Grantee Research Project Results
2000 Progress Report: Bioavailability and Biostabilization of Multicomponent Nonaqueous Phase Liquids in the Subsurface
EPA Grant Number: R825961Title: Bioavailability and Biostabilization of Multicomponent Nonaqueous Phase Liquids in the Subsurface
Investigators: Illangasekare, Tissa , Bielefeldt, Angela , Richard, Derek , Vestal, Eric , Ramaswami, Anuradha , Isleyen, Mehmet
Current Investigators: Illangasekare, Tissa , Bielefeldt, Angela , Ramaswami, Anuradha
Institution: University of Colorado at Boulder , University of Colorado at Denver , Colorado School of Mines
Current Institution: University of Colorado at Boulder , Colorado School of Mines , University of Colorado at Denver
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1997 through September 30, 2000
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $433,441
RFA: EPA/DOE/NSF/ONR - Joint Program On Bioremediation (1997) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this project is to understand key factors that control the bioavailability and biostabilization of high molecular weight organic contaminants (PAHs and PCBs) sequestered within multi-component dense non-aqueous phase liquids (DNAPLs) entrapped in heterogeneous soil systems. The main hypothesis of this project is that slow dissolution of contaminants released from DNAPL pools entrapped in the subsurface, when combined with low-level microbial activity in the vicinity of the DNAPL source region, can result in stabilization of contamination with diminished plume formation and associated risk reduction.
Progress Summary:
The work in previous years had examined the biostabilization potential of coal tar and Aroclor 1242 in small-scale batch reactors, and had measured the individual biokinetic parameters of biphenyl, styrene, naphthalene, methyl-naphthalene and phenanthrene (see 1999 progress report). Research during the October 1, 1999 to September 30, 2000, period focused on three areas: (1) measuring and modeling biodegradation of multiple PAHs released from coal tar, using single compound biokinetic data for naphthalene, phenanthrene and styrene; 2) measuring and modeling impact of microbial growth on transport properties (advection and dispersion) in an aquifer, using flow-through column studies; and (3) measuring DNAPL pool dissolution as a function of vertical dispersivity in a sand-packed tank.
Results from each of the above three focus areas are described below:
1. PAH mixture biokinetics were found to be fairly well represented by the biokinetic parameters obtained for individual PAH compounds, as shown in Figure 1. Thus, in Figure 1, the microbial degradation parameters determined for pure naphthalene in water were found to represent the degradation of aqueous-phase naphthalene released from coal tar, wherein the aqueous phase contained several other PAHs released from DNAPL coal tar. Preliminary results such as these suggest no significant effects created by the mixture, i.e., the biokinetic parameters determined for individual representative PAH compounds describe the degradation kinetics of the mixture quite adequately, although some evidence for competitive substrate inhibition was observed for methyl-naphthalene. This work was conducted by Mehmet Isleyen, Ph.D. candidate, University of Colorado, Denver, Colorado. Ongoing work will model microbial growth arising from degradation of a mixture of PAHs released from coal tar.
Figure 1. Monod model parameters determined from single substrate experiments conducted with naphthalene were found to represent the degradation of aqueous-phase naphthalene present within a mixture of PAHs released from DNAPL coal tar.
2. Impact of biogrowth on transport parameters was assessed in column systems. Protocols were developed for the design of the column systems, and the system has been successfully tested at a simulated groundwater velocity of 100 m/yr. Microbes at a concentration of 3x106 per mL are introduced into the column and the effluent was monitored to determine the attachment and transport of microbes in porous media. Bacterial attachment and transport causes an increase in longitudinal dispersivity and a decrease in the porosity of the saturated porous media, as shown in Figures 2 and 3. Ongoing work in this area, conducted by Derek Richard, M.S. student, Colorado School of Mines, is examining the effect of grain size and varying groundwater flow rates on microbial attachment, and the resulting changes in porous media properties.
3. Multicomponent DNAPL dissolution modeling has been undertaken by Eric
Vestal, Ph.D. candidate, Colorado School of Mines. A numerical finite element
code (NPDTBio: NAPL Pool Dissolution and Transport with Biodegradation) has been
developed to model 2-dimensional multicomponent DNAPL pool dissolution and
biodegradation, incorporating changes in dispersivity due to processes such as
microbial growth. The model is currently being tested with a two-component DNAPL
composed of naphthalene and hexachlorobutadiene.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 36 publications | 6 publications in selected types | All 4 journal articles |
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Bielefeldt AR, Riffel AM, Ramaswami A, Illangasekare T. Assessing multicomponent DNAPL biostabilization potential. II: Aroclor 1242. Journal of Environmental Engineering 2001;127(12):1073-1079. |
R825961 (2000) R825961 (Final) |
not available |
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Ramaswami A, Johansen PK, Isleyen M, Bielefeldt AR, Illangasekare T. Assessing multicomponent DNAPL biostabilization I: Coal tar. American Society of Civil Engineers Journal of Environmental Engineering 2001;127(12):1065-1072. |
R825961 (2000) R825961 (Final) |
not available |
Supplemental Keywords:
bioavailability, biostabilization, DNAPLs, PAHs, pool dissolution., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Geographic Area, Waste, Toxics, Engineering, Fate & Transport, State, chemical mixtures, Chemistry, HAPS, Environmental Chemistry, Groundwater remediation, Microbiology, Environmental Microbiology, Bioavailability, Bioremediation, Environmental Engineering, California (CA), sediments, contaminated sediment, HOCs, multicomponent nonaqueous phase liquids, NAPL, risk-based decisions, biodegradation, subsurface systems, fate and transport, chemical transport, DNAPL, McClellan Air Force Base, chemical releases, contaminant release, contaminants in soil, Maryland (MD)Progress 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.