ARCHIVED REPORTS_XR0006231 - Laserfiche WebLink

Home Browse Search

Jun 6 1996 4 20Ph1 IEG TECHNOLOGIES No 2616 P 22/34 M � . Basic System Concept As shown in Figure 1, the UV8 system consists of a specially adapted groundwater well with two separate screen sections, a groundwater treatment unit located inside the well casing (typically a "stripping reactor"), an above-ground mounted blower, and an optional off-air treatment system, The blower creates a reduced pressure within the air-tight well casing. Atmospheric air is introduced to the system, by virtue of the pressure differential, via a fresh air pipe which is open at the ground surface and connected to the stripping reactor located in the well casing Fresh air is drawn through the fresh air pipe into the stripping reactor where it is directed to a sieve plate. As air bubbles migrate upward from the sieve plate, they strip the VOCs dissolved in groundwater passing through the stripping reactor. The off-air stream, which now includes vapor-phase contaminants, is brought to the surface by the blower and treated as necessary The rapidly expanding and rising air bubbles produce an air-lift pump effect which, together with the vacuum in the well casing, elevates the groundwater in the well and causes suction at the lower well screen The subsequent fall of groundwater along the walls of the well produces an oscillating hydraulic pressure which forces the water horizontally through the upper screen into the aquifer A portion of the treated groundwater eventually migrates from the upper screen to the lower screen by means of an extensive three-dimensional groundwater flow field. in the presence of a natural groundwater flow, a portion of the flow entering the well casing will be new upstream waters which have entered through the upstream capture zone. An equal portion leaving the well 'casing will exit the circulation cell through the downstream release zone. These flows and the dimensions of the capture zone, circulation cell, and release zone can be calculated using design aids based on numerical simulations of the groundwater hydraulics. Aerobic biodegradation of organic contaminants is enhanced by the recirculation of oxygenated groundwater into the aquifer The vadose zone and capillary fringe are remediated by virtue of their exposure to the upper screened section of the UVB well by soil flushing and soil vapor extraction mechanisms Case History- Troutman—North Carolina A UVB 400 mm system (16 inch diameter well casing) was installed in September 1992 at a former retail gasoline facility in the Piedmont physiographic province in west central North Carolina A site map depicting well locations and isopleths of total BTEX concentrations prior to UVB activation appear in Figure 2 The saturated regolith consists of saprolite from a depth of about 45 feet from land surface to the top of weathered rock at about 65 feet from land surface. The saprolite is heterogeneous and vanes in grain size from medium to fine sand, to silt with clay, and is derived from the bedrock, a quartz-biotite gneiss A diagram showing the construction details of the UVB well is given as Figure 3 Depth to water at this site is 45 feet below ground surface Groundwater flow is to the south and the approximate hydraulic conductivity is 1 9 x 10-4cm/sec, A 20 foot interval of the saturated zone is being addressed by the UVB system i z 1