Resuspension of E. coli in sediment laden streams

建议进行实验室实验，以测量沉积物床中的大肠杆菌的再悬浮，并建议进行实地实验，以测试根据实验室结果建立的再悬浮关系。尽管以前的工作表明，沉积物干扰可能占总粪便污染的大部分，但标准水质模型没有将粪便细菌的再悬浮作为来源。PI先前表明，包括沉积物和水柱之间的相互作用可以提高对微生物浓度的预测，但由于大多数包括细菌再悬浮的模型要么指定再悬浮速率，要么作为仅排放的函数进行校准，因此需要更好的方法来预测再悬浮。拟议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，以便能够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)建立预测附着和未附着的大肠杆菌作为水流和沉积物特性函数的再悬浮的关系，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速率将与沉积物的再悬浮速率成正比，因为水柱中的附着部分将与沉积物床中的附着部分相同，以及(B)未附着的大肠杆菌的再悬浮发生在比附着的大肠杆菌更低的剪应力下。这些假设被封装在一个基于物理的、定量的框架中，以预测再悬浮。拟议研究的智力价值来自于分离和控制影响再悬浮的重要参数的能力。在三种类型的沉积物上流动的实验室实验将提供第一批对大肠杆菌再悬浮的测量，其中流速和沉积物特性是系统地变化的。实验室实验的数据将被用来测试和发展基于物理的关系，以预测作为水流、沉积物和生物体特性的函数的大肠杆菌的再悬浮。为了验证从野外实验室实验中得出的公式，根据质量平衡计算的再悬浮率将应用于亚利桑那州艾姆斯的Squaw Creek河段，并与预测进行比较。由此产生的基于物理的关系对于减少水质模型的参数化将是重要的，实验室实验将提供一系列条件的信息，这将有助于指导我们的结果在水质建模中的应用。初步结果和前人关于底泥再悬浮的工作表明，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训一名研究生和本科生；对学校进行外联；指导一名新的助理教授；帮助负责制定最大日总负荷的爱荷华州自然资源部将研究结果纳入分水岭规模的水质模型，以制定更现实的负荷分配；以及与艾姆斯水和污染控制区合作，后者正在考虑为爱荷华州艾姆斯的废水处理厂增加消毒。仔细测量和改进溪流中大肠杆菌的去向和运输模型，将提高对可能对人类健康构成威胁的条件的预测，并改进土地管理措施的实施，以减少国家--S--水体的细菌污染。

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.