. f : thickness of freshwater zone above sea level (m)
ρ f : freshwater density (kg m
À3 )
ρ s : saltwater density (kg m
À3 )
2.4.2 Waterflooding
Waterflooding, or hydraulic displacement, or dual-phase extraction take into account
the fact that, under certain conditions, hydraulic gradients can cause the DNAPL
pool to migrate (Craig 1971; Willhite 1986; Gerhard et al. 2001; Alexandra et al.
2012).
The process comprises specific oleophilic skimmers, and dedicated water pumps
allocated to groundwater pumping (just above the DNAPL/water interface). These
are placed either in the same recovery well or in two separate wells (Fig. 2.18).
Two methods are implemented to obtain a first estimate of the necessary pumping
characteristics.
1. A DNAPL pool located on an impermeable substratum has the following characteristics: (a) capillary pressure increases with the pool’s internal depth;
(b) capillary pressures are identical at the edges of the pool. When a hydraulic
gradient is applied everywhere in the pool, the capillary pressures are higher in
the downstream zone than in the upstream zone of the pool. These differences can
cause the DNAPL pool to migrate. According to Kueper and Gerhard (2014), the
Fig. 2.17 Schematic representation of free product recovery by groundwater extraction and
skimming (upwelling) [adapted from Villaume et al. (1983)]
90
S. Colombano et al.
ρ f : freshwater density (kg m
À3 )
ρ s : saltwater density (kg m
À3 )
2.4.2 Waterflooding
Waterflooding, or hydraulic displacement, or dual-phase extraction take into account
the fact that, under certain conditions, hydraulic gradients can cause the DNAPL
pool to migrate (Craig 1971; Willhite 1986; Gerhard et al. 2001; Alexandra et al.
2012).
The process comprises specific oleophilic skimmers, and dedicated water pumps
allocated to groundwater pumping (just above the DNAPL/water interface). These
are placed either in the same recovery well or in two separate wells (Fig. 2.18).
Two methods are implemented to obtain a first estimate of the necessary pumping
characteristics.
1. A DNAPL pool located on an impermeable substratum has the following characteristics: (a) capillary pressure increases with the pool’s internal depth;
(b) capillary pressures are identical at the edges of the pool. When a hydraulic
gradient is applied everywhere in the pool, the capillary pressures are higher in
the downstream zone than in the upstream zone of the pool. These differences can
cause the DNAPL pool to migrate. According to Kueper and Gerhard (2014), the
Fig. 2.17 Schematic representation of free product recovery by groundwater extraction and
skimming (upwelling) [adapted from Villaume et al. (1983)]
90
S. Colombano et al.