Integrated modeling and experimental evaluation of hydrodynamic and microbial controls on DNAPL dissolution and detoxification

DNAPL 溶解和解毒的流体动力学和微生物控制的集成建模和实验评估

• 批准号: 0934004
• 负责人: Jennifer Becker
• 金额: $ 37.62万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0934004&HistoricalAwards=false
• 关键词: Integrated; modeling; experimental; evaluation; hydrodynamic

0934004BeckerIn situ bioremediation based on biological reductive dehalogenation is now an established remediation approach for sites contaminated with aqueous-phase chlorinated ethenes. However, the EPA estimates that chlorinated ethenes are present as dense non-aqueous phase liquids (DNAPLs) at 46,000 contaminated sites in the U.S. The presence of DNAPL forms of these contaminants, which are known or suspected carcinogens, is a major obstacle to remediation efforts that has widespread implications for human and ecological health. Importantly, abiotic dissolution of DNAPLs into groundwater is a slow process and may require several hundred years to deplete the DNAPL source of contamination. Several in situ DNAPL treatment methods use physicochemical processes to mobilize and subsequently capture and/or destroy contaminants and thus accelerate the clean-up process. These methods can be difficult and costly to implement and may preclude bioremediation of dissolved contaminants by making conditions inhospitable to microorganisms.Recently, interest has grown in the use dehalorespiring bacteria to treat DNAPLs through bioenhanced dissolution, i.e., enhanced mass removal from chlorinated ethene DNAPLs through reductive dechlorination of dissolved contaminants near the DNAPL-water interface. This approach is appealing because it does not rely on DNAPL mobilization and is compatible with the clean-up of dissolved contaminants using bioremediation. Although bioenhanced dissolution appears promising, the design of biological DNAPL source treatment measures using a "black box" approach may not promote and sustain the growth of the populations with the greatest potential to bioenhance dissolution rates. The proposed project focuses on understanding the interrelated roles that hydrodynamics and competition among different dehalorespiring populations, as well as other community members, play in determining the distribution of dehalorespiring populations in the DNAPL source zone and dissolved contaminant plume and the resulting impact on the magnitude of bioenhanced dissolution and the extent of detoxification. Evaluation of the hydrodynamic and microbial controls on bioenhanced dissolution and detoxification of chlorinated ethenes will be accomplished using an integrated modeling and experimental approach that includes the following key objectives: (1) Mathematical modeling will be used to theoretically predict the relationships between microbial competition, hydrodynamic conditions, and bioenhancement for three model scenarios and design a micromodel system for studying DNAPL dissolution and source-zone microbial ecology at the porescale.(2) The micromodels will be used to independently estimate key system parameters and test model predictions for the three scenarios by experimentally evaluating the effects of microbial competition and hydrodynamics on population distribution, dissolution bioenhancement and plume detoxification. An innovative fluorescent in situ hybridization approach will be used to directly visualize and quantify population distribution in the micromodel. (4) An intermediate-scale flow cell will be used to test whether the micromodel experiments and mathematical modeling can predict bioenhancement effects in a scaled up system. (5) Mathematical modeling will be refined based on the experimental results and used to predict the effects of microbial competition and hydrodynamics on DNAPL source zone longevities for four DNAPL configurations.The proposed research will advance our understanding of how hydrodynamic conditions and other factors influence the distribution and outcome of competition among dehalorespiring and other populations for growth substrates in environments containing DNAPL and dissolved contaminants. This information will transform how we interpret the biological and physical phenomena affecting contaminant behavior at the many sites containing DNAPL source zones and how we direct our remediation efforts at those sites. Most importantly, it will be used to determine the conditions under which biological source zone treatment is appropriate and design treatment systems that optimize bioenhancement of DNAPL dissolution and the realization of site clean-up goals.Participation of underrepresented groups in science and engineering disciplines will be promoted through research experiences that partner community college (CC) students at a Minority Serving Institution with undergraduate students at the University of Maryland and provide training opportunities for CC faculty. The development of a short course offered through a major bioremediation conference, as well as an interactive Web-based simulation tool, will ensure results are broadly disseminated and applied and promote lifelong learning among bioremediation practitioners.

基于生物还原脱卤化的原位生物修复是目前公认的对水相氯代乙烯污染场地的修复方法。然而，美国环保署估计，在美国46,000个污染地点，氯化乙烯以稠密非水相液体(DNAPL)的形式存在。这些污染物的DNAPL形式的存在是已知或疑似致癌物质，是对人类和生态健康具有广泛影响的补救工作的主要障碍。重要的是，DNAPL在地下水中的非生物溶解是一个缓慢的过程，可能需要数百年才能耗尽DNAPL污染源。几种就地处理DNAPL的方法使用物理化学过程来动员并随后捕获和/或销毁污染物，从而加快清理进程。这些方法实施起来既困难又昂贵，而且可能会使微生物不适宜的条件阻碍对溶解污染物的生物修复。最近，人们对使用脱卤菌通过生物强化溶解来治疗DNAPL产生了兴趣，即通过还原脱氯DNAPL-水界面附近的溶解污染物来增强从氯化乙烯DNAPL中的质量去除。这种方法很有吸引力，因为它不依赖于DNAPL动员，并且与使用生物修复清除溶解的污染物兼容。尽管生物强化溶解看来很有希望，但使用“黑箱”方法设计生物DNAPL源处理措施可能不会促进和维持具有最大潜力生物强化溶解速率的种群的增长。拟议的项目侧重于了解不同脱卤性呼吸种群以及其他社区成员之间的水动力学和竞争在决定DNAPL源区脱卤性呼吸种群和溶解污染物羽流的分布以及由此对生物强化溶解的程度和解毒程度的影响方面所起的相互关联的作用。对水动力和微生物控制对氯代乙烯生物强化溶解和解毒的评价将通过模拟和实验相结合的方法来完成，该方法包括以下主要目标：(1)将使用数学模型从理论上预测三种模型情景下微生物竞争、水动力条件和生物强化之间的关系，并设计一个微型模型系统来研究DNAPL在初始阶段的溶解和源区微生物生态。(2)通过实验评估微生物竞争和水动力学对种群分布、溶解生物增强和羽流解毒的影响，这些微观模型将用于独立地估计关键系统参数并检验模型预测。一种创新的荧光原位杂交方法将被用于直接可视化和量化微观模型中的种群分布。(4)将使用一个中等规模的流动池来测试微观模型实验和数学模型是否能够预测放大系统中的生物强化效果。(5)将根据实验结果建立数学模型，并用于预测微生物竞争和水动力学对DNAPL四种构型DNAPL源区寿命的影响。该研究将加深我们对水动力条件和其他因素如何影响DNAPL和溶解污染物环境中脱盐呼吸和其他种群之间竞争的分布和结果的理解。这些信息将改变我们如何解释影响DNAPL污染源区域的许多地点的污染物行为的生物和物理现象，以及我们如何指导我们在这些地点的补救工作。最重要的是，它将被用来确定合适的生物源区域处理条件，并设计优化生物促进DNAPL溶解和实现场地清理目标的处理系统。将通过将少数族裔服务机构的社区学院(CC)学生与马里兰大学的本科生合作的研究经验，促进未被充分代表的群体参与科学和工程学科，并为CC教师提供培训机会。通过一次重要的生物修复会议开发一个短期课程以及一个基于网络的互动模拟工具，将确保成果得到广泛传播和应用，并促进生物修复从业者的终身学习。