共查询到19条相似文献，搜索用时 187 毫秒
1.
通过一维砂柱实验研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对空气扰动技术(air sparging,AS)修复氯苯污染地下水的强化效果.结果表明,SDBS的加入降低了地下水的表面张力,减小了水气两相毛细压力,从而提高了地下水中的空气饱和度.当曝气量为100 mL/min,地下水的表面张力由72.2 mN/m降至49.5 mN/m时,地下水中空气饱和度由13.2%提高至50.1%,而后随着表面张力的进一步降低,空气饱和度不再提高,反而有小幅下降.通过污染物的去除实验发现,SDBS的加入大大提高了氯苯的去除率,且去除率的变化与空气饱和度的变化趋势基本相符.因此,表面活性剂的加入可以作为空气扰动技术一种十分有效的强化手段. 相似文献
2.
通过实验室一维砂柱模拟研究了不同影响因素下空气扰动技术(air sparging,AS)修复氯苯污染地下水的效果,包括介质渗透性、曝气方式、共存污染物、残余饱和态氯苯。结果表明:介质渗透性极大地影响着AS的效果,渗透系数越大,去除效果越好。对渗透系数为10-5m/s数量级及其以下的介质应用AS较为困难;在曝气时间相同的情况下,对于渗透系数为5.1×10-4m/s的中砂,脉冲曝气较连续曝气效果好,对于渗透系数为6.2×10-3m/s的粗砂,2种曝气方式效果相仿;苯和氯苯共存时各污染物的去除存在协同作用;AS对残余饱和态氯苯的去除存在着明显的拖尾效应。 相似文献
3.
生物曝气技术对石油类污染地下水的修复效果及去除机制 总被引：1，自引：0，他引：1
针对东北某石油污染场地水文地质条件进行模拟,按照试验场地地层现状进行实验室缩放,研究微生物在含水层介质为砾砂、粗砂和中砂中的迁移速度以及含水层介质吸附的微生物量。选取苯和二甲苯作为目标石油污染物,研究生物曝气技术对被污染地下水的修复效果及其去除污染物的机制。实验结果表明:微生物在介质中的迁移速度从大到小为砾砂、粗砂、中砂;介质吸附微生物量的顺序从大到小为中砂、粗砂、砾砂;生物曝气4个月后,苯和二甲苯去除率分别为86.4%和81.7%,BS对中砂层中的苯和二甲苯去除效果好于砾砂层和粗砂层,苯的去除效果好于二甲苯。由挥发机制去除的污染物为46.24%,生物降解去除的污染物为36.98%,BS技术可以有效去除地下水中石油类污染物。 相似文献
4.
地下水曝气工程技术研究——以德州胜利油田地下水石油污染治理为例 总被引：5，自引：0，他引：5
为了研究地下水石油污染现场曝气治理效果,在胜利油田石油开采区进行了地下水现场曝气治理技术研究。采用溶解氧浓度法研究了曝气操作条件(曝气深度、曝气压力和曝气流量)对地下水石油污染曝气治理技术的影响。实验结果表明:在相同曝气压力和流量下,曝气深度越大,影响半径越大,但影响区内的气流分布越稀疏;相反,曝气深度越小,则曝气影响半径越小,但在影响区内空气流线分布越密。气流分布密度和曝气影响半径随曝气压力和流量增大而增大,但存在一个最佳限值;现场曝气存在气流分布不对称现象,是由于土壤介质的渗透性不均匀所致。地下水曝气技术对地下水石油污染治理效果显著,但曝气操作条件对该技术影响较大,需根据地质条件通过现场曝气试验确定。 相似文献
5.
为进一步研究地下水曝气原位修复技术的影响因素,采用室内实验的方法系统地研究了含水介质对原位曝气技术修复地下水污染的影响。研究结果表明:大量水相中的柴油在曝气的开始阶段被去除,随着时间的延长,污染物去除率不断增加,但增加的幅度逐渐减小。污染物去除率与时间关系曲线符合对数曲线规律,相关方程为y=alnx+b,R2=0.802 4～0.907 1,相关性较好。含水介质的渗透系数对地下水污染修复的影响较大,渗透系数与污染物的去除率基本呈正相关关系,渗透系数越大,污染物的去除率越大;含水介质密度与污染物去除率基本呈负相关关系,含水介质密度越大,污染物的去除率越小。 相似文献
6.
《地下水》2017,(3)
地下水是水资源的重要组成部分,若被污染,则再难于恢复到原来的状态,探讨分析地下水污染物运移特征对于保护地下水资源具有重要意义。本文以南通某沿海经济开发区为例,对研究区内的地下水和包气带进行监测,并运用地下水数值模拟软件GMS,对研究区典型污染物运移特征进行模拟预测,探讨分析土壤吸附作用对污染物运移的影响。结果表明,污染物迁移距离和运移面积与污染物源强呈正相关关系,考虑吸附作用时,COD和氨氮污染物中心点浓度分别降低29.9%和29.8%,最大迁移距离分别降低20.4%和24.9%,超标面积分别降低32.4%和29.2%,吸附作用对污染物具有显著的削减作用。 相似文献
7.
`土壤-地下水耦合数值模拟是定量刻画水流和溶质运移的主要手段。现有大范围场地尺度的研究受到数据采集难度及模拟计算量的限制,多是将土壤和地下水分成两个系统,这种方式不利于模型之间的计算反馈,易出现计算误差,因此将土壤和地下水作为整体系统研究具有重要意义。为精确刻画实际场地土壤-地下水系统中污染物迁移规律,揭示变饱和反应溶质迁移模型的参数敏感性,以某铬污染场地为研究对象,基于现场试验及前人研究所获数据,采用Galerkin有限元法建立三维土壤-地下水模型,定量描述六价铬在土壤-地下水中的迁移规律。在此基础上,通过改变补给条件,研究潜水面在土壤-地下水系统中的波动。并讨论阻滞系数和反应常数对溶质运移的影响。结果表明:在土壤中,污染物最大水平迁移距离为场地东南侧300 m;地下水中污染晕最大分布面积约为1.632 km2;垂向上土壤中的六价铬仅需15.6 h即可下渗至潜水面,第6天贯穿含水层。当潜水面随着补给量变化而波动时,地下水中六价铬会随水流进入土壤,影响土壤中污染分布。对溶质运移参数的讨论显示,当反应常数由0增大至10?6 s-1时,迁移出场区边界时地下水中污染物浓度约减少2000 mg/L,较难迁移至涟水河。基于FEFLOW的数值模型,能够解决各系统之间交互性差的问题,提供较为精确的模拟结果。 相似文献
8.
9.
选取某农药厂旧厂区为试验场地,考察化学氧化技术异位处理地下水非水相有机污染物的运行效果。基于小试研究,确定高锰酸钾、高铁酸钾、芬顿试剂以及次氯酸钠4种氧化剂在中试试验中的适宜投加量。中试结果表明,当进水流量为1.0 m^3/h时,不同氧化剂对于常规水质指标及特征有机污染物的去除效果存在差异性。总体而言,四种氧化剂对于中长链石油烃类污染物(C10-C36)的去除率可达20%~70%,但对氯代烷烃类污染物的去除效果低于20%;高铁酸钾和次氯酸钠分别对于苯酚类和多环芳烃类污染物的去除效果较好(70%~100%);芬顿试剂对各类污染物均有显著氧化效果,其中对于短链石油烃(C6-C9,去除率20%~40%)、苯系物(去除率40%~90%)的去除效果高于其他三种氧化剂。研究不同氧化剂对于多组分有机污染地下水的处理效果,为将化学氧化技术应用于此类污染场地提供了理论和技术支持。 相似文献
10.
通过室内水平砂柱内的咸淡水驱替试验,以高岭土、伊利石和蒙脱石、二价汞离子(Hg2+)和苯酚(C6H5OH)为例,对粉细砂的水敏性特征进行了研究。结果表明:高岭土和伊利石含量对粉细砂水敏性的影响不大,即使含量达到10%(质量比),渗透系数也仅下降1个数量级,而当蒙脱石含量为3%(质量比)时,砂柱渗透系数下降已经超过2个数量级,含量超过4%(质量比)时,水流已经无法通过;在高速水流剪切力作用下,31.68%二价汞离子(Hg2+)和55.71%的苯酚能够被有效去除,而水敏性过程中的颗粒释放与迁移作用能够将绝大部分残余的二价汞离子(67.55%)和苯酚(43.43%)挟带出粉细砂柱。单纯的水力作用对两种污染物的去除率差别较大,原因是砂柱中粘土颗粒表面带有负电荷,使得带正电的二价汞离子(Hg2+)大量被吸附,导致其滞留于砂柱之中的比例大于苯酚。故利用粉细砂的水敏性特征可在含水砂层中建立防渗帷幕、去除重金属和有机污染物。 相似文献
11.
Air was injected through a well in a thin transparent tank filled with saturated glass beads to study how the size and air
saturation of air sparging plumes are affected by particle size and gradation; operational parameters such as injection pressure,
well depth, injection pressure pulsing; and well outlet configuration. V-shaped air plumes with an apex between 40° and 60°
were obtained for all tests. The air pressure required to initiate sparging agreed closely with the sum of the air entry pressure
and the hydrostatic pressure, with higher initiation pressures required in the fine and well-graded beads. Higher air flow
rates and air saturations were obtained in coarser beads at a given pressure, and the variation in flow rate was consistent
with estimated air permeabilities. Peak average air saturations were 28–56% for the coarse-medium beads, 10% for the well-graded
beads, and 8% for the fine beads. Air saturation and the radius of influence increased modestly (<40%) as the normalized injection
pressure exceeded 0.1. Radius of influence increased by approximately a factor of two as the well depth increased, but leveled
off once the ratio of radius of influence to well depth reached 0.60–1.05. Pulsing of injection pressure had no effect on
the initiation pressure, air flow rate, or air saturation, but increased the size of the air plume and the radius of influence
slightly (<15%). Well outlet configuration had only a slight affect the radius of influence (<10%), air saturation (<10%),
or air flow rate (<12%). Dye testing showed that water surrounding the air plume circulated during continuous and pulsed sparging.
However, pulsed sparging resulted in greater and more defined circulation of water within and adjacent to the air plume, which
should reduce mass transfer limitations during sparging. 相似文献
12.
含圈闭气体的地下水流称为准饱和流,准饱和流中的圈闭气体对含水层渗透系数有重大影响。通过柱试验开展了粉砂、细砂、中砂和粗砂4种介质圈闭气体饱和度与准饱和渗透系数关系的研究。结果表明:圈闭气体饱和度明显受介质的粒径影响,在细粒介质中圈闭气体饱和度明显较大;4种介质圈闭气体饱和度在0~15%范围内,准饱和渗透系数与完全饱和相比减少了32.82%~56.38%,且准饱和渗透系数与圈闭气体饱和度之间可表达为一个负线性相关的经验公式;该公式与Faybishenko公式等效,但形式简单,参数较少,使用方便;准饱和渗透系数的变化规律可概化为圈闭气体占据了原有的有效孔隙,造成原有效孔隙度减少,从而使渗透系数减小。利用该理论,Kozeny-Carman方程能较准确地描述准饱和渗透系数的变化规律,而基于哈根-泊肃叶方程的渗透系数公式则存在较大误差,不适用于描述准饱和渗透系数;试验结果证明了室内测定饱和渗透系数时排除圈闭气体的必要性。 相似文献
13.
文章选用四氯乙烯（PCE）为代表性重非水相液体（DNAPL）,采用透射光法监测PCE在单裂隙介质中的运移过程和形态分布,探究流速及裂隙面倾斜度对PCE运移分布行为的影响。结果表明,单裂隙介质中PCE呈团块状脱离注样针,并在运移过程中呈近椭圆状。地下水流速越大,初始面积Fs越大,近椭圆的PCE离心率e越小;裂隙面倾斜度越大,初始面积Fs越小,近椭圆的PCE离心率e越小。不同流速或倾斜度条件下,入渗稳定后的PCE团块面积与离心率均明显下降。地下水流速及裂隙面倾斜度的增大对于PCE纵向运移具有促进作用,使PCE污染物前端锋面运移速率增大,在相同时间内更快运移到裂隙底部。PCE入渗停止后,流速增大促使污染源区PCE饱和度降低,使饱和度峰值随水流速度增大而减小;倾斜度增大抑制污染源区PCE饱和度降低,使饱和度峰值随倾斜度增大而增大。 相似文献
14.
为实现土的非饱和优先流迁移可视化,设计立柱装置进行非饱和渗流试验,采用透明土与数字图像处理技术,建立归一化像素强度与透明土饱和度的关系,在此基础上,通过室内模型试验,研究优先流路径连通性与相邻优先流路径旋转角对非饱和土优先流迁移的影响。试验结果表明：基于图像灰度像素强度表征非饱和透明土饱和度方法是可行的;全连通优先流（O-O型）与上连通优先流（O-C型）剖面呈现T型,中心轴剖面饱和度与边缘差异明显,下连通优先流路径（C-O型）中土体油压与基质势不足以使流体进入优先流路径形成优先流,入渗趋势与均匀流一致,O-C型优先流的稳定入渗率和湿润锋推移速度分别为C-O型的1.5倍和1.4倍;相邻O-C型优先流之间区域形成新的优先流,土体达到较高饱和度,增长速率随旋转角的增加而减小,优先流转角为90?、60?、30?时稳定入渗速率分别为均匀流的1.5、1.3、1.2倍;流体受重力影响,转角小的优先流仅沿路径一侧水平渗透,但湿润锋推移速度分别为均匀流的1.3、1.4、1.5倍,相邻优先流相互作用减弱,难以形成新的优先流。 相似文献
15.
圈闭有不连续、非流动和非混溶气体的含水层,被称为准饱和含水层。圈闭气体的存在会降低含水层的渗透性能,但准饱和渗透系数、圈闭气体饱和度和驱替速率之间的关系还没有完全被理解。本文通过室内砂性介质的驱替试验开展了圈闭气体饱和度、准饱和渗透系数和驱替速率三者相互关系的研究。研究表明,虽然总体上圈闭气体饱和度随驱替速率的增大而减小,但是在高驱替速率和低驱替速率分别出现了圈闭气体饱和度不随驱替速率变化的等值区间,该“台阶”型曲线可以采用与van Genuchten曲线类似的数学模型来表征,而砂性介质的准饱和渗透系数与圈闭气体饱和度之间呈简单的线性负相关关系。这两个经验模型说明可以用驱替速率定量估算准饱和渗透系数,该关系为利用驱替速率估算准饱和渗透系数提供了理论依据。上述准饱和水力学性质为深入理解准饱和地下水水流提供了依据。另外,驱替速率与圈闭气体饱和度的关系还表明,实验室测量完全饱和渗透系数时,应以大于初始毛细上升速率的速率进行饱和,以避免介质中的空气被水圈闭。 相似文献
16.
Air sparging (AS) is an in situ soil/groundwater remediation technology, which involves the injection of pressurized air/oxygen through an air sparging well below the zone of contamination. Characterizing the mechanisms governing movement of air through saturated porous media is critical for the design of an effective cleanup treatment system. In this research, micromechanical investigation was performed to understand the physics of air migration and subsequent spatial distribution of air at pore scale during air sparging. The void space in the porous medium was first characterized by pore network consisting of connected pore bodies and bonds. The biconical abscissa asymmetric concentric bond was used to describe the connection between two adjacent pore bodies. Then a rule‐based dynamic two‐phase flow model was developed and applied to the pore network model. A forward integration of time was performed using the Euler scheme. For each time step, the effective viscosity of the fluid was calculated based on fractions of two phases in each bond, and capillary pressures across the menisci was considered to compute the pressure field. The developed dynamic model was used to study the rate‐dependent drainage during air sparging. The effect of the capillary number and geometrical properties of the network on the dynamic flow properties of two‐phase flow including residual saturation, spatial distribution of air and water, dynamic phase transitions, and relative permeability‐capillary pressure curves were systematically investigated. Results showed that all the above information for describing the air water two‐phase flow are not intrinsic properties of the porous medium but are affected by the two‐phase flow dynamics and spatial distribution of each phase, providing new insight to air sparging. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
Naichao Feng Shiqing Cheng Haiyang Yu Wenyang Shi Xin Liu Qicheng Liu 《Arabian Journal of Geosciences》2018,11(17):519
High-pressure air injection (HPAI) is a significant enhanced oil recovery (EOR) technology of light oils especially in deep, thin, low-permeability reservoirs. The flow and heat transfer behaviors of compressed air in wellbore is essential to maximize performance of air in EOR. Due to strong compressibility of air and high injection pressure, wellbore temperature and pressure are greatly affected by friction and gas compression. However, the available models of wellbore flow and heat transfer are only accurate for thermal fluid, such as saturated steam and superheated steam, injected at relatively low pressure and high temperature. In this paper, a novel model is proposed to characterize wellbore pressure and temperature distribution for HPAI wells with consideration of dynamic behaviors of injected air. Flow and heat transfer in depth direction are coupled with air properties by iterative technique, and heat transfer in radial direction is treated as steady state in wellbore and transient state in formation. The mathematical model is solved by employing finite difference method and it is validated by field data. Then, integrated analyses of flowing pressure, heat transfer mechanism, and interaction between pressure and temperature are conducted. Results indicate that (1) as well depth increases, temperature difference between formation and air tends to become constant, and the radial heat transfer tends to reach an equilibrium state. The higher the flow rate is, the deeper the equilibrium depth is. (2) Air temperature is dominated by heat transmission from formation at low flow rates and dominated by frictional heat and gas compression effect at high flow rates. Fictional heat begins to affect air temperature at an injection rate beyond the critical value, while gas compression effect can increase air temperature in the whole calculated injection rate range. (3) Interaction between wellbore temperature and pressure is mainly achieved by altering air density. The effect of injection pressure on air temperature can be negligible, while the influence of injection temperature shows strong dependency on injection rate. 相似文献
18.
Abenezer Mekonen Prabhakar Sharma Fritjof Fagerlund 《Environmental Earth Sciences》2014,71(8):3751-3760
In this study, a series of sand packed columns were used to investigate the mobility of multiwall carbon nanotubes (MWCNTs) in unsaturated porous media under unfavorable conditions for deposition. The flow through column experiments were designed to assess water content, flow rate, and grain size effect on the mobility of MWCNTs. It was found that variation in water content had no significant effect on retention of MWCNTs until it was lowered to 16 % effective saturation. Thick water films, high flow rate, and repulsive forces between MWCNTs and porous media made MWCNTs highly mobile. Different porous media grain sizes (D 50 = 150–300 μm) were used in this study. The mobility of MWCNTs slightly decreased in finer grain sands, which was deemed to be an effect of increase in surface area and the number of depositional sites, in combination with low-pore water velocity. However, physical straining was not observed in selected fine-grain sands and aspect ratio of MWCNTs had low impact on mobility. Variations in pore-water velocity were produced by both changes in water saturation and in flow rate. At high pore-water velocities, the MWCNTs were generally mobile. However, for the combination of low-pore water velocity with either low water saturation or small grain size, some retention of MWCNTs was observed. Hence, low velocity in combination with flow through smaller pores increased MWCNT deposition. 相似文献
19.
考虑气相影响的降雨入渗过程分析研究 总被引：4，自引：1，他引：3
降雨入渗过程是水在下渗的过程中驱替空气的水-气二相流过程,对这一过程的精确模拟一直是渗流计算的难点,目前的处理方法通常是忽略孔隙气压力变化的影响。根据多相流理论,结合质量守恒定律和达西定律,建立了水-气二相流模型,模型的求解采用积分有限差分法和Newton-Raphson迭代方法,通过变换主要变量来表达相态的变化,实现了水相、气相边界条件及降雨入渗边界的精确模拟。利用上述模型对一土柱试验进行模拟,从而验证了模型的正确性,研究了一均质土层的降雨入渗过程,得到了孔隙水压力、孔隙气压力和毛细压力及含水率的变化过程。根据入渗率与地表孔隙气压力的变化关系,验证了孔隙气压力的增大对入渗水流产生阻滞作用。在求解非稳定渗流问题中,考虑空气压力变化的影响是值得研究的。 相似文献