The Study Of Bioremediation Of Petroleum Polluted Soil In Northwest Loess Area

Recently, exploration and production of oil in the Northwest China lead to a serious pollution of lands and water there. Bioremediation of petroleum-polluted soil in northwest loess area was studied in this paper through experiments in the laboratory scale and field experiment in a larger scale. Following conclusions can be made:1. The concentration of contamination in oiled soil influents the degrading ability of microorganism in bioremediation of oiled soil. In the lab scale experiment, when the pollution intensity were 0.71, 1.684 or 3.579g/kg, the corresponding removal rates of petroleum hydrocarbon were 92, 93, 98% after 28-day degradation under the condition of adding bacteria and digging soil. While in the field experiment, when the pollution intensity were 6.655, 12.767 or 15.34g/kg, the corresponding removal rates of petroleum hydrocarbon were 83.7, 56.2, 47.5% 79-day degradation. It was proved that a sound biodegradation effect could be achieved when the concentration of contamination in oiled soil was 3.579 g/kg～6.655 g/kg.2. After 24 days degradation, when inoculums size were 0, 5, 10, 15, 20, 25 and 30mL, removal rates of petroleum hydrocarbon were 48, 52, 65, 71, 75, 85 and 81% in the beginning of the experiment, while in the end of the experiment, the removal rates were79, 85, 83, 84, 82, 86 and 85%. It was shown that adding microbial agent had an obvious positive influence on the biodegradation of petroleum hydrocarbon in the beginning of the experiment. While in the end of the experiment, different inoculums sizes won't affect the removal rates of petroleum hydrocarbon obviously. Inoculating ways had no significant impact on the degradation of petroleum hydrocarbon.3. The removal rate of petroleum hydrocarbon increased during the improvement of the soil moisture content. The removal rate of petroleum hydrocarbon increased from 0.6% to 80.1% when the soil moisture content varied from 2% to 30% after 48 days degradation. The soil moisture content was an important factor for the degradation of Petroleum. Low soil moisture content had a prohibitive effect for the microorganisms' activity.4. Inoculated microorganism activity was improved a lot after adding nutrients to contaminated soil, and the removal efficiency increased significantly. Petroleum degradation efficiencies in soil of A, B, C, D groups after 27 days degradation were higher than comparison sample (24.8%) . In the following period, microorganism began to become inactive, and the petroleum degradation velocity was about zero.5. Raising the reaction temperature was good for the bioremediation. The soil's degradation efficiency under 37 °C was higher than 20 °C's, and petroleum degradation efficiency was 80.2% under in 37°C, but it was 59.6% under in 20°C after 48 days.6. The quantity of bacterium related to soil's electricity, and bacterium possessed negative electricity as a rule. More was quantity of bacterium; higher was soil's electricity. Usually quantity of microorganism was reflected by mensurating soil's electricity indirectly.