| Crude oil is one of the essential energy sources in human production and life.In recent years,oil and gas exploration,production,loading and unloading,storage and transportation and storage tank leakage causes the emission of crude oil pollutants into the marine environment,which has brought serious threats to the marine environment.Biological methods have the advantages of low environmental impact,high economic applicability,and reduced toxicity of crude oil pollutants.They are often used to remove and recover oil spills.In this study,the factors affecting the degradation of crude oil pollutants in Marine environment were analyzed.Sodium alginate-polyvinyl alcohol-citric acid modified ramie embedded crude oil degradation bacteria were used to make immobilized microspheres.Response surface was used to optimize the embedding conditions of immobilized microspheres.Degradation kinetics of free and immobilized strains was studied by using Monod equation.The degradation characteristics of crude oil degrading bacteria and the composition changes of crude oil before and after degradation were analyzed.The main research situation is as follows:(1)Based on the method of comparative analysis,the effects of pollutants,carrier materials,microbial species and immobilization methods on the degradation rate of crude oil pollution in Marine environment were studied.The results showed that the degradation efficiency of the immobilized bacteria was better than that of the free bacteria,and the carrier material had a great influence on the degradation rate,and there was no significant difference in the degradation rate between the two immobilized methods.In the future,the availability of immobilization technology should be strengthened in the actual marine environment.(2)The immobilized microspheres were made of sodium alginate-polyvinyl alcohol-citric acid modified ramie embedded with crude oil degradation bacteria.The three influencing factors of SA:PVA ratio,the addition amount of bacterial liquid and the addition amount of modified ramie were analyzed and optimized by using the response surface.When the ratio of SA:PVA was 3:2,adding 0.25 g citric acid modified ramie material and 15 m L bacterial liquid to make the immobilized microsphere,the maximum ideal degradation rate of crude oil could reach 76.13%.(3)The Fourier infrared spectrum of citric acid modified ramie fiber showed that the material has good hydrophobicity.Scanning electron microscope images showed that the internal structure of the immobilized microspheres provided enough space for the metabolic growth of microorganisms.Immobilization can make the crude oil degrading bacteria adapt to the change of external temperature and p H.When the initial concentration of crude oil is low,the degradation effect of crude oil is better.The immobilized bacteria can resist the invasion of external heavy metal ions to a certain extent.Adding nutrients to the degradation medium,the reproduction rate of microorganisms was enhanced and the degradation rate of crude oil was improved.The degradation kinetics of both the free and the immobilized strains were linear simplified in accordance with the Monod equation,and the degradation effect of the immobilized strain was much better than that of the free strain.(4)The degradation rate of immobilized bacteria was higher than that of free bacteria.The GC-MS diagram showed that the degradation effect of the immobilized bacteria was higher than that of the free bacteria.The composition of the substances before and after the degradation did not change much,and neither the free bacteria nor the immobilized bacteria could achieve complete degradation of a component.There was no significant difference in the components and degradability of aromatic hydrocarbons between the free bacteria and the immobilized bacteria.The free bacteria and the immobilized bacteria had poor degradability of aromatic hydrocarbons,and the crude oil degrading bacteria had poor utilization ability of aromatic hydrocarbons. |
PDF Full Text Request