Study On Degradation Effect Of Petroleum Pollutants By Bioremediation Based On Biostimulation And Bioaugmentation Strategies

As an important energy and chemical base in China,North Shaanxi produces a lot of oil pollution every year.As the most widely used and highly concerned bioremediation strategy at home and abroad,biostimulation? bioaugmentation and biostimulation–bioaugmentation system have great application prospects.At present,the research on the three remediation strategies generally exists in the study of the factors affecting the degradation performance and degradation rate.The study on the composition and diversity of soil microbial communities by different remediation strategies has gradually become a research hotspot.There are more studies on biostimulation and bioaugmentation in China,and less on the combined system of biostimulation–bioaugmentation.The purpose of this study was to study the degradation effects of three remediation methods under different conditions,and to grasp the effects of different remediation strategies on nutrient selection and soil microbial community composition and results.Three strains of petroleum degrading bacteria were identified by 16 S rDNA molecular biology.According to their physiological and biochemical characteristics,three strains were identified as Bacillus cereus T-04 KY852255,A-8(MF988690.1)Achromobacter ruhlandii and 1-1(MF988689.1)Bacillus halotoans respectively.Through the single factor experiments of pH,initial oil content concentration and salinity,the oil degradation effects of three strains of degrading bacteria under different conditions were evaluated respectively.The three strains had the best degradation effect at pH=7,and still had degradation effect in acidic environment,but the effect was not obvious,the degradation rate in alkaline environment was higher than that in acidic environment;the three strains had degradation effects at salinity concentration of 1.5%-2.0%.The degradation rate of strain 1-1 is still 31.85% at 5% salinity,which is suitable for use in high saline-alkali areas of northern Shaanxi.The degradation rate of three strains is the highest when oil content is 0.5%.The optimum degradation conditions of the three strains are determined as follows: pH=7,oil content is 0.5%,salinity concentration is 1.5%.There were significant differences between the three nutrient supplementation methods and the control group by biostimulation with organic,inorganic and mixed nutrient substrates.The effects of different nutrient substrates are different in different periods,the degradation of organic matter is higher in the early stage of degradation,the effect of biostimulation mixed nutrients is more obvious in the middle and late stage,and the difference is not obvious with inorganic nutrients.Through the bioaugmentation t experiments of single strain,two strains and three strains,we know the bioaugmentation effect of different strain combinations on petroleum pollutants.There are significant differences among the three strain combinations.The highest degradation rate of strain was 82.3% of D2(T-04+1-1),and 86.65% of the three strains.The highest degradation rate was found in the combination of two strains.Through the biostimulation–bioaugmentation system repair experiment,the degradation rate of inorganic nutrient substrates reached 89.4% on the 20 th day,which was higher than that of the two bacteria with the same nutrient substrates.In simulated soil remediation,180 days is used as a remediation cycle.The combined system of biostimulation,bioaugmentation and biostimulation–bioaugmentation reinforcement significantly improves the oil degradation rate.The degradation rate of the combined system of biostimulation–bioaugmentation of inorganic substrates was 96.7%.The concentration of petroleum pollutants in soil decreased from 10 000 mg/kg to 330 mg/kg,indicating that the removal ability of the three methods for petroleum pollutants in soil was ranked as follows: biostimulation–bioaugmentation combined system > biostimulation > bioaugmentationHigh-throughput sequencing was used to analyze the difference contribution of three bioremediation modes in soil microbial community diversity: biostimulation,bioaugmentation and biostimulation–bioaugmentation combined system.By Miseq sequencing,5 294 different OTUs were obtained in all samples.The minimum number of OTUs was 350,and the maximum number of soil groups was 1 105.Statistical results of generic classification level showed that the microbial composition in soil changed greatly after oil pollution.Lysobacter,Bacillus,Rhodococcus and Gordonia became dominant genera,which proved that oil-bearing soil could degrade oil through self-purification process.Comparing the bioremediation methods catalyzed by different nutrient substrates,it was found that organic substrates promoted Pseudomonas to become dominant community,and mixed nutrients promoted Ornithinebacillus to activate to a Alcaligenes certain extent.By comparing the biostimulation group,the biostimulation–bioaugmentation combined system repair group and CW group,it was found that the structure and composition of microbial community changed more prominently in the combined repair experiment.Rhodococcus? Nocardioides and Dietzia were the dominant bacteria in the three groups.The biostimulation group had the genera of Pseudomonas and the biostimulationn group had the genera of Planomicrobium?Pseudomonas ? Dietzia ? Rhodococcus and Arthrobacter belong to the genus Alcaligenes ?Planomicrobium and Psychrobacillus are distinct in the combined system repair group.The changed bacteria are common in the research reports.Especially the psychrotrophic bacilli found in the combined remediation group.Biostimulus treatment can maintain the balance of soil microbial community structure.The diversity of microbial community composition in the experimental group was richer than that in the control group.