Grantee Research Project Results
1999 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, 1998 through September 30, 1999
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.
The project consists of the following four phases:
Phase 1: Biostabilization Screening Tests and Biokinetic Studies. Bench-scale biostabilization screening tests are developed to examine the potential for biostabilization of various DNAPLs. The protocols are tested with DNAPL coal tar (composed of a mix of PAHs), and an Aroclor DNAPL (composed of a mix of PCBs). Phase 1 research also examines the biodegradation kinetics of individual PAH and PCBs in the absence of mass transfer constraints.
Phase 2: Mass Transfer and Bioavailability. Tests measure the equilibrium partitioning and kinetics of release of multiple organic compounds from DNAPL in two abiotic tank systems: a small-scale, bench-top system and a larger, pilot-scale system. The goal is to determine key factors that control the availability of organic contaminants released from DNAPL pools, at two different spatial scales.
Phase 3: Biostabilization. Tests examine the combined effect of contaminant dissolution from DNAPLs and microbial degradation on stabilization and risk reduction at two spatial scales.
Phase 4: Modeling and Scale-up of Laboratory Data. The goal is to develop mathematical models and engineering protocols that would enable scale-up of biostabilization processes (mass transfer and biokinetics) from the bench-scale to the tank-scale, ultimately to the field.
Progress Summary:
The work to-date in Years 1 and 2 has resulted in completion of Phase 1 activities, and steady progress in Phase 2 and Phase 4 research. As part of Phase 1 research, the biostabilization potential of coal tar and Aroclor 1242 has been examined, and the biodegradation kinetics of biphenyl, styrene, naphthalene, methyl-naphthalene and phenanthrene have been studied and modeled. As part of Phase 2 work, bench-scale and tank-scale systems have been designed and tested to examine the kinetics of release of contaminants from DNAPL pools at different water flow rates. Diagnostic tests with octanol and coal tar revealed problems in localizing and immobilizing the DNAPL pool, due to which a smaller pilot-scale tank was designed and constructed with glass and metal walls. A bench-scale cell has also been developed and tested with solid naphthalene. Both systems are currently being operated to assess mass transfer from DNAPL pools at the small-scale and the intermediate-scale. We are evaluating current methods used to model NAPL pool dissolution as they may place limitations on modeling dissolution under biomass at the pool-water interface. A new modeling methodology that uses a local dispersivity that gets modified due to biomass growth is proposed and tested in our ongoing research. As part of Phase 4 work, a finite element groundwater contamination modeling software package, SUTRA, is under modification to incorporate biostabilization phenomena. These modifications involve the incorporation of multiple species in the transport equations, incorporating bio-kinetics and bio-growth, and modeling of oxygen supply, modification of hydraulic conductivity field due to biomass growth and biomass transport.
Research Results. Results from Phase 1 research are presented in this section. This work has resulted in successful completion of an M.S thesis and an M.S. report by two students, Ms. Allison Riffel (University of Colorado, Boulder) and Ms. Kendra Morrison (University of Colorado, Denver) who examined biodegradation of PCBs and PAHs, respectively. The Monod model was found to describe the biodegradation kinetics of biphenyl, naphthalene and methyl naphthalene, with the following average estimated parameter values: biphenyl: Ks=22 mg/L, k= 0.3 mg biphenyl/mg VSS-hr, Y=1 g VSS/g biphenyl; naphthalene: Ks=0.5 mg/L, k= 1.4 mg naph./mg VSS-hr, Y=0.83; m-naphthalene: Ks=0.006 mg/L, k=4.3 mg m-naph./mg VSS-hr, Y=0.83. Styrene exhibited toxicity to the microbes at a concentration > ~15 mg/L. Phenanthrene exhibited first order kinetics with a degradation rate constant of 1.8 L/mg VSS-hr. The biostabilization screening tests indicated potential for biostabilization of both coal tar and Aroclor. Unlike coal tar, which demonstrated stabilization of aggregate aqueous phase toxicity, DNAPL composition (depletion of more soluble PAHs), as well as microbial counts after a 100-day period, Aroclor studies revealed stabilization of two parameters: DNAPL composition (depletion of higher solubility congeners) and microbial counts. Aqueous phase PCB concentrations were not significantly different from controls and aggregate aqueous-phase toxicity is currently being re-evaluated.
Future Activities:
In the next year, we will assess degradation of multiple PAHs released from coal tar, examine the impact of biogrowth on aquifer properties, and the subsequent impact on coal tar pool dissolution and biostabilization.Journal Articles:
No journal articles submitted with this report: View all 36 publications for this projectSupplemental Keywords:
bioavailability, biostabilization, DNAPLs, PAHs, PCBs, pool dissolution., 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.