Kouli_etal_2008_Groundwater modelling_BOOK.pdf - Pantelis ...

A Modeling Approach Supporting Air Sparging System Design 105
Number and location of AS or SVE wells
Simulations were performed to assess the proper number and location of AS and SVE
wells in order to entirely cover the polluted zone in soil by the injected air. Plants with two,
three or four injection wells were modeled, each one screened -22 m to -22.7 m g.s. and
operating at Q V,AS,pil . The optimal solution, composed by four injection wells placed 4.5 m
from the others, is reported in Fig. 17, where the ZOI AS at stationary conditions over
horizontal sections parallel to the XY plane at different depths [e.g.: at the bottom of pollution
in soil, that is -23 m g.s., in Fig. 17(b); at the middle of the active zone of the screen of
injection wells, that is -22.35 m g.s., in Fig. 17(c); at half depth between water table under
natural conditions and the top of the screen of the injection wells, that is -18.5 m g.s., in Fig.
17(d); at water table under natural conditions, that is -15 m g.s., in Fig. 17(e)] are shown .
Asymmetry in the pictures is due to the grid, whose number of elements is limited by
PetraSym.
Fig. 18 compares air saturation obtained for plant configurations where four wells are
place at a distance of 2 m [Fig. 18(a)] and 4.5 m [Fig. 18(b)]. In the upper part of the figure,
sections parallel to the XZ plane passing through the baricentric position of the AS injection
system are shown, whereas in the lower part, sections parallel to the XY plane at -18.5 m g.s.
are shown [plane γ in Fig. 17(a)]. Where a reduced distance among wells is applied, values of
S g ≥ 0.1 can be obtained within the red circle but air saturation is low over a large part of the
polluted soil. With a longer distance among wells, S g ≥ 0.05 within the orange circle, wider
than in Fig. 18(a).
Figure 18. Air saturation S g at stationary conditions for an injection system composed by four wells, 2
m far (a) or 4.5 m far (b). In the upper part, plane α is parallel to the XZ plane (passing through the
baricentric position of the AS injection system). In the lower part, plane β is parallel to the XY plane at
-18.5 m g.s.; red and orange circles enclose zones where S g ≥ 0.1 and S g ≥ 0.05 respectively. The dashed
brown line delimits pollution in soil.