【作者】 张文；

【导师】 黄国和； 李建兵；

【作者基本信息】 华北电力大学 ， 能源与环境工程， 2012， 博士

【摘要】 石油是一类具有致癌、致畸和致突变性的有机污染物,随着其在国防、航天、工业等重要领域的广泛应用,大量的石油及其制品由于各种途径进入土壤和水环境并对生态与人类健康造成严重危害。微生物修复技术因其经济及有效性而成为一种最具发展潜力的治理石油烃污染的技术,它是微生物催化降解有机污染物从而去除或消除环境中石油类有机污染的一个受控或自发进行的过程。由于石油烃的疏水性和环境的复杂性等原因,自然条件下微生物降解速度较慢,可采取多种措施强化生物修复这一过程。本文考察了生物表面活性剂鼠李糖脂溶液的表面张力在极端环境下的稳定性及粘土、壤土及砂土三种不同土壤类型对其的吸附作用。本文证明鼠李糖脂对原油饱和烃(SAT)和多环芳烃(PAH)组分具有明显的增溶作用,并能有效促进污染物质的解吸。本文在实验基础上采用投加表面活性剂、提供微生物生长繁殖所需条件(O2、营养元素)和投加外源微生物等方式对石油类污染土壤及地下水进行修复。本文其次分析了表面活性剂及各环境因子对石油类有机污染土壤的生物降解过程的影响,并对微生物降解进行一级动力学分析,为高盐度的含油土壤修复提供了理论依据和数据支持。最后通过地下水原位修复中试装置,结合基础实验数据和中试实验数据,建立了地下水饱和带石油类污染物的迁移及微生物修复模拟模型。本文主要结论如下：1.生物表面活性剂鼠李糖脂具有优良的表而活性,并显示出良好的环境适应性。其具有较低的临界胶束浓度和极低的表面张力。通过对不同盐度和pH条件下鼠李糖脂溶液浓度和表面张力变化关系的拟合,结果表明该表面活性剂在不同盐度和酸碱度环境下其溶液的表面活性不易受盐度和pH的影响,因此在含盐量高、含油量高、酸碱性不同的土壤及地下水污染场地修复中具有较好的稳定性和较强的实用性。另外,鼠李糖脂施用环境中土样粒径越大,土壤有机质含量越小,鼠李糖脂损失量就越小(鼠李糖脂在壤土、砂质壤土和砂土中的损失量分别为75.0%、66.7%和50.0%)。2.原油组分SAT和PAH在生物表面活性剂鼠李糖脂溶液中有显著的增溶作用,与水中SAT和PAH的溶解量相比分别提高了20倍和84.6%。对鼠李糖脂浓度-液相SAT浓度进行线性拟合,发现表面活性剂鼠李糖脂对SAT各组分的溶解限为0.04%左右。鼠李糖脂溶液浓度增加对石油中PAH组分的增溶能力影响趋势与SAT组分相同。由于多环芳烃强烈的疏水性,鼠李糖脂溶液对其增溶能力远低于对饱和烃组分的增溶能力。对环境因素盐度和酸碱度的正交实验考查结果显示鼠李糖脂浓度是影响SAT和PAH溶解效果的主要因素。正交实验还表明,鼠李糖脂浓度、pH值和盐度在SAT和PAH的溶解过程中存在两两交互作用,且盐度的增加削弱了SAT的溶解,而碱性的增加有利于SAT和PAH的增溶。3.大于临界胶束浓度的生物表面活性剂鼠李糖脂溶液有效促进了原油组分SAT和PAH的解吸,土样类型不同,两种,组分的解吸率也不同,砂土有机含量低且颗粒比表面积小从而导致吸附的石油组分会更易被解吸。当鼠李糖脂浓度为0.02%和0.04%时SAT和PAH的解吸率甚至低于去离子水中两种组分的洗脱率,经分析这种现象是由于溶液中的鼠李糖脂优先被土壤颗粒吸附,吸附相的鼠李糖脂影响了SAT和PAH在土壤上吸附及分配过程,从而导致石油在土壤上的吸附量增加。鼠李糖脂的存在对两种土样中石油饱和烃的去除率均有一定积极作用,且当鼠李糖脂浓度达到0.08-0.1%时其解吸效果较好。相较于SAT来说,PAH疏水性更强,且环数越高结构越复杂的PAH疏水性和吸附能力越强。pH值的变化通过改变土壤物化性质从而改变土壤-石油-鼠李糖脂系统中石油污染物的吸附状态,且呈弱酸性的鼠李糖脂溶液有利于促进SAT和PAH的解吸。盐度的增加对土壤中SAT和PAH的解吸有一定的影响,且因土壤成分不同其解吸规律不同。4.通过控制微生物降解石油污染土壤实验过程中的温度、湿度及氧气等重要因素,利用正交方法设计实验,考察了土壤类型、表面活性剂和石油初始浓度等因素间交互作用对土著微生物降解土壤中石油烃的影响。正交试验中所有样品的石油烃降解率达到66.21-94.00%,比添加HgCl2以控制微生物活性的空白对照样品高出了28.44-56.23%,说明石油烃在土壤中的减少主要是由微生物降解引起。通过气相色谱-质谱联用仪的测定,确定了与重质烷烃相比,轻质烷烃更容易被微生物降解。实验结果表明土壤类型是微生物降解过程中的最重要因素,土壤颗粒对石油分子的吸附是微生物降解石油烃的瓶颈。表面活性剂的加入有利于改善油-水-微生物细胞界面的接触行为,通过增强细胞膜疏水性、增强疏水性有机物的亲水性等方式加快了微生物对油类污染物的利用速度及降解速率5.土壤-油-微生物系统中,表面活性剂添加浓度为两倍临界胶束浓度的土壤样品中微生物对石油烃的降解速率最大,达到0.0866d-1,说明适量的生物表面活性剂鼠李糖脂的添加会促进石油烃的微生物降解,但表面活性剂浓度过高反而会影响其使用效率。盐度的增加使得石油类有机物在水相中溶解度减小,从而增大其在土壤颗粒上的吸附量,且.盐度越高越会对微生物产生毒性,从而降低其对有机污染物的降解能力。本实验证明盐度的增加对微生物降解石油烃污染物具有抑制作用,系统中NaCl浓度分别为0.2、0.4mol/L时,微生物降解速率约为不加盐样品的1/2、1/4。值得肯定的是,添加生物表面活性剂鼠李糖脂能有效促进含盐量高的土壤中有机污染物的降解。6.设计了砂箱土壤及地下水物理实验模型,并构建了一套微生物处理系统,利用Visual MODFLOW进行了数值模拟,对实验数据和预测数据进行拟合且拟合结果较好。实验证明生物表面活性剂鼠李糖脂能有效改进地下水饱和带有机污染生物修复技术,对柴油等有机污染去除率较高,修复效果显著。更多还原

【Abstract】 Crude oil can enter the soil and groundwater system through a variety of pathways, such as leakage of underground storage tanks and accidental spill during the exploration, production, and transportation process. Due to the carcinogenicity, teratogenicity and mutagenicity of petroleum hydrocarbons, crude oil contamination can result in serious ecological and human health problems. Therefore, the effective remediation of crude oil contaminated soil and groundwater is of critical importance. Bioremediation has been proved to be an effective and low-cost treatment option for the cleanup of organic pollution. However, the low bioavailability of petroleum hydrocarbons in crude oil and the environmental complexity can lead to slow biodegradation rate. Various measures can be taken to enhance the bioremediation of crude oil contaminated soil and groundwater. This study was aimed to investigate the surfactant enhanced bioremediation of crude oil contaminated soil and groundwater system. The influence of environmental factors on the surface property of bio-surfactant rhamnolipid and its sorption onto different soils, such as clay, loam and sand, were examined. The impacts of bio-surfactant on the solubility of saturated and polycylic aromatic fractions in crude oil, and on the desorption of these fractions from soil, were investigated. The effects of surfactant and various environmental factors on the bioremediation of petroleum hydrocarbons in crude oil were analyzed. The impact of salinity on the bioremediation of crude oil contaminated soil was also examined in order to provide theoretical basis and data support for the remediation of soil contaminated with both salt and crude oil, which is a common problem in the oil and gas industry. A simulation model was lastly developed to investigate the bioremediation of crude oil contaminated groundwater based on the experimental data obtained from a sand box model. The main results of this thesis were summarized as follows:(1) Impact of environmental factors on the surface property of biosurfactant:a series of experiments were conducted to test the effect of pH, salinity and soil adsorption on the surface property of rhamnolipid. The results indicated that pH showed no obvious effect on the surface tension change of rhmnolipid, but salinity had a positive effect on changing the surface tension of rhamnolipid. The pH and salinity didn’t affect the critical micelle concentration (CMC) of bio-surfactant solution. The sorption loss of rhamnolipid was calculated as75.0%,66.7%, and50.0%for loam, sandy loam, and sand, respectively, indicating that soil properties such as particle size and organic matter had significant impact on bio-surfactant sorption which may generate negative effect on remediating oil contaminated soil.(2) Impact of biosurfactant on the solubility enhancement of saturated aromatic fractions (SAT) and polycyclic aromatic fractions (PAH) in crude oil:It was found that the bio-surfactant can remarkably enhace the solubility of SAT and PAH in crude oil. However, when the biosurfactant concentration approached a certain level (i.e. mass-0.04%), the solubilization effect of these crude oil components was weakened. The solubility of PAH was much lower than that of SAT because of its strong hydrophobic feature. Based on the Taguchi experimental design method, a series of laboratory experiments were conducted to examine the impact of rhamonipid concentration, pH, and salinity on the solubility of SAT and PAH fractions. The results showed that the rhamnolipid concentration was the most important factor influencing SAT and PAH solubility. The results also showed that these three factors and their interactions had obvious effect on solubility of SAT and PAH In this study, the SAT solubility decreased with increasing salinity, while the variation of salinity had little influence on PAH solubility. And the increasing pH in the alkaline range had a positive impact on solubility of SAT as weli as PAH.(3) Impact of biosurfactant on the desorption of saturated aromatic fraction (SAT) and polycyclic aromatic fraction (PAH) from crude oil contaminated soil: adding rhamnolipid to the crude oil-water-soil system at concentration above its critical micelle concentration (CMC) value, can benefit the desorption of SAT and PAH fractions from soil. The sandy soil was associated with less amount of rhamnolipid adsorption. The desorption of these two fractions were much lower when rhamnolipid solution concentrations were mass-0.02and0.04%. The desorption of both fractions were most significant when rhamnolipid concentration increased to mass-0.08～0.1%. The change of pH can have distinct effect on rhamnolipid performance concerning its own micelle structure and soil properties. With the increase of salinity, the solubilization and desorption of petroleum hydrocarbon fractions were more significant due to the difference of soil physical and chemical properties.(4) Impact of environmental factors on the bioremediation of crude oil contaminated soil:based on the Taguchi experimental design method, a series of laboratory experiments were conducted to investigate the impacts of five environmnetal factors on the remediation efficiency of crude oil contaminated soil. They include the soil type, the type of surfactant, the surfactant concentration, the initial petroleum hydrocarbon concentration in soil, and the soil salinity. It was found that there was a distinct decline of soil total petroleum hydrocarbons (TPH) concentration when using surfactant during the bioremediation period of30days. TPH degradation efficiencies of Taguchi experiment were66.21-94.00%which was much higher than the control of28.44-56.23%. The analysis of variance (ANOVA) indicated that the five study factors had little effect on the soil TPH biodegradation except for soil type on day20and day30. The interaction effect between the five factors was not significant. The soil type was observed to be the most important factor affecting the bioremediation efficiency, but the impacts of other four factors were enhanced in the later stage of bioremediation.(5) Impact of biosurfactant concentration and soil salinity on the bioremediation of crude oil contaminated soil:a series of laboratory experiments were conducted to further examine the impact of biosurfactant concentration and salinity on TPH removal from crude oil contaminated soil. Rhmnolipid was selected as the study biosurfactant. It was found that the remediation was more effective with the concentration of bio-surfactant just slightly above or below its CMC (i.e.,0.5,1,2CMC). The most effective remediation that occurred was with rhamnolipid concentration in soil solution of2CMC, and the TPH biodegradation rate constant was0.0866d-1. Salts had a negative impact on soil TPH degradation. Consequently, the rhamnolipid can significantly increase bioavailability of TPH to soil microorganisms, and salts should be removed first before applying bio-surfactant for the remediation of soils contaminated with both crude oil and salts.(6). Experiments and simulation of bioremediation for diesel contaminated groundwater:a sand tank box model was established to conduct experiments on the bioremediation of diesel contaminated groundwater so that a numerical model can be developed to simulate the remediation process. The Visual MODFLOW was applied to simulate and calculate the diesel concentration distribution in the saturated zone. It was found that the experimental data obtained from the sand box modeling matched very well with the prediction values obtained form the Visual MODFLOW model. The results proved that bio-biosurfactant enhanced bioremediation system can quickly and effectively remove the organic pollution from the groundwater zone.更多还原