Grantee Research Project Results
1998 Progress Report: Traveling Wave Behavior During Subsurface Transport of Biologically Reactive Contaminants: Implications for In Situ Bioremediation
EPA Grant Number: R824785Title: Traveling Wave Behavior During Subsurface Transport of Biologically Reactive Contaminants: Implications for In Situ Bioremediation
Investigators: Valocchi, Albert J.
Institution: University of Illinois Urbana-Champaign
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1996 through December 1, 1998 (Extended to December 31, 1999)
Project Period Covered by this Report: January 1, 1997 through December 1, 1998
Project Amount: $200,000
RFA: Water and Watersheds (1995) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
The objectives of the research are to investigate how transport and mixing processes affect the overall performance of engineered in situ bioremediation. Although these processes play a key role in the ultimate success of actual remediation projects, their significance cannot be ascertained through typical laboratory-scale studies. Therefore, we are analyzing mathematical models for a typical bioremediation scenario in which a uniformly-distributed organic contaminant is degraded by indigenous soil microbes that are stimulated by an injected material (e.g., an electron acceptor such as oxygen). Our analysis starts with simple one-dimensional homogeneous systems and progresses to more realistic multidimensional heterogeneous aquifers.Progress Summary:
We have studied the following cases: one-dimensional uniform flow in a homogeneous aquifer; ideal radial flow from an injection well in a homogeneous aquifer; and two-dimensional flow in stratified and randomly heterogeneous aquifers. For a wide variety of cases, we find that the system evolves to form traveling waves; that is, the spatial profiles of the organic pollutant, electron acceptor, and biomass attain constant shapes that travel in unison. These traveling waves form due to a balanced interaction between solute mixing processes and localized biodegradation processes. This results in a very localized reaction zone where the pollutant and electron acceptor mix together.For conditions when traveling waves exist, we have derived simple formulas to calculate the long-term rate of pollutant removal due to biodegradation. The removal rate expressions are similar for all the different flow systems that we have examined. It is surprising and significant that complex multidimensional heterogeneous aquifers behave the same as simple one-dimensional homogeneous aquifers. The pollutant removal rate depends upon transport properties of the aquifer, but it does not depend upon the initial biomass concentration or upon the rate at which the biomass can degrade the pollutant. Results from the simple formulas were verified by comparison with numerical simulations. However, the numerical simulations show that it takes a certain initial time to establish traveling wave conditions; during the initial time phase, the biodegradation rate depends, in a complex fashion, on all the reaction and transport parameters.
Future Activities:
In the remaining portion of the project period, we will complete our analysis of more realistic cases of aquifer heterogeneity where the soil permeability changes randomly in all directions. Detailed numerical simulations of the cases studied to date indicate that the traveling wave behavior is not established until a certain time elapses. We plan to study this initial time period because the biodegradation rate then is often much larger than the long-term rate that is attained after the traveling waves form. If time permits, we also will analyze the applicability of the traveling wave approach to intrinsic bioremediation (natural attenuation). We will summarize and synthesize all project findings and submit the final report.Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 9 publications | 3 publications in selected types | All 3 journal articles |
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Oya S, Valocchi AJ. Analytical approximation of biodegradation rate for in situ bioremediation of groundwater under ideal radial flow conditions. Journal of Contaminant Hydrology 1998;31(3-4):275-293. |
R824785 (1998) R824785 (Final) |
not available |
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Oya S, Valocchi AJ. Transport and biodegradation of solutes in stratified aquifers under enhanced in situ bioremediation conditions. Water Resources Research 1998;34(12):3323-3334. |
R824785 (1998) R824785 (Final) |
not available |
Supplemental Keywords:
water, groundwater, soil, adsorption, absorption, chemical transport, chemical, remediation, bioremediation, oxidation, environmental chemistry, physics, engineering, hydrology, mathematics, modeling., RFA, Scientific Discipline, Water, Waste, Water & Watershed, Hydrology, Remediation, Environmental Chemistry, Mathematics, Physics, Chemistry, Bioremediation, Groundwater remediation, Engineering, Biology, Watersheds, fate and transport, biodegradation, aquifer sediments, kinetic studies, chemical transport, adsorption, subsurface systems, traveling wave behavior, in situ bioremediation, environmental engineering, in-situ bioremediation, subsurface transport of contaminants, aquatic ecosystems, desorption rates, mathematical models, groundwater, organic contaminantsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.