Study On Performance Regulation And Kinetics Of Immobilized Microflora In Degradation Of Marine Oil Spill

With the rapid development of international shipping industry,global shipping is becoming more and more frequent.Among the many methods to control oil spill pollution,biological method has become the most potential oil spill treatment method with its advantages of safety,environmental protection,and thorough restoration.However,there are several key problems in the treatment of oil spill by biological method.Firstly,the oil composition is complex,and the degradation effect of single degrading bacteria is poor and slow.Secondly,the microorganisms in nature are in a free state,degradation speed is slow,easy to lose,poor survival ability,resulting in a large loss of degradation bacteria;Moreover,microbial degradation of oil spill is a complex process,and the feasibility of using kinetic model to deal with oil spill is not supported by a large number of experimental data.In view of the above problems,this paper mainly studied the influence of bacterial community construction,carrier preparation and crude oil degradation performance.The main research contents are as follows:（1）Compound bacteria were constructed to solve the problem of poor degradation effect of oil spill.Through screening and mixing the degradation bacteria isolated from oily bilge water and oil-bearing soil,the research group obtained a group of bacteria K2with the best degradation performance and constructed its growth dynamics model.The7-day degradation rate of K2 to crude oil was 82.3%.The optimal degradation temperature 35℃,p H7～8 and salinity 2 g/L were obtained by single factor experiment.To explore the growth law of bacterial community at different p H values,salinity and temperature,the K2 modified Gompertz growth prediction model equations were established.The fitting accuracy of the established first-level model was high,with R²above 0.99.The deviation factor（B_f）and accuracy factor（A_f）obtained are between 1.0～1.1 and 1.0～1.5 respectively,indicating that the model is accurate and reliable.（2）In order to solve the problem of easy loss of microorganisms,a floating bacteria immobilized microsphere was prepared to strengthen the effective contact between bacteria and oil spill.A kind of hair-based biochar was prepared by carbonizing hair from domestic garbage and phosphoric acid modification by regulating its carbonization temperature.The thermal decomposition of hair was studied by thermogravimetric analysis,and the biochar was analyzed by FTIR,XRD,SEM and BET.It was found that it was feasible to prepare biochar from waste hair.When the carbonization temperature is 350℃,the maximum specific surface area of biochar reaches 47.7744 m²·g^-1.Then,the biocompatible sodium alginate（SA）was used as the main material,supplemented with calcium carbonate and hair-based biochar to immobilized petroleum hydrocarbon degrading bacteria.When SA concentration was 3%,the hair base biochar addition amount of 0.45%,crosslinking agent concentration was 5%,the crosslinking time of 24h,the preparation of various physical properties to achieve the optimal immobilized carrier,and to float or suspended in the water,the carrier’s internal concave and convex have send,porous,can provide protection for flora,keep the activity of bacteria.Secondly,rhamnol and natural soap powder were used to prepare a green dispersant.When the optimum agent oil ratio（DOR）is 25%,p H value is 8,temperature is 30℃and salinity is 3%,the emulsification effect is better.By measuring the surface tension of the prepared dispersant and bacteria,the synergistic effect between the two was verified.By monitoring the growth of bacteria under different compound ratio,1:9 was determined as the best compound ratio of dispersant and bacteria,and the 7-day degradation rate of crude oil after the compound ratio of dispersant and immobilized bacteria reached 92.25%.（3）Based on the experimental data obtained under optimal degradation conditions,the growth kinetics equation between crude oil concentration and immobilized bacteria was established.The kinetic equation of crude oil degradation by immobilized bacteria was as follows:lnc=-0.05398 t+9.39687.The kinetic equation model of crude oil degradation was consistent with and the kinetic equation.The correlation coefficient R²of the fitting equation was 0.97743,indicating a high degree of fitting.The half-life of crude oil degradation kinetics equation was 12.84 h,indicating that the immobilized colony K2 could react rapidly in the process of crude oil degradation and remediation.In conclusion,the immobilized bacterial agent prepared in this study shows good application potential,and the combination with dispersant can accelerate the degradation of oil spill and promote environmental remediation.