular weight of CM-chitosan was (3.8 ± 0.2) × 105, consistent with that of product chitosan of blank test.

The growth conditions of a Geobacillus sp. were investigated by single-factor experiments. The strain was strictly aerobic bacterium, and could grow on hydrocarbons as the sole carbon source. The optimum carbon and nitrogen sources were 3.0% sucrose and 0.20% KNO3, respectively. The range of temperature, salinity and pH for the bacterial growth was 35-70 °C, 0-10% NaCl and 5.5-9.5, and good growth was obtained at 35-65 °C, 0.5-8% NaCl and 6.0-9.0, respectively. Particularly, the optimum temperature for the bacterial growth was between 50 °C and 60 °C. The strain had wide adaptability to the extreme conditions, and may be potentially applied to microbial enhanced oil recovery and oil-waste bioremediation technology.

The enhanced oil recovery characteristics of a Geobacillus sp. was investigated by shake flask experiments, blind-tube oil displacement experiments and core flooding tests. The strain exhibited good properties such as resisting high temperature, taking different types of crude oil as the sole carbon source, reducing the viscosity of crude oil, emulsifying and dispersing crude oil or liquid wax. The oil in the dead area could be effectively driven out by the strain, and the oil recovery of original oil in place had been increased by 12.9-15.9% after 5 treatments in 50 days by adopting air-assistant technique (air/liquid 10:1, v/v) due to the synergistic effect of the bacteria and their metabolites such as biogas and biosurfactants. The strain seems to be a promising candidate for microbial enhanced oil recovery and underground sewage treatment technology.

The effects of the bacterial cell size and flow velocity on the transport of concentrated suspensions of bacteria were experimentally investigated, and the bacteria retention mechanism was studied by observing bacterial distribution in natural cores. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the core flooding with the smaller cell size bacteria or at a higher flow velocity. The bacteria were easier to migrate through the porous rock directionally compared to the rigid solid particles owing to their organic flexibility. Bacteria retention occurred primarily at the inlet section of the natural core, and log-jam effect or pore bridging may be the dominant mechanism.

The effects of temperature, permeability and the presence of a residual oil phase on the transport of the bacterium Geobacillus sp. were investigated experimentally in sandpack cores. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the higher permeability sandpacks, or at a higher temperature. The bacterial transport could be enhanced by the pulse injection, but reduced with the presence of residual oil. When the injected cell concentration is relatively high (>108 cells/mL), log-jam effect or pore bridging may be the primary mechanism, and the surface adhesion may act as the secondary mechanism of bacteria retention and permeability reduction.