| 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 and ground waters in the last two decades. Organic pollutants in soil could influence the normal function of the soil, contaminate groundwater, air and impact human health through the food chain and environmental quality. Therefore, it is necessary to take technical measures for cleaning up these pollutants in the environment. Biological treatment is considered to be one of the relatively low-cost and safe technologies. Therefore, in this work, we investigated the biodegradation of petroleum products by using Candida cultures in a batch system and the biodegradation of crude oil in contaminated loess soil was conducted under the laboratory conditions as well. Sorption/desorption onto the soil surfaces and aquifers matrix is one of the processes that control transport in subsurface, chemical transformation, and biological degradation of organic contaminants. So we chose a priority pollutant, 2,4-dichlorophenol, as an indicator to study such compounds sorption behaviors in natural loess soils and assess their bioavailability and biodegradation. The approach results were very important for environmental impact assessment and bioremediation technologies in Northwest China, where vast and thick loess soils are expended in topography.Chapter 1.Advances in the Research on Bioremediation of Petroleum Contaminated SoilA review is reported with 70 references about bioremediation of petroleum contaminated soil. It deals with the concept of bioremediation, biodegradation mechanisms, bioremediation techniques and influencing factors, meantime the progress using bioremediation for site restoration and their applications on the bioremediation, and the future research needs for development bioremediation of petroleum contaminated soil were involved.Chapter 2.Degradation of the Petroleum Products by Two Yeast Strains in AquaticEnvironmentIn this section, the abilities of two yeast strains, Candida lipolytica and Candia nigosa for removing the mixture of diesel and crude oil were studied in a batch mode under the laboratory conditions. The results suggested that the removal rate of petroleum products was influenced by the environmental factors. The slight addition of complex carbon source and other nutrients was capable of significantly increasing the oil removal efficiency. The oil degradation occurred at the oil concentrations ranging from 0.025 to 0.5%, while the highest efficiency of above 65% for 10-day culture was at the oil concentration 0.1%. Both strains tend to occupy acidic near neutral environment, which is close to the natural condition. Under a favorable condition: the initial oil concentration of 0.1 %, at pH 6-7 and addition of the nutrient medium, the decrease of oil occurred after 2-day culture and the oil removal ratios increased with the increase of incubation time and the removals of oil were 70.2%, 75.0% and 82.8% after 15-day culture for the two yeast strain and the mixed culture, respectively. However, the maximum rates of oil removal were appeared between 2 and 7 days. In general, under proper condition, the oil were degraded by the two strains and mixed culture of them significantly, so it may be a possible option to introduce the strains to stimulate biodegradation of petroleum pollutants in both aquatic and terrestrial contaminated environments.Chapter 3.Biodegradation of Crude Oil in Contaminated Loess SoilIn this work, biodegradation of the crude oil in contaminated loess soil by mixed culture of two yeast strains was investigated under the laboratory conditions. To assess the effects of nutrients and soil oxygen content, the three treatments with different supplying of nutrients and other four treatment approaches with...
|
PDF Full Text Request