2004 Progress Report: Novel Methods for Laboratory Measurement of Transverse Dispersion in Porous MediaEPA Grant Number: R828772C013
Subproject: this is subproject number 013 , established and managed by the Center Director under grant R828772
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (2001) - Western Region Hazardous Substance Research Center for Developing In-Situ Processes for VOC Remediation in Groundwater and Soils
Center Director: Semprini, Lewis
Title: Novel Methods for Laboratory Measurement of Transverse Dispersion in Porous Media
Investigators: Kitanidis, Peter K. , Criddle, Craig C.
Institution: Stanford University
EPA Project Officer: Lasat, Mitch
Project Period: September 1, 2001 through August 31, 2006
Project Period Covered by this Report: September 1, 2003 through August 31, 2004
RFA: Hazardous Substance Research Centers - HSRC (2001) RFA Text | Recipients Lists
Research Category: Land and Waste Management , Hazardous Waste/Remediation
(1) Develop, refine, and critically evaluate novel methods for the laboratory measurement of transverse dispersion in homogeneous isotropic unconsolidated porous media; (2) develop experimental protocols and methods of data analysis; (3) independently verify the accuracy of the new methods; (4) perform extensive experiments to determine relations of transverse dispersivity with conductivity, longitudinal dispersivity, mean grain size, degree of non-uniformity, etc.
Transverse dispersion in porous media measures the rate of spreading of a solute in the direction perpendicular to flow. Pore-scale transverse dispersion is widely accepted as playing a dominant role in determining the actual rate of dilution of solutes and mixing of reactants in porous media. For example, consider a long plume of contaminants emanating from a constant source. The rate of intrinsic remediation is determined by the rate of transverse mixing of contaminants in the plume with reactants from the surrounding groundwater. The rate may be primarily determined by the value of the transverse dispersion coefficient. Better understanding of transverse dispersion would ultimately improve our understanding of diffusion-limited processes, such as intrinsic remediation. Despite its importance, transverse dispersion remains insufficiently understood.
Part of the difficulty has been the lack of accurate and efficient methods for laboratory measurements. In most existing methods for the determination of transverse dispersion, the measured quantity is proportional to the dispersion coefficient, and thus is small and swamped by experimental error. However, we have developed new methods for the measurement of local transverse dispersion in isotropic porous media based on a helical and a cochlea-like device. The idea is to perform an experiment similar to the tracer test through a laboratory column packed with a porous medium and to measure the breakthrough curve; however, the objective is not to determine the column-scale longitudinal dispersion but the transverse dispersion. The principle is to induce shear flow inside the device that creates strong longitudinal dispersion in the observed breakthrough curve; transverse mixing tends to negate the effects of shear flow and thus reduce the observed column-scale longitudinal dispersion. Then, from the spreading of the observed breakthrough curve, we can estimate the unknown, the pore-scale transverse dispersion. The measured quantity varies inversely with the transverse dispersion coefficient.
We have been conducting experiments with a newly constructed cochlear device to evaluate the transverse dispersion for glass beads at the size of coarse sand. The cochlear device is easier to pack (i.e., fill the tube with the granular material) than the helical one, and the analysis of the data is easier. Nevertheless, it is always a challenge to pack a device in a uniform fashion and to prevent the entrapment of gas in the porous medium. We are comparing the results with those obtained in a helix.
Student Working on the Project
Ioannis Benekos, Ph.D. candidate, Department of Civil and Environmental Engineering, Stanford University.
Journal Articles:No journal articles submitted with this report: View all 6 publications for this subproject
Progress and Final Reports:Original Abstract
Main Center Abstract and Reports:R828772 HSRC (2001) - Western Region Hazardous Substance Research Center for Developing In-Situ Processes for VOC Remediation in Groundwater and Soils
Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828772C001 Developing and Optimizing Biotransformation Kinetics for the Bio- remediation of Trichloroethylene at NAPL Source Zone Concentrations
R828772C002 Strategies for Cost-Effective In-situ Mixing of Contaminants and Additives in Bioremediation
R828772C003 Aerobic Cometabolism of Chlorinated Aliphatic Hydrocarbon Compounds with Butane-Grown Microorganisms
R828772C004 Chemical, Physical, and Biological Processes at the Surface of Palladium Catalysts Under Groundwater Treatment Conditions
R828772C005 Effects of Sorbent Microporosity on Multicomponent Fate and Transport in Contaminated Groundwater Aquifers
R828772C006 Development of the Push-Pull Test to Monitor Bioaugmentation with Dehalogenating Cultures
R828772C007 Development and Evaluation of Field Sensors for Monitoring Bioaugmentation with Anaerobic Dehalogenating Cultures for In-Situ Treatment of TCE
R828772C008 Training and Technology Transfer
R828772C009 Technical Outreach Services for Communities (TOSC) and Technical Assistance to Brownfields Communities (TAB) Programs
R828772C010 Aerobic Cometabolism of Chlorinated Ethenes by Microorganisms that Grow on Organic Acids and Alcohols
R828772C011 Development and Evaluation of Field Sensors for Monitoring Anaerobic Dehalogenation after Bioaugmentation for In Situ Treatment of PCE and TCE
R828772C012 Continuous-Flow Column Studies of Reductive Dehalogenation with Two Different Enriched Cultures: Kinetics, Inhibition, and Monitoring of Microbial Activity
R828772C013 Novel Methods for Laboratory Measurement of Transverse Dispersion in Porous Media
R828772C014 The Role of Micropore Structure in Contaminant Sorption and Desorption