Formation And Characteristics Of Oil-mineral Particle Aggregates Under The Action Of Bacteria And Microalgae

With the increase in demand for global petroleum products and the increase in the volume of marine oil transportation,marine oil spills occur frequently.Oil spills can interact with mineral particles in the ocean to form oil-mineral aggregates OMA(Oil–Mineral Aggregation)and settle,which in turn affects the environmental behavior of the spill.In the past studies,the effects of different physical and chemical factors on OMA were mainly investigated,and the formation and characteristics of OMA under microbial action were less studied.In this paper,the formation and characteristics of OMA under the action of bacteria,microalgae and algae were studied by simulation experiments.The bacteria and microalgae were discussed by comparing the similarities and differences of bacterial community structure between OMA and water in the interaction of bacteria and algae.The role in the formation of OMA.The main conclusions are as follows:(1)Compared with the aseptic conditions,the OMA formation rate increased after the addition of the bacterial suspension,shortened from 12 hours to 7 hours;the floc size became larger,the maximum size of OMA under the action of bacteria was cm,and?m under sterile conditions.Under sterile conditions,the morphology of OMA is mostly oil droplets,and the morphology of OMA under the action of bacteria can be:filamentous,fibrous,reticular and globular.(2)Under the action of bacteria,as the amount of bacterial suspension increased,the formation rate of OMA formed increased.The content of petroleum hydrocarbons in the aqueous phase gradually decreased from 149 mg/L to 120 mg/L,and the oil recovery per unit floc increased from 0.40 mg/mg to 0.43mg/mg;the amount of TEP was also increased,and the area increased from 3.4×10~8?m~2 to 4.0×10~8?m~2.(3)High-throughput sequencing results showed that under the action of bacteria,the richness and diversity of bacteria in OMA were larger than those in water.A total of235 OTUs were observed in OMA and water,of which 70.64%were shared by both.At the genus level,the dominant genus in OMA is Maricaulis,Alcanivorax,Vibrio,and the dominant genus in water is Vibrio,Alcanivorax,Thalassospira.The relatively abundant abundance of common bacterial species is Alcanivorax and Vibrio,two strains.Genus plays an important role in promoting the formation of OMA.(4)Compared with the action of bacteria,the formation rate of OMA under the action of P.sinensis is faster and can be formed in 3 hours.The largest size of OMA in algae contains endophytic bacteria up to cm level;the largest size of OMA formed after removal of endophytic bacteria is mm.Compared with the sterilized Algae,the sedimentation rate of OMA was higher in endophytes,and the maximum sedimentation rate was 6.13 mm/s on the 12th day;the petroleum hydrocarbon content in the aqueous phase was reduced from 273 mg/L to 252 mg/L;The oil capture amount of the sedimentation OMA was increased from 0.45 mg/mg to 0.55 mg/mg;the amount of TEP production was increased from 2.4×10~8?m~2 to 5.0×10~8?m~2.(5)Under the action of bacteria and microalgae,OMA has a shorter formation time and can be formed within 3 hours.Under the condition of mixing petroleum hydrocarbon degrading bacteria and endophytic algae,the OMA has a long diameter of up to 2cm,and there are more oil droplets in the OMA,and the oil droplet size is smaller;and the petroleum hydrocarbon degrading bacteria and endophytic bacteria Compared with the mixed conditions of Algae,the OMA sedimentation rate is faster.The sedimentation rate of OMA on the first day is 4.57 mm/s.On the 12th day,the sedimentation rate is 6.31 mm/s,which is higher than the sedimentation rate on the first day.(6)Compared with bacteria or microalgae alone,the amount of OMA floc oil was significantly higher after mixing bacteria with microalgae,0.60 mg/mg and 0.65 mg/mg for endophytic bacteria and no endophytic bacteria,respectively.Less petroleum hydrocarbons in the aqueous phase,171 mg/L and 140 mg/L,respectively.In the case of adding a petroleum hydrocarbon degrading bacterium,the endophytic-free S.platensis has a higher content of TEP than that containing endophytic bacteria.(7)High-throughput sequencing results showed that when the algae were present,the diversity of bacterial communities in water was higher,and the proportion of species in OMA was larger.207 OTUs were observed in the two samples,of which 159 were common to both,accounting for 76.81%of the total OTUs.The dominant genus in OMA is Chloroplast,Oceanicaulis and Terasakiellaceae;the dominant bacteria in water are Chloroplast,Terasakiellaceae and Alcanivorax.Compared with the presence of bacteria alone,the abundance of Maricaulis and Alteromonas in OMA was significantly reduced,the abundance of Chloroplast,Phaeodactylibacter and Salinarimonas was significantly increased;the abundance of Vibrio and Alcanivorax was reduced in water,Chloroplast,Terasakiellaceae Abundance is significantly increased.