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Browsing by Author "Robinson, Michael A."

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    A finite element model of submarine ground water discharge to tidal estuarine waters
    Robinson, Michael A. (Virginia Tech, 1996)
    In the research presented here, a new ground water model, FEMCoast, was developed to simulate ground water discharge to the intertidal zone of estuarine systems. This research may be the first attempt to model the ground water discharge process in a tidal estaurine system. The development of FEM Coast was undertaken as no existing ground model was capable of directly simulating the dynamic boundary conditions along the sediment water interface of the intertidal zone. Reproducing the dynamic tidal boundary conditions along the sediment water interface was determined to be essential to replicating the complex salinity gradients observed in the ground water within the intertidal zone. Field data and model results confirmed the presence of a region of ground water where an inverted salinity gradient existed. In this region the concentration of salinity decreased with depth from the ground surface. FEMCoast was also able to reproduce field data on the movement of the near shore water table and ground water discharge rates and patterns. However, the model was not able to replicate the short-term fluctuation in the concentration of salinity within the aquifer due to changes in the concentration of salinity within Cherrystone Inlet. It is believed that the inability to account for the wave action of the tides within the intertidal zone is responsible for this difficulty. The use of FEMCoast integrated with field studies provided a new method to investigate ground water discharge to tidal estuarine systems.
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    Removal of organic contaminants from groundwater by reverse osmosis
    Robinson, Michael A. (Virginia Tech, 1990)
    The performance of a poly(ether/urea) membrane has been evaluated in a full scale reverse osmosis system. A series of experiments were conducted with six aromatic compounds - anthracene, pyrene, fluorene, 2-chlorobiphenyl, 2,4,6 trichlorophenol, and pentachlorophenol- and four volatile compounds - trichloromethane, bromodichloromethane, dibromochloromethane, and trichloroethene - as single and multi-solute contaminants. The objectives of the experiments were to determine if poly(ether/urea) membranes could produce a permeate that met maximum contaminant levels (MCL) set by the Safe Drinking Water Act (SDWA) and to correlate membrane performance with physical/chemical properties of the solute contaminants. Aromatic contaminants were removed to concentrations below the current MCLs. However, volatile contaminants were not sufficiently rejected by the membrane to meet either the MCL for total trihalomethanes or trichloroethene. Sorption onto the poly(ether/urea) was found to occur for several of the aromatic compounds tested in this research. This prevented developing any relationship between membrane performance and physical/chemical properties of the solute.