Grantee Research Project Results
1998 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 , Vestal, Eric , Donahue, Timothy J. , Riffel, Allison , Ramaswami, Anuradha , Morrison, Kendra
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, 1997 through September 30, 1998
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:
Traditional environmental strategies have been found to be technologically impracticable at times contaminated with high molecular weight, multi component dense non-aqueous phase liquids (DNAPLs) due to the problems associated with complete mobilization/dissolution of the organic-phase liquid from heterogeneous subsurface systems. This project evaluates the potential of achieving risk reduction at DNAPL-contaminated sites through biological stabilization processes that focus on containing the extent of DNAPL contamination without requiring complete destruction of all the hydrophobic organic components (HOCs) derived from the DNAPL.
The overall goal of this study is to understand key factors that control the bioavailability of high molecular-weight organic contaminants sequestered within multi component DNAPLs entrapped in heterogeneous soil systems, and to optimize these factors for design of an engineered biostabilization system that may be employed to control DNAPL contamination in field situations.
This project evaluates the potential for achieving risk reduction at DNAPL-contaminated sites through microbial stabilization processes that focus on containing the extent of DNAPL contamination without requiring complete destruction of all the DNAPL constituents. The objectives of this study are threefold: (1) develop rapid screening techniques to define the end-point of DNAPL biostabilization based upon four criteria: microbial biomass, aqueous phase contaminant concentrations, aggregate toxicity of the aqueous phase, and nature of the DNAPL residue; (2) quantitatively evaluate and optimize key physicochemical and biological phenomena pertaining to DNAPL dissolution, mass transfer, bioavailability and biodegradation rates that control DNAPL stabilization in bench-scale and pilot-scale systems; and (3) develop engineering protocols for scale-up of integrated mass transfer-bioavailability-biostabilization models from small scale to large scale systems.
Progress Summary:
In the first 6 months of this project, rapid screening biostabilization tests are under way, and multicomponent degradation kinetics are being evaluated in batch systems for two DNAPLs?coal tar and a PCB (polychlorinated biphenyl) mixture (Aroclor 1242). The coal tar was obtained from a field site in Maryland. Aroclor 1242 standard (from Accustandard) is being used in the initial PCB studies. The biokinetics and biostabilization potential are being evaluated employing four aromatic solutes in coal tar, and congener 2,3'-dichlorobiphenyl in Aroclor 1242. Alcaligenes eutrophus H850, described by researchers at General Electric, are used for PCB degradation, while a mixed consortium of microbes obtained from the Maryland site is used for coal tar biodegradation.
In the multicomponent biodegradation tests, batch mixed systems are being studied with the solutes of interest considered individually and in mixtures, to determine single component and multicomponent kinetics, respectively. Single component kinetics are being compared with multicomponent kinetics to determine possible synergistic or antagonistic effects created by having a mixture of substrates available for microbial degradation. Possible mixture interactions include toxic or inhibitory effects of a substrate and/or its degradation products, competitive substrate interactions, as well as synergistic effects due to cometabolic transformations. Biokinetic data obtained from batch tests are analyzed, enabling modeling of the biodegradation of the mixture in terms of biokinetic parameters obtained for the individual substrates.
In the biostabilization tests, the DNAPL mixtures are placed in a well in batch systems attached to a respirometer. Oxygen consumption, microbial biomass, DNAPL composition, aqueous phase substrate concentrations, as well as the aggregate toxicity (Microtox test) of the aqueous phase are measured periodically over a three month test period. These data are obtained for a well-mixed system with enhanced bioavailability of the DNAPL derived solutes in the aqueous phase, as well as in a unmixed mass transfer-limited system representative of the quiescent subsurface. Preliminary results obtained over a 90 day period indicate that the mass transfer limited system shows a greater potential for biological stabilization. Although microbial concentrations are lower in this system due to slow dissolution of the substrates to the aqueous phase, the aqueous phase contaminant is consumed relatively quickly by the microbes resulting in lowered aqueous phase contaminant concentration and reduced aggregate toxicity.
The biostabilization phenomena, in which slow dissolution is coupled with more rapid biokinetics, is incorporated into a computer model developed by modular adaptations to the MT3D subsurface contaminant transport model. Simulations are presented to test model behavior in the presence of single component and multicomponent DNAPL mixtures. In future years, independent dissolution and biostabilization tests will be conducted at small and intermediate-scale systems to evaluate the potential for scaling up of biostabilization phenomena from laboratory to field conditions.
Future Activities:
In the next year, we plan to complete Phase 1 activities (Phase 1: Biostabilization Screening Tests and Biokinetic Studies) and initiate Phase 2 (Phase 2: Mass Transfer and Bioavailability). As part of Phase 1 research, the biostabilization potential of coal tar and Aroclor 1242 will be examined, and the biodegradation kinetics of biphenyl, styrene, naphthalene, methyl-naphthalene, and phenanthrene will be studied and modeled. As part of Phase 2 work, bench-scale and tank-scale systems will be designed and tested to examine the kinetics of release of contaminants from DNAPL pools at different water flow rates. Work also will be initiated on part of Phase 4 (Phase 4: Modeling and Scale-up of Laboratory Data) to modify a finite element groundwater contamination modeling software package, SUTRA, to incorporate biostabilization phenomena.Journal Articles:
No journal articles submitted with this report: View all 36 publications for this projectSupplemental Keywords:
groundwater and soil contamination, bioavailability, risk management, DNAPL, bioremediation, modeling, treatment, restoration, innovative technology., RFA, Scientific Discipline, Toxics, Waste, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Bioavailability, Environmental Chemistry, Chemistry, State, HAPS, Fate & Transport, Environmental Microbiology, Microbiology, chemical mixtures, Bioremediation, Groundwater remediation, Engineering, Environmental Engineering, fate and transport, risk-based decisions, NAPL, DNAPL, biostabilization, contaminated sediment, biodegradation, multicomponent nonaqueous phase liquids, chemical transport, subsurface systems, HOCs, contaminants in soil, Maryland (MD), chemical releases, contaminant release, sediments, California (CA)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.