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' tict 10 1996 r I"PM IEG TECHNOLOGIES No 39"A P 40!54 <br /> technology which will be listed. <br /> IN SITU REMEDIATION OF VOLATILE CONTAMINANTS BY THE UVB METHOD <br /> The UVB helps to remove volatile substances from the oundwater, the <br /> P gr , <br /> unsaturated zone, and the capillary fringe When using the UVB method, a special well <br /> with two screen sections is employed, one at the aquifer bottom and one at the <br /> groundwater surface (Fig. 1) or below an aquitard in a confined aquifer The borehole <br /> reach between the two screen sections should be made impermeable. One well should <br /> be used to remediate only one aquifer (phreatic or confined) and should not connect <br /> different aquifers. <br /> fresh air Cctivated carbon <br /> ventilator filler <br /> Used au <br /> --Kr <br /> cleaned air <br /> soil air removed <br /> /v1a suction <br /> � stripping Zone <br /> /working water level <br /> . 1 <br /> air rntrGduCion <br /> 4JP2 a* <br /> ter+ <br /> resting water levet <br /> -; " • ocditioncl pump to <br /> sucoart the crr bubble <br /> etf ec• <br /> _ seporanon plate <br /> extensive ygreundwater <br /> ~' c,rcJtatMn <br /> bonznale lilting <br /> .__... <br /> r- <br /> ^- filter;rcvv sealing rmterlcl <br />' t •aquifer bottom <br /> Figure 1: Vacuum vaporizer well (UVB)-with additional pump and separating plate. <br /> I <br /> The upper, closed part of the well is maintained at below atmospheric pressure <br />' by a ventilator. This lifts the water level within the well casing. The fresh air for the <br /> upper part of the well casing is introduced through a fresh air pipe: the upper end is <br /> open to the atmosphere, and the lower end terminates in a pinhole plate. The height of <br /> the pinhole plate is adjusted such that the water pressure is lower there than the <br /> atmospheric pressure. Therefore, the fresh air is drawn into the system. The reach <br /> between the pinhole plate and the water surface in the well casing is the stripping zone, <br /> in which an air bubble flow develops. The rising air bubbles produce a pump effect, <br /> which moves the water up and causes a suction effect at the well bottom. In recent wells, <br /> a separating plate and an additional pump (Fig 1) are used to reinforce the pumping <br /> effect of the air bubbles. Additionally, soil air is drawn from the surrounding <br />