HR: 0800h
AN: H31B-1296    [Abstracts]
TI: Analysis of a Multi-Well Tracer Test at a Bank Filtration Site in an Arid Environment of El Paso, Texas
AU: * Abdel-Fattah, A N
EM: anabdel-fattah@ag.tamu.edu
AF: Texas A&M University, 1380 A&M Circle, El Paso, TX 79927
AU: Langford, R
EM: langford@geo.utep.edu
AF: The University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968
AU: Schulze-Makuch, D
EM: dirksm@wsu.edu
AF: Washington State University, Webster Physical Science Bldg, P.O. Box 642812 , Pullman, WA 99164
AU: Sheng, Z
EM: z-sheng@tamu.edu
AF: Texas A&M University, 1380 A&M Circle, El Paso, TX 79927
AB: River bank filtered water is an important component of the drinking water production in many areas of the world. In riverbank filtration, the removal of pathogens is an important task for the production of good quality drinking water. The hydrogeological factors and spatial changes in the water's microbiology during the transport from the river to the aquifer have important implications on the quality of the produced water. The goal of this study was to investigate riverbank infiltration effectiveness in arid environments such as that of El Paso, Texas. The hydrostratigraphic units and hydrogeologic conditions were characterized with lithologic samples obtained from all boreholes collected during the construction of twelve observation wells and one production well in the site, which were constructed near the artificial stream to provide geologic and hydrologic information. The shallow aquifer is composed of three unites: high hydraulic conductivity layers on the top and bottom, and low conductivity layer in the middle. In this study advective transport of microspheres was compared with a conservative tracer such as bromide. Bromide was injected into an observation well at the channel margin. Simultaneously, 1, 6 and 10 micron-diameter fluorescent microspheres equivalent to Giardia, Cryptosporidium, and bacteria sizes were injected into the stream bottom and two observation wells to assess the suitability of microspheres as abiotic analogs in future investigations involving the physical aspects of bacteria and protozoa transport behavior. The 17.8 day-tracer test provided valuable results that are relevant to the transport of pathogens through the subsurface under riverbank filtration conditions. The 1 micron-size microspheres were abundant in the pumping and observation wells and showed multiple peaks similar to the bromide results. Microspheres from the three injection sites had distinctly different transport paths and rates. The 6 and 10 micron-size microspheres were observed in low to almost zero concentrations. The very low detection of larger sized microspheres indicates a potential attenuation of Cryptosporidium and Giardia-size microspheres under riverbank filtration conditions.
DE: 1838 Infiltration
DE: 4808 Chemical tracers
SC: Hydrology [H]
MN: Fall Meeting 2005