Study On Growth Characteristics And Demulsification Efficiency Of Bio Demulsifier Producing Bacteria

With the rapid development of manufacturing, transportation, oil extraction recently, more oil wastewater, especially the crude oil emulsion, was discharged into the environment. It was very difficult to treat and could pollute ecological environment deeply. Generally, chemical demulsifier has been widely used in treating the oil emulsion. However, it could cause the second pollution. Therefore, it becomes necessary to exploit the high efficient bio-demulsifier. It has the advantages, such as non-toxicity, non-secondary pollution, easily biodegradable and environmentally safe. The exploitation of bio-demulsifier is significant for reducing the unnecessarily environmental pollution, protecting humans health and realizing sustainable development. The major research contained isolation of bio-demulsification bacteria, growth characteristics, culture and optimization for their demulsifying conditions. Studies on effective component analysis, fermentation kinetics and demulsification mechanisms were rare.Bio-demulsification bacterium, strain XH-1 conserved in our lab with high demulsification efficiency, was identified as Bacillus mojavensis. Demulsification activity of stain XH-1 was studied. The seasonal fluctuation has been found, which could be recovered by rejuvenation. The effect of environmental factors on growth and demulsification efficiency of this strain was also investigated. The optimum culture conditions was as follows: initial pH of medium with 7, 100mL liquid volume in flask, 5% inoculation amount, and 18~20h culture time. The optimum nutrient conditions were: 10g/L glouse, 4% volume ratio of liquid paraffin, 4g/L ammonium nitrate and 1g/L yeast extract. The optimum demulsification conditions were as follows: 2mL bacterial added to 5mL model emulsion, pH values of emulsion from 5~9, and 100% demusification ratio for 48h. Ammonium sulfate slution with 75% saturation could make good results in crude extract of extracellular protein. Protein content was determined using BCA kits, and the protein content was from increase to reduction, and then from incrase to reduction again.Under the experimental data of batch culture in shake flask, bacterial growth kinetic model was constructed by Logistic equation, which obtained the good results of nonlinear fitting by Origin. From amplication culture in 5L fermentor, strain biomass was enlarged. There was no change of delayed phase and log phase, but stationary phase shorten for 6 hours. Demulsification efficicency changed little. Glucose and nitrogen were consumed sufficiently for growth. Dissolved oxygen was in low level after cultured for 6h. Finally, pH increased from 6.5 to 8~9.During the whole study, the demulsification activity of strain XH-1 was high efficient and stable, which was a kind of available bio-demulsification bacterium. It was in widely space of application, compared with chemical demulsifier. Above all, strain XH-1 had profound significance in reducing the environmental pollution. It must have a spacious developmental market in the future.