• ERH can generally not be used above 100
C (even though temperatures above
200
C have been observed in some cases).
• The radius of the array is limited by the soil’s electrical conductivity.
3.4.5 Free Product Thermal Enhancement Recovery: Hot
Water Flooding
Hot water flooding was first developed and used by the oil industry to increase crude
oil recovery (Burger et al. 1984; Edmondson 1965; Fournier 1965). It was then used
for polluted sites and soils remediation. Many large-scale applications have been
reported in the crude oil recovery domain (Fulton et al. 1991; USEPA 2000), yet this
technique cannot be directly applied to the field of polluted sites and soils remediation (Dokla 1981; Fournier 1965; Goodyear et al. 1996; Okasha et al. 1998). The
technique is similar to free product recovery with groundwater extraction (for
LNAPL) or waterflooding (for DNAPL) (see Chap. 2); the difference lies in the
fact that the hydraulic gradient applied to increase NAPL recovery is generated by
injecting hot water. Hot water injection reduces interfacial tension and viscosity of
the NAPL, leading to enhanced mobility (Kingston et al. 2014).
Reducing the pollutant mass also reduces discharges from the pollution source
(Falta et al. 2005a, b; Huntley and Beckett 2002; McDade et al. 2005; McGuire et al.
2006; Newell and Adamson 2005; Sale 2001; Stroo et al. 2003).
Figure 3.17 illustrates a schematic representation of hot water flooding
Field experiments have demonstrated variable NAPL recovery yields (e.g., lubricating oil and liquid coal tar) (Fulton et al. 1991; USEPA 2000). For instance, in the
case of NAPL such as phase separated lubricating oil (PSLO), it was demonstrated
that hot water injection recovered the NAPL more easily compared to non-heated
water (Fulton et al. 1991). The PSLO dynamic viscosities were 926, 140, and
67 Saybolt Universal Seconds (SUS), respectively, for temperatures of 4, 50, and
99
C.
A free product pumping system was installed via a series of 13 recovery/recharge
trenches without thermal enhancement. The recovery kinetics were 2.32 liter per
month (Lpmo) per linear meter of recovery trench (over an 18-month period).
Next, pilot studies with hot water flooding over a 42-day period produced
recovery kinetics of 16.15 Lpmo/linear meter of recovery trench. Subsequent fullscale experiments significantly increased the DNAPL recovery kinetics: the volume
recovered with pumping without thermal enhancement was 16.82 m
3 in 48 months
(i.e., 0.35 m
3
Ámo
À1 ), whereas thermal enhancement yielded 45.27 m
3 in 30 months
(i.e., 1.51 m
3 Ámo
À1 ). The temperatures reached were 47–63
C in the trenches and
25–50
C between trenches.
Field studies on hot water flooding applied to LNAPL, such as lubricating oil,
were not conclusive due to insufficient data (USEPA 2000).
188
S. Colombano et al.
C (even though temperatures above
200
C have been observed in some cases).
• The radius of the array is limited by the soil’s electrical conductivity.
3.4.5 Free Product Thermal Enhancement Recovery: Hot
Water Flooding
Hot water flooding was first developed and used by the oil industry to increase crude
oil recovery (Burger et al. 1984; Edmondson 1965; Fournier 1965). It was then used
for polluted sites and soils remediation. Many large-scale applications have been
reported in the crude oil recovery domain (Fulton et al. 1991; USEPA 2000), yet this
technique cannot be directly applied to the field of polluted sites and soils remediation (Dokla 1981; Fournier 1965; Goodyear et al. 1996; Okasha et al. 1998). The
technique is similar to free product recovery with groundwater extraction (for
LNAPL) or waterflooding (for DNAPL) (see Chap. 2); the difference lies in the
fact that the hydraulic gradient applied to increase NAPL recovery is generated by
injecting hot water. Hot water injection reduces interfacial tension and viscosity of
the NAPL, leading to enhanced mobility (Kingston et al. 2014).
Reducing the pollutant mass also reduces discharges from the pollution source
(Falta et al. 2005a, b; Huntley and Beckett 2002; McDade et al. 2005; McGuire et al.
2006; Newell and Adamson 2005; Sale 2001; Stroo et al. 2003).
Figure 3.17 illustrates a schematic representation of hot water flooding
Field experiments have demonstrated variable NAPL recovery yields (e.g., lubricating oil and liquid coal tar) (Fulton et al. 1991; USEPA 2000). For instance, in the
case of NAPL such as phase separated lubricating oil (PSLO), it was demonstrated
that hot water injection recovered the NAPL more easily compared to non-heated
water (Fulton et al. 1991). The PSLO dynamic viscosities were 926, 140, and
67 Saybolt Universal Seconds (SUS), respectively, for temperatures of 4, 50, and
99
C.
A free product pumping system was installed via a series of 13 recovery/recharge
trenches without thermal enhancement. The recovery kinetics were 2.32 liter per
month (Lpmo) per linear meter of recovery trench (over an 18-month period).
Next, pilot studies with hot water flooding over a 42-day period produced
recovery kinetics of 16.15 Lpmo/linear meter of recovery trench. Subsequent fullscale experiments significantly increased the DNAPL recovery kinetics: the volume
recovered with pumping without thermal enhancement was 16.82 m
3 in 48 months
(i.e., 0.35 m
3
Ámo
À1 ), whereas thermal enhancement yielded 45.27 m
3 in 30 months
(i.e., 1.51 m
3 Ámo
À1 ). The temperatures reached were 47–63
C in the trenches and
25–50
C between trenches.
Field studies on hot water flooding applied to LNAPL, such as lubricating oil,
were not conclusive due to insufficient data (USEPA 2000).
188
S. Colombano et al.