Study On Bacterial Degrading Crude Oil With Carrier And Surfactant

With the development of the oil industry, oil-contaminated soil problems getting worse. Microbial bioremediation was considered to have broad application prospects because of simple, low-cost and no secondary pollution. But this method has the conspicuous shortcomings of two respects: lower biodegradation speed and long processing time. While the solubility of oil can increase by using surfactant. Therefore, the transfer rate of pollution will increase. It can also enhance the oil degradation and removal rate. In order to enlarge production and transportation, the microorganisms agent should be treated by immobilization. Therefore, It is very necessary to study how to immobilize microorganism select suitable surfactant.Three kinds of superiority bacterium species H1,H2,H3 which being had higher degradation effect to crude oil of Liaohe oilfield were screened from oil contaminated soil. In this study, the highest degradation rate bacterium H1 in fluid-phase decomposition experiments was choosed as the tested object. Select different carriers to immobilize microorganism by physical adsorption method, Sawdust was determined as the best adsorption carrier. The toxicity of chemical surfactant SDS, Tween80,β-CD and biosurfactant rhamnolipid at different concentrations were determined on the basis of the growth curves of microorganism H1. The growth models were also constructed according to the growth curves. When the concentration of SDS higher than 40mg/L, it shows toxicity to bacterium H1.The degradation effect of bacterium H1 on surfactants and the influence of different surfactants to solubilization of crude oil were studied. The result shows that all surfactants can be degradated by bacterium H1. Rhamnolipid biosurfactant has obvious solubilization to crude oil with the concentration of this biosurfactant increased, the solubility of crude oil also increased. Chemical surfactant SDS and Tween80 also have some solubilization effect. However,β-CD has almost no effect on the solubilization. The representative soil which typically distributes in Tianjin Binhai District, slurry silt clay, were choosed as the tested object. Under the condition of different concentration, Effect of different of surfactants on the crude oil degradation rate in this soil was studied. The experimental results indicate that chemical surfactant SDS, Tween80 andβ-CD have almost no effect to the degradation rate. But the rhamnolipid biosurfactant can promote the degradation of crude oil in soil markedly.With increasing rhamnolipid concentration, the degradation rate of oil speeded up and the degradation half life shortened. Using the double exponential model to fit the degradation of crude oil, the kinetic equation can describe the trend of crude oil degradation commendably.