Groundwater, upflow

River water results mainly from two contributions surface runoff of falling rainwater and groundwater upflow. Surface overland runoff is the consequence of precipitation on saturated or impervious surfaces its behavior is cyclical because it depends on the wet and dry spells on Earth. 

Upconing, whereby saline water that is underlying fresh groundwater upflows at a rate sufficiently high so as to cause the salt water to be drawn into the aquifer well in an upward-shaped cone. About two-thirds of the United States freshwater aquifers could become contaminated by underlying saline water. 

In a typical countercurrent moving-bed carbon column employing upflow of the water, two or more columns are usually provided and are operated in series. The influent contaminated groundwater enters the bottom of the first column by means of a manifold system that uniformly distributes the flow across the bottom. The groundwater flows upward through the column. The unit hydraulic flow rate is usually 2 to 10 gpm/ft2. The effluent is collected by a screen and manifold system at the top of the column and flows to the bottom manifold of the second column. The carbon flow is not continuous, but instead is pulsed. 

Katsoyiannis, I., Zouboulis, A., Althoff, H. and Bartel, H. (2002) As(III) removal from groundwaters using fixed-bed upflow bioreactors. Chemosphere, 47(3), 325-32. 

The Livermore study used a 1.8 L upflow reactor, packed with a 1% w/w Pd/alumina catalyst, nominally 0.32 cm in diameter. (McNab and Ruiz 1998) The water supply consisted of groundwater from a well at the Livermore site and contained PCE (5-7 jig/L), TCE (500-600 tig/L), 1,1-DCE (15-25 pg/L), CT (8-15 fig/L), CF (4-10 gg/L), and 1,2-DCA (4-10 jrg/L). The water was first passed through an electrolyzer, which served as a source of hydrogen. With an average residence time of 2.3 minutes, the column showed >95% removal of chlorinated ethylenes (PCE, TCE and 1,1,-DCE) and CT. The apparent first order rate constants for all four compounds were approximately 72/hour. Chloroform was removed at a much slower rate (<32/hour) and 1,2-DCA removal was not significant. These results are also consistent with the batch studies of Lowry which showed rapid reaction of... 

Answer 18.3 At the groundwater downflow direction. Why not at the upflow direction ... 

Upflow fixed bed reactors or submerged biofilters (SBF) have upward groundwater flow, the packing material is submerged under water and no bed expansion is obtained [45,94-97]. 

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