Experimental Study On Bioaugmentation Degradation Of Oil-contaminated Soil In North Shann'xi

Many studies on bioremediation of oil-contaminated soil were reported at current time, and these mainly centered on the improvement of ecological environment of bacteria. The most important point was that most of the studies were conducted in the laboratory. Therefore, we adopted combined technologies that use weak electric field and bulking sgents to biodegradate oil-contaminated soils. Pilot-plant test was carried out to study the degradation of oil-contaminated soils. Based on the above studies, the optimal ecological conditions of oil-degrading bacteria in arid area of North Shann'xi were determined and lastly, optimal conditions for biodegrading the oil in the contaminated soils in North Shann'xi were obtained.The experiment results showed that, more farmed times can promote the degradation of the oil and the highest degradation rate is 92.6%, which is 32.35% higher than that of non-farmed soils. When bulking agents were added into the samples, different degradation rates were reached, because this can improve the ventilation of the soil, which provides sufficient oxygen for the microorganisms to get a better degradation rate of the oil-contaminated soil. And sawdust gave the best degradation rate of 87.96%, rice bran followed with 71.19%, and wheat straw ranked the last in 38.98%, all of which were better than that of no bulking agents-added samples(35.05%). 10min of radiation time and 300 V·m-1 of electric strength can be considered as the optimum conditions of the UE field to biodegrade the oil-contaminated soil and the removal rate was 12 percent higher than that of no radiation samples. By means of the GC-MS analysis, saturated hydrocarbons (C10-C40) contained in the oil-contaminated soil were almost completely degraded after 54 days of biodegradation. Therefore, bioremediation of oil-contaminated soils under the existence of the electric field and bulking agents was valid. The situ bioremediation results showed appropriate nutrients ratio was a key factor in degradation of the oil-contaminated soil, and nutrients-existing sample with degradation rate 73% was nearly 9 percent higher than that of no nutrients-added samples. Other results were also obtained, and more farmed times of samples were adverse to the degradation because of the arid area of north shann'xi. More farmed times are adverse to maintain of moisture in the soil. Therefore, the farmed period for the sample should be extended. Under the existence of sufficient moisture, anaerobic bacteria played a better role in the biodegradation of oil-contaminated soils, especially under the high pollution concentrations. The results showed that the best degradation rate was obtained when predominant bacteria are added and the soils are not farmed, and the degradation rate was 7.12 percent higher than that of bateria-added and farmed soils. The above results showed that anaerobic bacteria played a better role in biodegradation of oil-contaminated soil under high pollution concentrations. Still, this paper got 83.3%, 67.33%and 66.81% that were representing the degradation rate of the bottom, middle and upper oil-contaminated soils, respectively. And degradation rate of the bottom soil sample was 16.22 percent higher than that of the upper one. This further showed that moisture played a key role in the biodegradation of oil-contaminated soil.