Preparation And Performance Evaluation Of Microbial Dispersant For Crude Oil

In the process of oil exploitation,transportation and utilization,Oil spill accidents often occur.Oil spill pollutes water,affects the growth of organisms and even human health.The main oil spills remediation includes physical,chemical and biological methods.The physical method has a good effect on a large number of oil spills,but its engineering volume is large,and the treatment is not thorough enough.Chemical method is to use chemical reagents to change the characteristics of oil spill and facilitate physical treatment.The emulsification of dispersing agent speeds up the natural weathering and degradation process of oil,so as to reduce the harm of spilled oil to the environment.Biological method is to use bacteria to degrade spilled oil and treat polluted water.Biological method is a measure that has little influence on environment.However,the practical application of chemical treatment agent has the problems of high toxicity,low efficiency and low biodegradability.Moreover,the treatment agent only changed the physical form of spilled oil in the water body,and did not achieve the real effect of eliminating oil spills.The bioremediation method has long processing cycle,low efficiency for oil spill treatment with wide area,large thickness and high viscosity,especially oil spill on the surface.This study combines the advantages of chemical and biological methods.A biological dispersant with high emulsifying and degrading activity for crude oil has been prepared,combined with chemical dispersant and petroleum degrading bacteria,which has better performance.By mixing two strains of petroleum degrading bacteria,which have strong ability of degrading oil and good adaptability,a bacteria community is obtained performing much better.Four kinds of four non-ionic surfactants with low toxicity and high emulsifying activity were selected to prepare a chemical dispersant with different proportions.With the influence of dispersant on the growth of bacteria and the emulsification rate as the evaluation index,a biological dispersant,has been successfully developed,in which the proportion of dispersant and complex microbial flora is the best.Finally,the emulsifying and degrading properties of dispersants were evaluated under different application conditions.The main achievements are as follows:(1)A microbial community with stronger degradation ability and better adaptability was constructed.The maximum degradation rate of crude oil is 56.90%in 20 days.(2)A chemical dispersant with low bio-toxicity and high emulsifying activity was prepared,and its emulsification rate for crude oil was 57.56%.The dispersant is composed of 5%emulsifier SES1,25%sorbitol laurate,10%sorbitol mono palmitate,50%diethylene glycol butyl ether.(3)A biological dispersant with good emulsification and degradation performance has been successfully developed.The biodegradability evaluation index(BOD5/COD)of the dispersant is 46.54%,indicating that this dispersant has good biodegradability.The average emulsification rate of this dispersant to crude oil is 57.61%,which is 27.19%higher than commercial dispersant.The average degradation rate of this dispersant to crude oil is 75.17%,which is 6.35%higher than commercial dispersant.All of these indicate that this dispersant has high application value in oil spill treatment.