TY - JOUR

T1 - An experimental investigation of NAPL pool dissolution enhancement by flushing

AU - Seagren, Eric A.

AU - Rittmann, Bruce E.

AU - Valocchi, Albert J.

N1 - Funding Information:
The research described in this article was supported by grant DE-FG-02-89ER60773 from the Subsurface Science Program of the Office of Health and Environmental Research, US Department of Energy (DOE). This paper has not been subjected to the DOE's peer or administrative review and, therefore, does not necessarily reflect the views of the department and no official endorsement should be inferred. Part of this paper was presented at the 67th Annual Conference and Exposition, WEFTEC '94, of the Water Environment Federation, Chicago, IL, USA, Oct. 15–19, 1994. The authors thank Cassandra Vaughn for her laboratory assistance.

PY - 1999/4

Y1 - 1999/4

N2 - Experiments coupled with mathematical modeling are used to further elucidate the quantification of NAPL pool dissolution and its enhancement by water flushing. The experiments were performed using glass bead-packed column reactors with small pools of neat toluene or a toluene in dodecane mixture (toluene mole fraction, X(tol)~0.02 or 0.09). Experimental quasi-steady-state toluene dissolution fluxes were determined by a mass-balance approach. The results of these experiments are used to quantify the impact of flushing on the NAPL pool dissolution flux, J, for wide ranges of two of the key controlling parameters-equilibrium concentration, C(S), and average pore water velocity, v(x). In addition, the experimental dissolution flux data are used to evaluate predictions made using independently obtained model parameters and analytical mathematical models incorporating the two basic approaches used for mathematically describing the interphase distribution of NAPLs: the local equilibrium (LE) approach; and the mass transfer limited, or nonequilibrium (NE) approach. The data from the experiments with a neat toluene pool demonstrate the expected trend of increasing J as v(x) increased from approximately 2 to 30 m/day. The LE model and the NE model with an average mass transfer coefficient, k(l)=4.76 m/day, were able to describe the neat toluene pool data for v(x)<18 m/day reasonably well. However, for v(x)>18 m/day, the NE model with k(l)=4.76 m/day provides a better description of the data, suggesting that the equilibrium boundary condition may become invalid for very high velocities. The experiments with the binary toluene in dodecane pools also show the expected trend of increasing J with increasing v(x). The LE model describes the binary pool data reasonably well for the entire range of v(x) studied (approximately 0.1 to 10 m/day), and the NE model predictions with the average k(l)=4.76 m/day determined in the neat-pool studies do not deviate significantly from the LE model in this v(x) range, although small deviations occur for >10 m/day. Copyright (C) 1999 Elsevier Science B.V.

AB - Experiments coupled with mathematical modeling are used to further elucidate the quantification of NAPL pool dissolution and its enhancement by water flushing. The experiments were performed using glass bead-packed column reactors with small pools of neat toluene or a toluene in dodecane mixture (toluene mole fraction, X(tol)~0.02 or 0.09). Experimental quasi-steady-state toluene dissolution fluxes were determined by a mass-balance approach. The results of these experiments are used to quantify the impact of flushing on the NAPL pool dissolution flux, J, for wide ranges of two of the key controlling parameters-equilibrium concentration, C(S), and average pore water velocity, v(x). In addition, the experimental dissolution flux data are used to evaluate predictions made using independently obtained model parameters and analytical mathematical models incorporating the two basic approaches used for mathematically describing the interphase distribution of NAPLs: the local equilibrium (LE) approach; and the mass transfer limited, or nonequilibrium (NE) approach. The data from the experiments with a neat toluene pool demonstrate the expected trend of increasing J as v(x) increased from approximately 2 to 30 m/day. The LE model and the NE model with an average mass transfer coefficient, k(l)=4.76 m/day, were able to describe the neat toluene pool data for v(x)<18 m/day reasonably well. However, for v(x)>18 m/day, the NE model with k(l)=4.76 m/day provides a better description of the data, suggesting that the equilibrium boundary condition may become invalid for very high velocities. The experiments with the binary toluene in dodecane pools also show the expected trend of increasing J with increasing v(x). The LE model describes the binary pool data reasonably well for the entire range of v(x) studied (approximately 0.1 to 10 m/day), and the NE model predictions with the average k(l)=4.76 m/day determined in the neat-pool studies do not deviate significantly from the LE model in this v(x) range, although small deviations occur for >10 m/day. Copyright (C) 1999 Elsevier Science B.V.

KW - Dissolution

KW - Experimental studies

KW - Flushing

KW - NAPL (nonaqueous phase liquid)

KW - Pool

KW - Toluene

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U2 - 10.1016/S0169-7722(98)00157-0

DO - 10.1016/S0169-7722(98)00157-0

M3 - Article

AN - SCOPUS:0033023715

SN - 0169-7722

VL - 37

SP - 111

EP - 137

JO - Journal of Contaminant Hydrology

JF - Journal of Contaminant Hydrology

IS - 1-2

ER -