The Influence Factors Of Bioremediation Of Petroleum Polluted Soil In Northwest Loess Area

With the development of petroleum industry, petrochemical pollution becomes one of the pervasive problems, which is faced by all industrial countries. It is also one of the critical environmental issues in the Northwest China, where exploration of oil fields and leakage of oil pipes have caused the contamination at a large area of agricultural land in the last two decades. After soil suffers petroleum pollution, the effects of petroleum degradation speed is excluded besides the petroleum degradation microorganism and the physical—chemical property of contaminant, still gets the influence of environmental factor and so on. If we want get higher petroleum degradation efficiency and the best disposal effect, we must carry out the research for the biological degradation ecological condition of petroleum with discussing.Under this background highly efficient petroleum-degrading bacteria were screened, isolated from oil-polluted soil, and they have been identified primarily. The main environmental factors which affect its degeneration performance were further studied in this passage.The main conclusions of the study were as follows.1. Taking pollution strength as a important factor to study the biodegradation process of oil-pollutants in the soil. It has been found that the biodegradation would accelerate with the increasing number of pollution strength in the limited pollution strength.2. The plowed soil that affect the biodegradation process of oil-pollutants in the soil were studied, The experimental results indicated that the plowed soil would accelerate the biodegradation.3. The PH value and conductivity that affect the biodegradation. process were studied. The experimental results indicated that the PH value variable range is 6～7 in the biodegradation process. The petroleum degrading bacteria was highly efficient in the PH value variable range 6-7.4. The changing potential of the oil-pollutants in the soil was studied in the biodegradation process. In the primary biodegradation, the rate of the biodegradation is faster than the late of the biodegradation process.5. The experiment was carried out to investiage the effect of bulking agents on the rate of biodegradation in the soil. Adding bulking agents increased the rate of biodegradation compared to the treatment without bulking agents. The rate of biodegradation was higher intreatment with bran coat over sawdust and rice-straw. The content of petroleum was reduced by 90% with bulking agents incubated for forty day with the room temperature.6. Adding some water in the soil can promote the biodegradation. The experiment proved that the best proportion is about 25%.7. GC-MS was used to analyse the oil-pollutants in the soil. It has been suggested that most of the ortho-structure alkane in the soil changed to small molecule alkane or fatty acid. But it is not suitable for the cyclic hydrocarbon and aromatic hydrocarbon through biodegradation.8. The experiment was carried out to investiage biodegradation in low temperature environment. The rate of biodegradation in winter is much lower than in high temperature. The best of the biodegradation rate is only 21.3%. So we suggest that the biodegradation be carried out in summer.