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The impact of column orientation on the transport of C. parvum-sized microspheres was investigated by operating flow-through columns packed with sieved aquifer material in vertical and horizontal orientations. Breakthrough of microspheres in the vertical columns occurred after ~1.7 pore volumes, after which microsphere concentrations ranged from 182 to 556 microspheres/L (~4.6 to 5.1 log removal). In columns operated in the horizontal orientation, microsphere concentrations after ~2.9 pore volumes ranged from 1100 - 1200 micropheres/L (~4.3 to 4.4 log removal). Unfortunately, complete breakthrough of microspheres may not have occurred during the experiments. The preliminary results of this study suggest that slightly higher removals of C. parvum-sized microspheres may be possible in columns operated in a vertical position. This result is consistent with the hypothesis that laboratory investigations of colloidal filtration and transport in the subsurface should be conducted with columns in a more horizontal orientation because vertical columns may enchance the removal of microorganisms by sedimentation. It is also possible that factros such as the formation of preferential flow paths along the top of the soil in the horizontal columns (resulting from media settling) and analytical may complicate these results. Includes 16 references, figures.

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Edition: Vol. - No. Published: 11/01/2002 Number of Pages: 9File Size: 1 file , 270 KB