Grantee Research Project Results
Final Report: The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
EPA Grant Number: R825549C038Subproject: this is subproject number 038 , established and managed by the Center Director under grant R825549
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (1989) - Great Plains/Rocky Mountain HSRC
Center Director: Erickson, Larry E.
Title: The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
Investigators: Parkin, Gene F
Institution: University of Iowa
EPA Project Officer: Hahn, Intaek
Project Period: May 1, 1992 through May 1, 1994
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (1989) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objectives of the proposed research include the following:
1. To determine the effect of redox condition (electron acceptor) on
transformation of CT
2. To identify pathways and metabolites of CT
transformation
3. To investigate the abiotic degradation of CT under reduced
conditions
4. To determine the effect of CT concentration on transformation of CT.
Summary/Accomplishments (Outputs/Outcomes):
Soil and groundwater contamination by CT has been documented at several sites within the 1 state area served by EPA Regions 7 and 8. In order to engineer in situ or above-ground biological treatment systems to remediate these sites, research is needed to understand the transformations of CT under a variety of conditions. A research program was begun at the University of Iowa approximately six months ago to provide some of this information. This proposal represents a request for second and third year support to meet the objectives listed above.
The proposed project involves a three-year experimental plan. CT is being fed to existing glass-bead reactors. These experiments are giving a preliminary indication of the effect of electron acceptor (redox) condition on the degradability of relatively low concentrations of CT. During the second half of the first year we propose to add CT at about 2mg/L to separate methanogenic filters and increase the concentration until process performance significantly decreases. Effluent samples will be analyzed for expected CT breakdown products (i.e., CF, DCM and CM).
Seed cultures will be developed for the four redox conditions. Enrichment cultures will be fed a defined nutrient media, acetate as a carbon and energy source, and CT. These enrichment cultures will be used to seed the new reactors and for batch experiments.
Initial batch studies with the developed enrichment cultures will focus on CT degradation kinetics and the kinetics of formation and disappearance of CT-degradation products. Concentrations of CT, acetate, and initial biomass will be varied.
Several researchers have hypothesized that the reported variability in CT transformation under denitrifying conditions may be due to the competition between nitrate and CT for electrons. If nitrate is removed from the feed, CT transformation was enhanced. The purpose of these experiments was to evaluate the effect of acetate, nitrate, and CT loading conditions on CT biotransformation under denitrifying conditions. Details are contained in Appendix E.
Mixed denitrifying cultures were maintained in three biofilm reactors which were operated with a 1.5-hour hydraulic retention time. Three loading conditions were used: (1) 100 mg/L acetate and 142 mg/L NO3-; (2) 50 mg/L acetate and 71 mg/L NO3-; and (3) 25 mg/L acetate and 36 mg/L NO3-. After two months of operation with no CT addition, all three reactors utilized all acetate fed and had excess NO3- in the effluent. The original intent of these experiments was to now add CT, allow the reactors to reach a new steady state, and then to remove the NO3- from the feed and see if CT removal was indeed enhanced.
Approximately 100 mg/L of CT was fed to all three reactors while maintaining the same acetate and NO3- concentrations listed above. CT removal was observed soon after it was added to the systems. Approximately 27% of the influent CT was removed in all three reactors with no CF production observed. Although volatilization could not be eliminated as a removal mechanism, separate experiments showed that it could not entirely explain the CT removal.
After approximately 55 days of CT addition, the denitrifying activity in all three reactors unexpectedly stopped. Initially, it was felt that this change in activity was due to toxicity of CT or monitored for approximately 21 days. Results showed little or no recovery of denitrifying activity; organisms were inactivated and/or washed out.
Additional experiments were conducted to determine if the observed inhibition was due to CT. Batch denitrifying cultures were incubated with approximately 200 mg/L acetate, 285 mg/l NO3-, and either 100 or 500 mg/L CT. Results from these experiments gave little evidence of short-term inhibition due to CT. It may be that the inhibition observed during the biofilm-reactor experiments was due to the build-up of CT transformation products over time. Because of the loss of denitrifying activity, experiments to evaluate the effect of nitrate availability on CT biotransformation were not conducted.
The effect of the presence of the acetate, the primary substrate, on CT and CF transformation rates and products was determined in triplicate 38-mL batch reactors containing 25 mL cell suspension from the stack culture reactor. DI and killed (autoclaved) controls showed negligible CT or CF degradation in the absence of live cells over the course of the studies. The transformation of CT or CF was analyzed by a pseudo-first-order rate coefficient defined by assuming constant biomass concentration. Values of the parameter were calculated from linear regression. Analysis of the data shows that (1) the pseudo-first order transformation rate coefficients decreased with the increasing initial concentration of CT or CF, (2) values for active cell incubations at a given initial concentration are greater than for resting cell incubations, and (3) values at a given initial concentration are approximately one order of magnitude greater for CT than for CF.
CF was produced from CT and subsequently transformed in the batch reactors. For the incubations that had initial CT concentrations of approximately 4.0 and 5.5 mM CT, a greater fraction of CT was transformed via hydrogenolysis to CF by active cells than by resting cells. CF concentration in the active cell incubation was greater than the corresponding CF concentration in the resting cell incubation. The CF transformation data shows that CF is transformed more slowly by resting cells than by active cells. Thus, active cells appear to transform a greater fraction of CT via hydrogenolysis to CR than do resting cells. This observation is especially significant in light of the finding that the transformation of CF by this mixed culture results in inactivation of acetoclastic methanogens and in a loss of cometabolic activity. The hydogenolysis pathway of both CT and CF transformation increases in the presence of acetate.
The effect of CF and CT on acetoclastic methanogenesis was investigated. Results showed that acetoclastic methanogenesis could not be isolated from the effect of CF.
The transformation of carbon tetrachloride and chloroform were investigated in duplicate 38-mL batch reactors containing 25 mL methanogenic cell suspension and iron fillings. CT and CF transformation kinetics were fastest in iron-cell (IC) treatments compared to treatments containing either resting cell suspension only, or to cell-free reactor supernatant and iron (IS treatment). We propose that the enhanced CT and CF transformation rates in the IC treatments are due to cometabolism by hydrogenotrophic methanogens. Methane production was negligible in CT- and CF-free controls containing cell suspension but no iron filings, and the IS treatment, while methane was produced in IC treatment. Also, although hydrogen was not analyzed, bubbles were seen rising form the surface of the iron in a bottle containing iron filings in DI water. Hydrogen produced by the corrosion of iron metal could be consumed by hydrogenotrophic methanogens, who then cometabolically channel reducing equivalents to CT or CF. Hydrogen is an excellent electron donor for methanogens, but he use of hydrogen as an in situ energy source for anaerobic microorganisms has been hampered by its low solubility.
The results have been presented at several professional meetings.
Journal Articles:
No journal articles submitted with this report: View all 11 publications for this subprojectSupplemental Keywords:
carbon tetrachloride, cometabolism, bioremediation, anaerobic., RFA, Scientific Discipline, Geographic Area, Waste, Water, Contaminated Sediments, Remediation, Environmental Chemistry, Geochemistry, Chemistry, Analytical Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, EPA Region, hazardous waste disposal, hazardous waste management, hazardous waste treatment, adsorbent regeneration, fate and transport, carbon tetrachloride, advanced treatment technologies, fate and transport , adsorption, contaminated soil, Region 7, Region 8, hazardous organic compounds, abiotic degradation, hazardous waste identification, hazardous waste characterization, supercritical fluids, redox, groundwaterRelevant Websites:
http://www.engg.ksu.edu/HSRC Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R825549 HSRC (1989) - Great Plains/Rocky Mountain HSRC Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825549C006 Fate of Trichloroethylene (TCE) in Plant/Soil Systems
R825549C007 Experimental Study of Stabilization/Solidification of Hazardous Wastes
R825549C008 Modeling Dissolved Oxygen, Nitrate and Pesticide Contamination in the Subsurface Environment
R825549C009 Vadose Zone Decontamination by Air Venting
R825549C010 Thermochemical Treatment of Hazardous Wastes
R825549C011 Development, Characterization and Evaluation of Adsorbent Regeneration Processes for Treament of Hazardous Waste
R825549C012 Computer Method to Estimate Safe Level Water Quality Concentrations for Organic Chemicals
R825549C013 Removal of Nitrogenous Pesticides from Rural Well-Water Supplies by Enzymatic Ozonation Process
R825549C014 The Characterization and Treatment of Hazardous Materials from Metal/Mineral Processing Wastes
R825549C015 Adsorption of Hazardous Substances onto Soil Constituents
R825549C016 Reclamation of Metal and Mining Contaminated Superfund Sites using Sewage Sludge/Fly Ash Amendment
R825549C017 Metal Recovery and Reuse Using an Integrated Vermiculite Ion Exchange - Acid Recovery System
R825549C018 Removal of Heavy Metals from Hazardous Wastes by Protein Complexation for their Ultimate Recovery and Reuse
R825549C019 Development of In-situ Biodegradation Technology
R825549C020 Migration and Biodegradation of Pentachlorophenol in Soil Environment
R825549C021 Deep-Rooted Poplar Trees as an Innovative Treatment Technology for Pesticide and Toxic Organics Removal from Soil and Groundwater
R825549C022 In-situ Soil and Aquifer Decontaminaiton using Hydrogen Peroxide and Fenton's Reagent
R825549C023 Simulation of Three-Dimensional Transport of Hazardous Chemicals in Heterogeneous Soil Cores Using X-ray Computed Tomography
R825549C024 The Response of Natural Groundwater Bacteria to Groundwater Contamination by Gasoline in a Karst Region
R825549C025 An Electrochemical Method for Acid Mine Drainage Remediation and Metals Recovery
R825549C026 Sulfide Size and Morphology Identificaiton for Remediation of Acid Producing Mine Wastes
R825549C027 Heavy Metals Removal from Dilute Aqueous Solutions using Biopolymers
R825549C028 Neutron Activation Analysis for Heavy Metal Contaminants in the Environment
R825549C029 Reducing Heavy Metal Availability to Perennial Grasses and Row-Crops Grown on Contaminated Soils and Mine Spoils
R825549C030 Alachlor and Atrazine Losses from Runoff and Erosion in the Blue River Basin
R825549C031 Biodetoxification of Mixed Solid and Hazardous Wastes by Staged Anaerobic Fermentation Conducted at Separate Redox and pH Environments
R825549C032 Time Dependent Movement of Dioxin and Related Compounds in Soil
R825549C033 Impact of Soil Microflora on Revegetation Efforts in Southeast Kansas
R825549C034 Modeling the use of Plants in Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances
R825549C035 Development of Electrochemical Processes for Improved Treatment of Lead Wastes
R825549C036 Innovative Treatment and Bank Stabilization of Metals-Contaminated Soils and Tailings along Whitewood Creek, South Dakota
R825549C037 Formation and Transformation of Pesticide Degradation Products Under Various Electron Acceptor Conditions
R825549C038 The Effect of Redox Conditions on Transformations of Carbon Tetrachloride
R825549C039 Remediation of Soil Contaminated with an Organic Phase
R825549C040 Intelligent Process Design and Control for the Minimization of Waste Production and Treatment of Hazardous Waste
R825549C041 Heavy Metals Removal from Contaminated Water Solutions
R825549C042 Metals Soil Pollution and Vegetative Remediation
R825549C043 Fate and Transport of Munitions Residues in Contaminated Soil
R825549C044 The Role of Metallic Iron in the Biotransformation of Chlorinated Xenobiotics
R825549C045 Use of Vegetation to Enhance Bioremediation of Surface Soils Contaminated with Pesticide Wastes
R825549C046 Fate and Transport of Heavy Metals and Radionuclides in Soil: The Impacts of Vegetation
R825549C047 Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants
R825549C048 Acid-Producing Metalliferous Waste Reclamation by Material Reprocessing and Vegetative Stabilization
R825549C049 Laboratory and Field Evaluation of Upward Mobilization and Photodegradation of Polychlorinated Dibenzo-P-Dioxins and Furans in Soil
R825549C050 Evaluation of Biosparging Performance and Process Fundamentals for Site Remediation
R825549C051 Field Scale Bioremediation: Relationship of Parent Compound Disappearance to Humification, Mineralization, Leaching, Volatilization of Transformaiton Intermediates
R825549C052 Chelating Extraction of Heavy Metals from Contaminated Soils
R825549C053 Application of Anaerobic and Multiple-Electron-Acceptor Bioremediation to Chlorinated Aliphatic Subsurface Contamination
R825549C054 Application of PGNAA Remote Sensing Methods to Real-Time, Non-Intrusive Determination of Contaminant Profiles in Soils
R825549C055 Design and Development of an Innovative Industrial Scale Process to Economically Treat Waste Zinc Residues
R825549C056 Remediation of Soils Contaminated with Wood-Treatment Chemicals (PCP and Creosote)
R825549C057 Effects of Surfactants on the Bioavailability and Biodegradation of Contaminants in Soils
R825549C058 Contaminant Binding to the Humin Fraction of Soil Organic Matter
R825549C059 Identifying Ground-Water Threats from Improperly Abandoned Boreholes
R825549C060 Uptake of BTEX Compounds by Hybrid Poplar Trees in Hazardous Waste Remediation
R825549C061 Biofilm Barriers for Waste Containment
R825549C062 Plant Assisted Remediation of Soil and Groundwater Contaminated by Hazardous Organic Substances: Experimental and Modeling Studies
R825549C063 Extension of Laboratory Validated Treatment and Remediation Technologies to Field Problems in Aquifer Soil and Water Contamination by Organic Waste Chemicals
The 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.
Project Research Results
Main Center: R825549
904 publications for this center
182 journal articles for this center