Screening Of High Efficient Oil Degradation Bacterium And Scaling Effects On The Degradation Of Crude Oil By Pseudomonas

With the rapid development of economy,the demand of petroleum is continually increasing in recent years.Water injection technology is widely used,with large amounts of oily water producing in this situation.As we all know,the best way of treatment of wastewater is that inject it into the oil well during the process of petroleum producing.In many wastewater treatment methods,the biodegradation of water was becoming the focus of this research both at home and abroad,because it' s mild conditions and stability of water quality after treatment.Due to some features of oily water,such as the strong corrosion and scaling,deposition of scale on the surface of microbes and so on,water injection technology seriously affect the efficiency and effectiveness of the process in microbial degradation of crude oil wastewater.Therefore,studying the scaling effects on microbial degradation of sewage and taking the appropriate measures to maintaining microbial stability of the treatment process is of great significance.This thesis based on simulation of oily water to studying on strong scaling tendency,screening the high efficient oil degradation bacterium,studying the impact of scale on degradation of crude oil-degrading bacteria using transmission electron microscope to analyse the degradation process of salt scale on the micro-cells of strain.In the paper,Six crude-oil-degradation bacteria were isolated from oil-contaminated farmland in Wuqi county of Shaanxi province.The growth and degradation characteristic of the six strains were studied through morphological observation,physiology biochemistry experiment,molecular biological techniques(16SrDNA)and GC-MS etc.The result showed that six oil-degradating bacteria were:P1(Microbacterium oxydans),P2(Ochrobactrum intermedium),P3(Alcaligenesfaecalis),P4(Brevibacillus laterosporus),P5(Stenotrophomonas)and P6(Pseudomonas aeruginosa),respectively.Through cultivating and domesticating about seven days,the degradation rate of crude oil were 83.47%,81.60%,85.30%,81.60%,84.58%and 85.96%;GC-MS analysis result showed that the strains'degradation of long carbon chain hydrocarbon is remarkable.At the same time,they all can produce a certain amount of surface active substances in the process of degradation.Pseudomonas aeruginosa was selected as the experimental strains bacteria in later experiments.There are many factors can affect the degradation efficiency,for example,different pH,shaking speed,inoculum,crude content and salinity.After a series of experiments,the optimal degradation conditions is:pH=7.0,shaking speed =180R/min,2%oil content,0.5%salinity.In that condition,the degradation rate reach to 91.7%.Later experimental results show that the inorganic scaling(CaSO4)reduce the degradation rate of pseudomonas aeruginosa.TEM(Transmission electron microscope)results indicate that CaSO4 would deposit on the surface of the pseudomonas aeruginosa bacteria,resulting in the bacteria cell ruptured and died.