Nonideal transport of reactive solutes in heterogeneous porous media 5. Simulating regional-scale behavior of a trichloroethene plume during pump-and-treat remediation

Zhihui Zhang, Mark L Brusseau

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

'Pump and treat' is widely used for containment and remediation of groundwater contaminant plumes. However, it is commonly observed that pump-and-treat systems begin to exhibit reduced efficiency at some point. A number of factors and processes may contribute to the reduced efficiency, among them being those associated with nonideal transport behavior, such as subsurface heterogeneity, nonlinear, rate-limited sorption/desorption, and rate-limited dissolution of immiscible liquid. We use numerical modeling to analyze the regional-scale (~49 km2) nonideal transport behavior of trichloroethene in a contaminated aquifer undergoing pump and treat remediation. The pump-and-treat system has been in operation for ~12 years, during which time the composite concentrations of trichloroethene in the treatment plant influent have decreased from >300 to ~100 μg L-1. However, as is typically observed elsewhere, the system is exhibiting extensive concentration tailing, wherein the concentrations have remained relatively constant at ~100 μg L-1 for the past 8 years. Various factors that may be contributing to this tailing phenomenon are evaluated using a three-dimensional solute transport model specifically developed for the site, which is located in Tucson, Arizona. The values for almost all of the input parameters of the model were obtained independently of the historic concentration data being simulated. The hydraulic conductivity field was generated using information obtained from borehole logs and pumping tests, the sorption and local-scale mass transfer parameters were obtained from laboratory experiments conducted with aquifer material collected from the site, and the initial immiscible-liquid saturations were based on the results of partitioning tracer tests conducted in a representative source zone at the site. On the basis of our analyses we conclude that while rate-limited desorption and large-scale spatial variability of hydraulic conductivity have significant impacts on trichloroethene transport, the dissolution of immiscible-liquid saturation associated with the source zones is most likely the primary cause of the extensive concentration tailing observed at the site. The impact of nonlinear sorption and local-scale mass transfer on trichloroethene removal appears to be insignificant.

Original languageEnglish (US)
Pages (from-to)2921-2935
Number of pages15
JournalWater Resources Research
Volume35
Issue number10
DOIs
StatePublished - 1999

Fingerprint

pump and treat
Trichloroethylene
porous media
remediation
trichloroethylene
Remediation
pumps
solutes
Porous materials
porous medium
solute
Tailings
plume
Pumps
tailings
sorption
Sorption
Hydraulic conductivity
Aquifers
mass transfer

ASJC Scopus subject areas

  • Aquatic Science
  • Environmental Science(all)
  • Environmental Chemistry
  • Water Science and Technology

Cite this

@article{160d75a708dd484dad7b385106e5163b,
title = "Nonideal transport of reactive solutes in heterogeneous porous media 5. Simulating regional-scale behavior of a trichloroethene plume during pump-and-treat remediation",
abstract = "'Pump and treat' is widely used for containment and remediation of groundwater contaminant plumes. However, it is commonly observed that pump-and-treat systems begin to exhibit reduced efficiency at some point. A number of factors and processes may contribute to the reduced efficiency, among them being those associated with nonideal transport behavior, such as subsurface heterogeneity, nonlinear, rate-limited sorption/desorption, and rate-limited dissolution of immiscible liquid. We use numerical modeling to analyze the regional-scale (~49 km2) nonideal transport behavior of trichloroethene in a contaminated aquifer undergoing pump and treat remediation. The pump-and-treat system has been in operation for ~12 years, during which time the composite concentrations of trichloroethene in the treatment plant influent have decreased from >300 to ~100 μg L-1. However, as is typically observed elsewhere, the system is exhibiting extensive concentration tailing, wherein the concentrations have remained relatively constant at ~100 μg L-1 for the past 8 years. Various factors that may be contributing to this tailing phenomenon are evaluated using a three-dimensional solute transport model specifically developed for the site, which is located in Tucson, Arizona. The values for almost all of the input parameters of the model were obtained independently of the historic concentration data being simulated. The hydraulic conductivity field was generated using information obtained from borehole logs and pumping tests, the sorption and local-scale mass transfer parameters were obtained from laboratory experiments conducted with aquifer material collected from the site, and the initial immiscible-liquid saturations were based on the results of partitioning tracer tests conducted in a representative source zone at the site. On the basis of our analyses we conclude that while rate-limited desorption and large-scale spatial variability of hydraulic conductivity have significant impacts on trichloroethene transport, the dissolution of immiscible-liquid saturation associated with the source zones is most likely the primary cause of the extensive concentration tailing observed at the site. The impact of nonlinear sorption and local-scale mass transfer on trichloroethene removal appears to be insignificant.",
author = "Zhihui Zhang and Brusseau, {Mark L}",
year = "1999",
doi = "10.1029/1999WR900162",
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N2 - 'Pump and treat' is widely used for containment and remediation of groundwater contaminant plumes. However, it is commonly observed that pump-and-treat systems begin to exhibit reduced efficiency at some point. A number of factors and processes may contribute to the reduced efficiency, among them being those associated with nonideal transport behavior, such as subsurface heterogeneity, nonlinear, rate-limited sorption/desorption, and rate-limited dissolution of immiscible liquid. We use numerical modeling to analyze the regional-scale (~49 km2) nonideal transport behavior of trichloroethene in a contaminated aquifer undergoing pump and treat remediation. The pump-and-treat system has been in operation for ~12 years, during which time the composite concentrations of trichloroethene in the treatment plant influent have decreased from >300 to ~100 μg L-1. However, as is typically observed elsewhere, the system is exhibiting extensive concentration tailing, wherein the concentrations have remained relatively constant at ~100 μg L-1 for the past 8 years. Various factors that may be contributing to this tailing phenomenon are evaluated using a three-dimensional solute transport model specifically developed for the site, which is located in Tucson, Arizona. The values for almost all of the input parameters of the model were obtained independently of the historic concentration data being simulated. The hydraulic conductivity field was generated using information obtained from borehole logs and pumping tests, the sorption and local-scale mass transfer parameters were obtained from laboratory experiments conducted with aquifer material collected from the site, and the initial immiscible-liquid saturations were based on the results of partitioning tracer tests conducted in a representative source zone at the site. On the basis of our analyses we conclude that while rate-limited desorption and large-scale spatial variability of hydraulic conductivity have significant impacts on trichloroethene transport, the dissolution of immiscible-liquid saturation associated with the source zones is most likely the primary cause of the extensive concentration tailing observed at the site. The impact of nonlinear sorption and local-scale mass transfer on trichloroethene removal appears to be insignificant.

AB - 'Pump and treat' is widely used for containment and remediation of groundwater contaminant plumes. However, it is commonly observed that pump-and-treat systems begin to exhibit reduced efficiency at some point. A number of factors and processes may contribute to the reduced efficiency, among them being those associated with nonideal transport behavior, such as subsurface heterogeneity, nonlinear, rate-limited sorption/desorption, and rate-limited dissolution of immiscible liquid. We use numerical modeling to analyze the regional-scale (~49 km2) nonideal transport behavior of trichloroethene in a contaminated aquifer undergoing pump and treat remediation. The pump-and-treat system has been in operation for ~12 years, during which time the composite concentrations of trichloroethene in the treatment plant influent have decreased from >300 to ~100 μg L-1. However, as is typically observed elsewhere, the system is exhibiting extensive concentration tailing, wherein the concentrations have remained relatively constant at ~100 μg L-1 for the past 8 years. Various factors that may be contributing to this tailing phenomenon are evaluated using a three-dimensional solute transport model specifically developed for the site, which is located in Tucson, Arizona. The values for almost all of the input parameters of the model were obtained independently of the historic concentration data being simulated. The hydraulic conductivity field was generated using information obtained from borehole logs and pumping tests, the sorption and local-scale mass transfer parameters were obtained from laboratory experiments conducted with aquifer material collected from the site, and the initial immiscible-liquid saturations were based on the results of partitioning tracer tests conducted in a representative source zone at the site. On the basis of our analyses we conclude that while rate-limited desorption and large-scale spatial variability of hydraulic conductivity have significant impacts on trichloroethene transport, the dissolution of immiscible-liquid saturation associated with the source zones is most likely the primary cause of the extensive concentration tailing observed at the site. The impact of nonlinear sorption and local-scale mass transfer on trichloroethene removal appears to be insignificant.

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