Study On Isolation And Characteristic Of Aromatic Oil Pollutants Degrading Strains

Oil is considered as the blood of the modern industries, because it is necessary for the development of society and economy. The pollution increases significantly due to the leakage of oil caused by waste disposal or accidental spills. In this study, three highly efficient oil-degrading(benzene, toluene and naphthalene) strains were isolated from aerobic sludge in the Membrane Bio-Reactor(MBR). Degradation kinetics,thermodynamics and characteristics of those oil-degrading strains were investigated.This study draw the following results through experiments and discussion:(1) Five benzene-degrading strains, four toluene-degrading strains and five naphthalene-degrading strains were isolated from aerobic sludge in the MBR.Moreover, the strains MB-2, MJ-1 and MN-5 had the best performance in degrading benzene, toluene and naphthalene, respectively. The degradation rates were 94.36%,93.67% and 99.38%, respectively, when the initial concentration of the pollutant was10 mg/L.(2) The results of 16 S rDNA PLR-RFLP revealed that the strain MB-2, MJ-1 and MN-5 were classified as Ochrobactrum, Stenotrophomonas and Sphingobacterium,respectively. Photomicrograph of the strains showed: MB-2 was rods with lengths of0.75-1.1 μm and diameters of 0.5-0.6 μm; MJ-1 was rods with longths of 1.9-2.4 μm and diameters of 0.21-0.3 μm; MN-5 was straight rods with longths of 2.5-3 μm, and o.26-0.6 μm pili were observed. Three strains were gram-negative bacteria.(3) The results of degradation kinetics showed that degradation of strain MB-2,MJ-1 and MN-5 conformed well to first-order kinetics. The degradation rate was inversely proportional to the initial concentration of targeted pollutant. The optimal temperature for the degradation of targeted pollutant were T=35, 30 and 35 ℃, and the Ea were 75.66, 17.27 and 91.60 kJ/mol, respectively.(4) Degradation efficiency of naphthalene for strain MN-5 was higher than that of benzene and toluene for strain MB-2 and MJ-2. The results of thermodynamics indicated that degradation of benzene and naphthalene for strain MB-2 and MN-5 can be completed easily. Values of Δ G were line with traditional specific enzyme catalyzed bio-reactions.(5) Orthogonal experimental and statistical analysis presented that the greatest degradation efficiency was obtained with the conditions of 35 ℃, pH=7 and inoculum size 15 %(v/v). The amounts of inoculum had the most significant impact on degradation rate, followed by temperature and value of pH, while surfactants had little effect on naphthalene degradation by strain MN-5.(6) When naphthalene concentration was 10 mg/L, co-metabolism degradation rate of strain MF-5 was 65.93, 43.02 and 36.31 %; respectively, corresponding to 10,20 and 30 μg/L CF. The degradation rate was inversely proportional to the initial concentration of CF. The inhibition effect was observed for strain MN-5 when higher CF concentration was employed, and the inhibiting effect was proportional to CF concentration.