Kouli_etal_2008_Groundwater modelling_BOOK.pdf - Pantelis ...

A Modeling Approach Supporting Air Sparging System Design 81
removing pollutants is the Zone Of Treatment (ZOT SVE ), where ΔP g exceeds 25 Pa (Dixon et
al., 2006) or, alternatively, air velocity is higher than 1.0 10 -4 m s -1 (USACE, 2002).
Pilot Plant
An AS+SVE pilot plant (Fig. 1) is usually composed by:
• one injection well (P AS ) and one extraction well (P SVE ), equipped with monitoring
and control devices at the well head (pressure gauge, air flow meter, pressure relief
valve, and flow control valve). Vertical wells are usually used, 25 mm to 100 mm in
diameter; treatment effectiveness does not seem significantly affected by well
diameter, but high frictional losses can result in small deep wells. Screen length of
P AS ranges between 0.3 m and 0.7 m, because air often escapes within a very short
interval near the top of longer well screens; the top of the screen is located at about
1.5 m below pollution (USACE, 2008; USEPA, 2004);
• an air compressor or a blower connected to P AS , and a blower or a vacuum pump
connected to P SVE ;
• 3 to 9 monitoring wells for groundwater and the vadose zone, located in various
directions (to assess soil heterogeneities) and at various distances from P AS and P SVE ,
according to the expected ZOI AS and ZOI SVE . Monitoring wells for groundwater are
equipped for the measurement of the piezometric level, whereas the air pressure is
measured in the vadose zone.
Figure 1. AS + SVE pilot plant.