Resuspension of E. coli in sediment laden streams

大肠杆菌在充满沉积物的溪流中的再悬浮

• 批准号: 0967845
• 负责人: Michelle Soupir
• 金额: $ 36.5万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-01 至 2014-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0967845&HistoricalAwards=false
• 关键词: Resuspension; E.; coli; sediment; laden

Soupir, MichelleCBET-0967845The PI proposes laboratory experiments to measure resuspension of E. coli from a sediment bed and field experiments to test the resuspension relationships developed from the laboratory results. Even though previous work suggests that sediment disturbance can account for the majority of total fecal contamination, standard water quality models do not include resuspension of fecal bacteria as a source. The PI previously showed that including interactions between the sediment and the water column can improve predictions of microbial concentrations, but because most models that include resuspension of bacteria either specify a resuspension rate or calibrate as a function of only discharge, better ways to predict resuspension are needed. The main benefit of the proposed work is the ability to identify, control, and isolate the parameters affecting resuspension so that relationships to predict resuspension can be developed and tested. The objectives of the proposed work are to (1) measure the resuspension of E. coli in controlled laboratory experiments, (2) develop relationships to predict resuspension of attached and unattached E. coli as a function of properties of the flow and sediment, and (3) assess the relationships with data collected in the field. They hypothesize that (a) the resuspension rate of attached E. coli will be proportional to the resuspension rate of sediment because the attached fraction in the water column will be the same as that in the sediment bed and (b) resuspension of unattached E. coli will occur at lower shear stresses than for attached E. coli. These hypotheses are encapsulated in a physically based, quantitative framework proposed to predict resuspension. The intellectual merit of the proposed research comes from the ability to isolate and control important parameters affecting resuspension. Laboratory experiments with flow over three types of sediment will provide the first measurements of E. coli resuspension in which flow rates and sediment properties are varied systematically. Data from the laboratory experiments will be used to test and develop physically based relationships to predict resuspension of E. coli as a function of properties of the flow, sediment, and organisms. To test the formulas derived from laboratory experiments in the field, resuspension rates computed from a mass balance applied to a reach of Squaw Creek in Ames, IA will be compared to the predictions. The resulting physically based relationships will be important for reducing the parameterization of water quality models, and the laboratory experiments will provide information over a range of conditions that will help to guide the application of our results in water quality modeling. Preliminary results, as well as previous work on sediment resuspension, show that the flume experiments will be useful for studying resuspension of E. coli. The broader impacts include training a graduate student and undergraduate student; conducting outreach to schools; mentoring a new assistant professor; helping the Iowa Department of Natural Resources, which is responsible for developing total maximum daily loads, to incorporate the research results into watershed scale water quality models to develop more realistic load allocations; and collaborating with the Ames Water and Pollution Control District, which is considering adding disinfection to the wastewater treatment plant in Ames, Iowa. Careful measurements and improved models of the fate and transport of E. coli in streams will improve predictions of conditions where a risk to human health is likely and the implementation of land management practices to reduce bacterial pollution in the nation?s water bodies.

Soupir, MichelleCBET-0967845PI 提议通过实验室实验来测量沉积物床中大肠杆菌的再悬浮情况，并通过现场实验来测试从实验室结果中得出的再悬浮关系。 尽管之前的研究表明沉积物扰动可以解释粪便污染总量的大部分，但标准水质模型并不包括粪便细菌的再悬浮作为来源。 PI 之前表明，考虑沉积物和水柱之间的相互作用可以改善微生物浓度的预测，但由于大多数包含细菌再悬浮的模型要么指定再悬浮率，要么根据排放量进行校准，因此需要更好的方法来预测再悬浮。 所提出的工作的主要好处是能够识别、控制和隔离影响再悬浮的参数，以便可以开发和测试预测再悬浮的关系。拟议工作的目标是（1）在受控实验室实验中测量大肠杆菌的再悬浮，（2）建立关系以预测附着和未附着大肠杆菌的再悬浮作为流动和沉积物特性的函数，以及（3）评估与现场收集的数据的关系。 他们假设（a）附着的大肠杆菌的再悬浮率将与沉积物的再悬浮率成正比，因为水柱中的附着部分将与沉积物床中的附着部分相同，并且（b）未附着的大肠杆菌的再悬浮将在比附着的大肠杆菌更低的剪切应力下发生。 这些假设被封装在一个基于物理的定量框架中，旨在预测再悬浮。拟议研究的智力价值来自于隔离和控制影响重悬的重要参数的能力。 对三种沉积物上的流动进行的实验室实验将首次测量大肠杆菌的再悬浮，其中流速和沉积物特性会系统地变化。 实验室实验的数据将用于测试和开发基于物理的关系，以预测大肠杆菌的再悬浮作为流动、沉积物和生物体特性的函数。 为了测试现场实验室实验得出的公式，根据应用于爱荷华州艾姆斯斯阔溪河段的质量平衡计算出的再悬浮率将与预测进行比较。 由此产生的基于物理的关系对于减少水质模型的参数化非常重要，实验室实验将提供一系列条件下的信息，这将有助于指导我们的结果在水质建模中的应用。初步结果以及之前关于沉积物再悬浮的工作表明，水槽实验将有助于研究大肠杆菌的再悬浮。更广泛的影响包括培养研究生和本科生；向学校进行外展活动；指导新的助理教授；帮助负责制定最大每日总负荷的爱荷华州自然资源部将研究结果纳入流域规模水质模型，以制定更切合实际的负荷分配；并与艾姆斯水和污染控制区合作，该区正在考虑为爱荷华州艾姆斯的废水处理厂增加消毒设施。 对溪流中大肠杆菌的命运和运输进行仔细测量和改进模型将改善对可能对人类健康构成风险的情况的预测，并实施土地管理实践以减少国家水体中的细菌污染。