The Effect of Fractures on the Reclamation ofNAPL
75
concentration of equilibrium, e;. The effect of the surfactant additive on the
coefficient of interphase mass transfer, kfi is somehow more complicated and
subject to various effects originating from properties of the porous medium, rate
of flushing, flushing interruptions, etc. However, the study of Rubin et al. (2000)
has indicated that under constant and identical flow rates through sand columns
kerosene flushing with pure water and surfactant enhancement showed almost
identical k f values. In the present study we apply this result and consider that the
surfactant only increases the e; value. In the framework of using the
dimensionless parameters of the present study, this effect is represented by the
change of the value of Cnv. We may introduce the parameter of comparative
surfactant effect:
N = e nv
SE
e '
nvO
(35)
where CvO is the value of Cnv with no surfactant additive.
Simulations of the complete aquifer reclamation with different values of NSE,
NM and KjO provide information about the quantitative increase of the reclamation
efficiency by the surfactant additive. Using a range of values of NSE• based on
field and laboratory studies (e.g., Sabatini et al. 1998; Rubin et al. 2000), results
shown in Fig. 9 suggest that the use of surfactants can decrease the volume of
treated water, as well as the total reclamation time. The order of magnitude of
these effects is nearly identical in cases of low and high values of KjO, however,
the absolute value of the changes is substantially larger for small values of KjO.
Surfactant flushing, therefore, appears to be most appropriate when KjO is small.
However, increasing NSE beyond the value 6 does not decrease significantly the
reclamation time and the treated water volume. Surfactant additions should be
considered in the development of an optimal pump-and-treat arrangement.
However, cost calculation in this case should incorporate the cost of surfactant
supply and its possible recovery.
75
concentration of equilibrium, e;. The effect of the surfactant additive on the
coefficient of interphase mass transfer, kfi is somehow more complicated and
subject to various effects originating from properties of the porous medium, rate
of flushing, flushing interruptions, etc. However, the study of Rubin et al. (2000)
has indicated that under constant and identical flow rates through sand columns
kerosene flushing with pure water and surfactant enhancement showed almost
identical k f values. In the present study we apply this result and consider that the
surfactant only increases the e; value. In the framework of using the
dimensionless parameters of the present study, this effect is represented by the
change of the value of Cnv. We may introduce the parameter of comparative
surfactant effect:
N = e nv
SE
e '
nvO
(35)
where CvO is the value of Cnv with no surfactant additive.
Simulations of the complete aquifer reclamation with different values of NSE,
NM and KjO provide information about the quantitative increase of the reclamation
efficiency by the surfactant additive. Using a range of values of NSE• based on
field and laboratory studies (e.g., Sabatini et al. 1998; Rubin et al. 2000), results
shown in Fig. 9 suggest that the use of surfactants can decrease the volume of
treated water, as well as the total reclamation time. The order of magnitude of
these effects is nearly identical in cases of low and high values of KjO, however,
the absolute value of the changes is substantially larger for small values of KjO.
Surfactant flushing, therefore, appears to be most appropriate when KjO is small.
However, increasing NSE beyond the value 6 does not decrease significantly the
reclamation time and the treated water volume. Surfactant additions should be
considered in the development of an optimal pump-and-treat arrangement.
However, cost calculation in this case should incorporate the cost of surfactant
supply and its possible recovery.