| Along with the develope of oil pollution treatment technology, pople realized more and more clearly that the biological treatment technology is a cost-effective, highly active and the most environmentally friendly method. The research of oil-degrading microorganisms became a project which the environmentalists pay more and more attention to.This article summarized the oil pollution hazards, recovery technique of oil pollution, immobilization technology on bacteria, research on degradation kinetics and interrelated research progress both home and abroad. Emphasized on expound of microbiological recovery technique of oil pollution.In this study, we separated4strains that had the ability to degrading oil from long term petroleum-contaminated soil nearby the Shanghai Oil Refinery. Among these strains, the H-1strain had the highest degradation rate, more than20%after7days. Gram-staining results showed it belongs to gram-negative bacillus. By identifying the stems with Biolog Microstation System, it showed that the strain belonged to Bacillus sp.Optimizing oil degradation conditions of the H-1strain, the results showed that when the culture temperature at37℃, initial concentration of oil1g/L, NaCl concentration15g/L and pH7.0, the strain’s degradation rate reach maximum. Among them, the temperature had the highest influence on degradation rate, then initial concentration of oil and pH, the NaCl concentration had the lowest influence. The influences on degradation rate of four factors were all indistinctive. Use sodium alginate (SA)-calcium alginate (CA) method to immobilize the experimental strains. Testing performance like molding effect, mechanical strength, permeability and broken rate of gel microspheres, we preliminary determined the range of immobilizing condition like SA concentration, bacterial suspension addition and cross-linking time.Observe the micro-mechanism of gel microspheres using scanning electron microscope. It showed that the microsphere’s surface densification can effectively prevent the leakage of bacteria cell and the macromolecule toxic substance entering the microspheres to harm the bacteria cell. The microsphere’s inside was loosing reticular structure, plentiful extent of porosity, was propitious to transport oxygen, water and substrate. It also can provide sufficient growing space for embedded degrading bacteria, providing advantages for growth and propagate of bacteria inside the carrier.Use the degradation rate of oil as the experimental index to carry out four-factor orthogonal test at three levels. The result showed that the best immobilized condition was SA concentration7.0%, bacterial suspension addition75%, CaCl2concentration2%and cross-linking time24h. Among them, the SA concentration had the biggest influence to the degradation rate, then bacterial suspension addition and cross-linking time, the CaCl2concentration nearly had no influence. The influences on degradation rate of four factors were all indistinctive.Inoculate equal free strains and immobilized strains into mineral medium which added oil, testing residual oil concentration inside the medium every2days and fitted the oil’s degradation velocity using Monod equation. Results showed that when there was lower oil concentration, its degradation kinetics conformed to the Monod equation’s Linear simplify shape. The free strain’s half-saturation constant was Ks=85.82mg/L, and maximum reaction rate was vmax=24.09d-1. Immobilized strain’s half-saturation constant was KS=52.33mg/L, and maximum reaction rate was vmax=44.05d-1.In the degradation kinetics equation, the higher the vmax and the lower the KS, the easier to have the substrate degraded. Compared the parameters of free strain’s degradation kinetics equation with the immobilized strain’s, it could be seen that the immobilized strain’s degradation efficiency was much higer than the free strains. From the fitting parameters, it could be known that the oil, which is one of important environmental pollutant, could be degraded effectively under suitable conditions. |
PDF Full Text Request