Study On The Treatment Of Oil Spills By Immobilized Oil-degraded Bacteria

The exploitation and utilization of offshore oil resources and the prosperity of the marine transportation industry have led to more and more oil spilling in the sea.The use of physical and chemical methods cannot eliminate oil spills completely,while biological treatment is the only way to completely and environmentally friendly eliminate oil spills.In this dissertation,oil-degraded micro-organisms were separated from the soil near the sea contaminated by oil spills.Meanwhile,the sodium alginate was used to prepare the immobilized carrier material of oil degrading bacteria.The effects of foaming agent and coating material on the performance of floating microsphere carrier material were mainly studied.Moreover,the factors which affect the performance of immobilized microorganisms and the mechanism that microorganisms degraded oils were also stated.The conclusions were listed as follows:?1?Oil-degraded micro-organisms,which were isolated from the oil-bearing soil of the marsh near Bohai Sea,were identified as Alcanivorax pacificus and Proteus Vulgaris by microscopic observation and 16S r DNA method.?2?The density and mechanical strength of the floating microspheres increased with the increase of the sodium alginate concentration.The minimum density of the floating microspheres with Ca CO₃and Na HCO₃as blowing agents was respectively0.684 g·cm^-3and 0.923 g·cm^-3,and the maximum mechanical strength was 3 N and1.2 N.?3?The optimum concentration of CACO₃as foaming agent was about 30g·L^-1,at such condition,the density of floating microsphere was 0.868 g·cm^-3,the mechanical strength 3 N,the oil retention over 83%.While the optimum concentration of Na HCO₃as foaming agent was 20 g·L^-1,the density of the floating microspheres was about 0.95 g·cm^-3,the mechanical strength as 0.7 N,and the retention of oil as 67%.It is obvious that when Ca CO₃was used as the foaming agent to prepare floating microspheres,they had more inner pores and the surface area was larger,as a result,they could load more oil-degraded micro-organisms and the oil spill removal efficiency could be increased effectively.Therefore,Ca CO₃is more suitable as the foaming agent to prepare the floating microspheres.?4?When ethyl cellulose was used to coat the floating microspheres,the density of alginate floating microspheres increased firstly,then decreased and increased again with the increase of the ethyl cellulose concentration.However,the densities of floating microspheres were always smaller than that of water as 1 g·cm^-3.Meanwhile,the maximum strength of the floating microspheres was 3.2 N,the average adsorption capacity increased with its concentration,and the average oil retention increased first and then decreased with ethyl cellulose concentration.While when chitosan was used as the coating material,the densities of the floating microspheres increased firstly and then decreased.Moreover,when the density of chitosan was more than 30 g·L^-1,the viscosity of chitosan was too large to form a microsphere.The average adsorption capacity decreased at first and then increased with the increase of chitosan concentration,and the average oil retention increased.It indicates that the performance of ethyl cellulose as coating material was more stable,the average adsorption capacity was larger,the average oil retention was larger,and the concentration range which could be selected was larger.Therefore,according to the effect of the coating material on the density of the floating microspheres,ethyl cellulose should be chosen as the coating material,and the optimum concentration of it was 40 g·L^-1.?5?With the increase of p H,temperature and inoculation amount,the degradation rate of crude oil increased firstly and then decreased.When the p H was 7,the temperature 35°C and the inoculation amount of oil-degraded micro-organisms15%,the immobilized microorganisms could degrade oil more efficiently.?6?The degradation rate of crude oil respectively by free and immobilized WX2strain increased firstly and then tended to be stable with the degradation time.Meanwhile,the degradation rate of crude oil by immobilized WX2 strain was higher than that of free strain during the same degradation time,which indicates that sodium alginate/Ethyl cellulose immobilized carrier can effectively improve the degradation rate of crude oil by WX2 strain.?7?Phenanthrene was degraded in a way of C-3,4 di-oxygenated and salicylic acid,and C-1,2 di-oxygenated metabolism might exist.In this paper,floating microsphere immobilizing oil-degraded bacteria was applied to the treatment of marine oil spills,which provided a new idea for large-scale marine oil spill treatment and provided data and theoretical support for the following researchers.The performance of immobilized microspheres in treating oil spill is expected to be greatly improved by the selection of materials and optimization of conditions.In the later stage,with the development of the production technology and conditions,the floating microspheres loaded with oil-degraded bacteria can also be used in other fields of water pollution.It is of great significance to the sustainable development of ecological environment.