Studys On Screening Of High Effective Oil-degrading Bacteria And Enhancing Its Oil Removal Efficiency By Meganetic Field

The marine has played a very important role in the development of human society for providing the material basis for the survival and development of the people.The rapid development of shipping has impacted on the marine environment inevitably,since the twenty-first century.The oily bilge water has been one of the mobile sources of marine oil pollutions.In order to protect the marine environment,more and more stringent discharge standards were enacted by the International Maritime Organization(IMO)so that the traditional method of physical separation cannot meet the new requirement.Membrane Bio-Reactor(MBR)is a new sewage treatment technology that combine traditional biochemical process with membrane technique.As it has a compacted structure and high separation efficiency,it is very suitable for oily bilge wastewater treatment.Magnetic strengthening technology can improve the biological activity and promote the degradation of organic matters and it has became a research focus in recent years.In order to improve the biodegradation efficiency of oil,screening of petroleum degrading bacteria and magnetic fields enhanced biodegradation were studied in this paper and the property of magnetized water and the impact of magnetic fields on enzyme activity were studied to explore the mechanisms of magnetic fields enhanced biodegradation.Firstly,22 oil-degrading strains were isolated from the activated sludge of Daqing oilfield wastewater which could use the oil as the sole carbon source and the highest degradation rate of the strains,named B11,reached 53.6%in 7days.By studying the cultural characteristics,physiological and biochemical properties and 16S rDNA B11 was identified as Acinetobacter.Permanent magnet was used as the generator of static magnetic field which was added to the biodegradation process to enhance the oil removal efficiency from OmT to 60mT.The highest oil removal rate reached 66.0%which is increased 11.9%compared with that without magnetic field when the magnetic field intensity is 25mT.The magnetic field could shorten the generation time in logarithmic phase and can keep higher biomass in the stable phase in liquid culture under the same magnetic field intensity.Four factors affecting the growth of strain and the degradation ratio of oil were also investigated in this study,including pH,initial concentration of oil,salinity of medium and temperature of incubation.When the initial oil concentration at 1000mg/L,pH 6,salinity 1.5%and temperature 30? the best magnetic field enhanced biodegradation efficiency was reached.The dehydrogenase activity was enhanced when the magnetic field intensity was lower than 30mT and the highest dehydrogenase activity was reached under 25mT.The properties of culture medium were affected by the magnetic field,the conductivity is increased and the transmittance is decreased after 24 hours magnetization which will promot the growth of microorganisms after the magnetic field was removed.At last,through the analysis of GC-MS,the strain has a good effect on the degradation of C14-C26 alkanes and the removal efficiency became better with the carbon chain became longer.The degradation effect of short chain alkanes was enhanced by the magnetic field which promote the removal rates more than 80%for different alkanes of different length of carbon chain.