Construction Of A Strengthened Marine Oil Snow System And Simulation Study Of Marine Oil Spill Removal By Strengthened Marine Oil Snow System

Under the action of waves and currents,marine oil spills will interact with clay particles and microorganisms in seawater to form marine oil snow（MOS）and gradually migrate to the seabed.The density of petroleum-degrading bacteria.contained in MOS is low,and its ability to degrade the entrained oil is limited.Therefore,the settled MOS will continue to release oil into the ocean,posing a threat to the marine ecosystem.Biochar（BC）has the advantages of large specific surface area and high porosity,which not only has excellent adsorption capacity,but also provides a good growth environment for microorganisms and can be used for enhanced remediation of oil pollution.In this study,different agricultural wastes were used as raw materials to prepare BC,and the effect of different pyrolysis time and pyrolysis temperature on the oil absorption capacity of BC was investigated,and 4 kinds of BC with high oil absorption performance were screened out.6strains of petroleum-degrading dominant bacteria were isolated from oil-contaminated seawater and construction of a petroleum-degrading bacterial flora.Immobilization of mixed colonies onto BC for the preparation of MOS stimulation agent,and the optimal conditions for immobilization were explored.Under the action of stimulation agent,the effects of different dispersant oil rate（DOR）,water turbulence intensity and kaolin content on MOS floc generation under the action of reinforcing agents,and determined the optimal conditions for MOS stimulation agent.Under this condition,the Strengthened-MOS（S-MOS）system was constructed,the physicochemical and biochemical properties of the S-MOS system were studied,and the mechanism of oil removal was explored.The main findings of the study are as follows:（1）24 kinds of BC were prepared under different pyrolysis time and pyrolysis temperature using pine wood,corn cob and corn stover,and their oil absorption capacity was compared.The results show that the type of raw material and the pyrolysis temperature can affect the oil absorption capacity of BC more than the pyrolysis time.Four kinds of BCs with strong oil absorption were preliminarily screened:400℃pine BC（3-400 PBC）,500℃pine BC（3-500 PBC）,400℃corn stover BC（2-400 MBC）and 500℃corn stover BC（2-500MBC）.（2）6 strains of petroleum-degrading bacteria were isolated and screened from petroleum-contaminated seawater:DG-1,DG-2,DG-3,DG-4,DG-5 and DG-6,and the degradation rates of petroleum in seawater ranged from 14.3%to 23.8%in 7 d.4 strains with high degradation rates were selected and mixed in equal proportions to build mixed flora MF,and the degradation rate of MF for petroleum in seawater increased to 35.25%,indicating that the constructed bacterial colony formed a synergistic effect among the strains,which improved the biodegradation rate of oil in seawater.（3）The MOS stimulation agent was prepared with BC from different material sources as the carrier,and the optimal immobilization conditions of the mixed bacteria were studied.The results showed that the immobilization rate of 3-500 PBC to mixed bacteria was high.When the inoculum amount was 12%,the shaking speed was 180 r/min,and the fixing time was 4 h,the immobilization rate of mixed bacteria reached 75.16%.Under the action of this stimulation agent,the removal rate of oil in seawater is as high as 67.25%.（4）The optimal conditions for the formation of MOS flocs were studied under the action of the intensifier.The results showed that:when the DOR was 1:5,the shaking speed was 160r/min,and the kaolin content was 70 mg/L,the floc formation rate was faster,and the It is dense and has a high oil capture rate for oil in seawater.（5）The S-MOS system was constructed under optimal conditions and its mechanism of oil removal was studied.The results show that compared with MOS without enhancer,the number of flocs formed in S-MOS is larger,and the size of flocs is larger（about 40μm）during the experimental period;the fractal dimension of flocs remains at 1.69,indicating that the flocs are more dense;and the floc settling rate was as low as 2.53 mm/s.（6）The EPS content of S-MOS flocs was 102.8μg/m L,which was much higher than that of MOS,and the proportion of tightly bound EPS was higher,so the number of S-MOS flocs formed was larger,larger and denser.S-MOS flocs contain more proteins and polysaccharides,indicating that the hydrophobicity of the flocs is enhanced and the adsorption sites are increased after strengthening,the flocs have a stronger ability to capture oil in seawater,and the S-MOS system has a higher oil removal rate.（7）The BC in the S-MOS system provides a relatively stable microenvironment for the degrading bacteria,thereby promoting the metabolism and reproduction of the degrading bacteria.The activities of dehydrogenase and catalase in the S-MOS system are much higher than those in the MOS system,and the degradation rate of petroleum is as high as 72.3%.The degradation process conformed to the first-order kinetic equation,the reaction kinetic constant was 0.0767d^-1,and the oil half-life was 9.03d.It shows that the addition of the stimulation agent improves the activity of the enzyme in the S-MOS system and accelerates the degradation of petroleum.