| With the development of oil industry and the growing rapidly national economy, the oil pollution becomes urgent repaired. Many physical and chemical methods have limitations due to their high costs and then, lower costs and less pollution, the advantages of biological treatment technology owns, become a research hotspot. Constantly study shows that, biological treatment technology has strong industrial bioremediation feasibility, social and economic benefits.In this study, microbial remediation was mainly studied, by screening high efficient microbial degradation bacteria, and their identification was carried out, and their degradation characteristics and the application were also studied. The results were followed by:1) Fifteen strains with distinctly colony characteristics were obtained by domestication, separation and purification experiment. Nine distinctly strains were isolated by screening with the first step. By further oil degradation test, two high effective oil-degrading strains were screened. The nine strains, that got by screening, had some effects on the degradation rate of petroleum hydrocarbons. The degradation rate of different strains was significantly different. The scope of the degradation efficiency value was from 28.7% to 59.8%. By multiple comparison analysis, two highly efficient petroleum degrading strains, named Y-7 and Y-9 were screened and isolated from petroleum-contaminated soils.2) By first studying colony morphological, then physiological and biochemical characteristics, Y-9 was preliminary identified as Bacillus sp., also with molecular identification of Y-7, it was identified as Pseudomonas sp. for certain.3) Under the test conditions, while the pH value was near 7.0, the oil degradation rate was found to be best, respectively was 68.7% and 74.5%, in acidic or alkaline conditions, the oil degradation rate was less than neutral environment. The effect of culture temperature on the two cell growth and the oil degradation rate were huge. The best culture temperature was 35℃, which made the oil degradation rate the highest, respectively was 73.1% and 69.6%, the biomass and oil degradation rate had a positive correlation. When the initial oil concentration was higher than 400 mg/L, the Y-7 oil depredation was decreased from 69% to 49%, while Y-9 had no obvious change. To beneficial to petroleum biological treatment, we can control the petroleum substance concentration not more than 400 mg/L. The number of inoculation had little effect on oil removal rate, the best quantity of inoculation was 2 %, it increased the degradation rate, at the same time, and the cost was the least. The promotion function of Twain 80 remains to be studied on. The strength of selected nitrogen source for petroleum degradation study was in the order: (NH4)2SO4 > NH4Cl > NH4NO3 > NaNO3, we can regard (NH4) 2SO4 as the best medium for nitrogen source. The petroleum degrading strains isolated in this study will be good candidates for bioremediation of petroleum-contaminated soils, and the analysis of the degradation characteristics will offer a valid scientific basis for better bioremediation of petroleum-contaminated soils.4) The oil degradation rate of the mixed bacteria Y-7 and Y-9 was significantly higher than a single strain Y-7 or Y-9, the degradation rate of the mixed bacteria was 87.1% after culturing 3 days. The single strain was increased respectively about 44% and 37%. Add the single strain or mixed bacteria Y-7+Y-9, the COD values in the bioreactor were all decreased, the COD value of them were dropped respectively from 271.4 mg/L to 177.9 mg/L and 177.8 mg/L after culturing four days. As strains synergies between the mixed bacteria is better than a single strain. Added a single strain or mixed bacteria Y-7+Y-9, the pH values were all changed to some degree, the range was not large, from 7.63 to 7.95.
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