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Applied Basic Study on the Bioremediation Technology in Oil-contaminated Marine Shorelines

Author: WangLiNa
Tutor: BaoMuTai
School: Ocean University of China
Course: Marine Chemical Engineering and Technology
Keywords: marine oil spill crude oil biodegradation bioremediation
CLC: X55
Type: PhD thesis
Year: 2013
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Abstract


Hydrocarbon degrading bacteria are usually screened from oil-contaminatedareas. Generally, they could performe very well in laboratory oil degradingexperiments. But the bacteria usually could not reproduce their efficienthydrocarbon-degrading ability in the field environment due to the lack of the ability toadapt to the on-site envirnment. The study abroad has reached high levels onmicrobial remediation treatment technology while the techonology is still in thelaboratory research stage at home. There are few large-scale field experiments to carryout, even less stringent standards to follow. Experiments were performed to assess theeffect of environmental factors on the viability of oil-degradation bacteria in sea water.The aim is mainly to evaluate the application feasibility and screen the most suitablehydrocarbon-degrading bacteria in a proper way. All the conclusions are as follows:(1) Four hydrocarbon degrading bacteria were isolated from Qingdao Port:Ochrobactrum sp. N1(No.HQ231209), Brevibacillus parabrevis N2(No.HQ231210),Brevibacillus parabrevis N3(No.HQ231211), Brevibacillus parabrevis N4(No.HQ231212). N series bacteria combined with a biosurfactant producer Bbai-1 hashigh efficient in petroleum degrading experiment. The mixed bacteria flora couldreach into the growth stationary phase after16hours culture in the enrichmentmedium. In the oil medium, the bacteria reach into the stationary phase after20hoursculture. Cell concentration was9.12×109cell·mL-1. The optimum conditons forcrude oil degradation are determined to be pH of8.0, temperature of25oC and salinityof (NaCl%)25g·L-1.(2) The initial stage of quality loss in crude oil weathering process mainlycomes from volatilization of light component. Large molecular weight and structureof the complex hydrocarbon component of oil is rearely affected by weathering.Through gas chromatography analysis of crude oil in the weathering process, lossmainly comes from the hydrocarbon component volatilization before C17. When the oil spills are treated with chemical dispersants, the oil concentration inseawater decrease along with the increasing of water depth. When micribial agents isapplied in the treatment of oil spills, the bacteria in the initial stage only use thedissoluted oil in seawater. After the bacteria adapt to the marine environment,biosurfactant produced in the growth process could increase the dissolution of the oilcomponent. Hydrocarbon concentration in the surface of the seawater is higher thanthe one in the bottom.In the oil migration shake flask experiment, the oil-sand mixture reach theadsorption-desorption equilibrium after10hours of washing action of the sea water.The components of petroleum hydrocarbons in water is of6.40mg·L-1. Columnarsimulation experiment show that the treatment of inshore oil contaminated areasshould be strengthened within10cm of sea sand.(3) N series bacteria could degrade63.2%of the crude oil in the shake flaskexperiment. Microbial degradation of crude oil consists with first-order kinetics.Biosurfactant producer strain Bbai-1could accelerate the degradation of crude oil byN series bacteria. The degradation rate is66%.(4) The indoor mesocosm experiment is the amplification of the shake flaskexperiment. When the temperature is20oC, TVC and the number of the HDB remainat the level of107CFU·mL-1. The dissolved hydrocarbons concentration is of5.11mg·L-1. When the temperature is25oC, the room temperature is19oC. TVC and thenumber of the HDB could reach up to108CFU mL-1from107CFU mL-1. Oilconcentration in seawater is32.597to34.366mg L-1. The emulsification efficience isbetter than the one in the temperature of20oC. Based on the GC and GC-MS analysis,the degradation rate is51.1%in the temperature of25oC.(5) The field simulation experiment is conducted for103days. N series bacteriaagent is fermented a total of six tons. Biosurfactant producer strain Bbai-1isfermented to be4tons. In the experimental pool, TVC and the number of HDB areexperienced a process of decreas, increas and finally decrease. TVC in eachexperimental pool maintain at the level of106107CFU·mL-1. The number of HDB ismaintained at more than105CFU·mL-1. TVC and HDB in the control were 104CFU·mL-1and103CFU·mL-1respectively. The strains in M06(oil, the microbesare growing well in the N1-N4) and M01(oil, N1-N4, Bbai-1nutrient) grow betterthan other pools.The glycolipid content produced by the strains maintains increase ineach experimental pool. Glycolipid in M01has the hightest yield. Based on the GCand GC-MS analysis, the metabolites are mainly hexadecanoic acid and behenic acid.Molecular Ecology’s analysis shows that, with the growth of the culture time,brightness and abundance of the inocula experiment pool bands increasedsignificantly. The degradation rate in M01pool was57.39%. The average degradationrates in M06, M07and M08are39.88%,30.50%,31.99%due to the lack of nutrientsor surfactant.(6)In the bioremediation of shore site experiment, the use of zeolite adsorbinghydrocarbon degrading bacteria could tolerate the washing effect from seawater. Itcan keep the number of function bacteria in a high level. TVC and the number of theHDB in T04region are5.51×107CFU·mL-1and1.49×106CFU·mL-1respectively.TVC and the number of the HDB in T03region are3.08×106CFU·mL-1and5.90×105CFU·mL-1respectively.(7) In the bioremediation of marine sediment experiment, TVC both in thesurface water and in the bottom increase to a certaine extent compared with thecontrol station. The number of HDB in the bottom water is higher than the one in thesurface wate. The bacteria in drifting station are more than the fixed station.Glycolipid produed in the drifting stations HD06Wb and HD07Wb are43.54mg·L-1and42.98mg·L-1respectively after33days experiment. It is correspondingwith the bacteria growth trend. Molecular ecology analysis results show that theabundance and brightness on the14d and the35d are greater than the background.Each technological parameter is optimized through the series of bioremediationexperiment from indoor shake flask experiment to marine site application. Theprogram conducted in this study is the exploration, in China, in forming a commonmethod to evaluate petroleum-utilizing abilities of bioremediation agents.

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CLC: > Environmental science, safety science > Environmental pollution and its prevention > Marine pollution and its prevention
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