Grantee Research Project Results
2005 Progress Report: Reactive Transport Modeling of Metal Removal From Anaerobic Biozones
EPA Grant Number: R829515C010Subproject: this is subproject number 010 , established and managed by the Center Director under grant R829515
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for Comprehensive, optimaL, and Effective Abatement of Nutrients
Center Director: Arabi, Mazdak
Title: Reactive Transport Modeling of Metal Removal From Anaerobic Biozones
Investigators: Figueroa, Linda , Shackelford, Charles D. , Wildeman, Thomas
Institution: Colorado School of Mines , Colorado State University
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2003 through September 30, 2006
Project Period Covered by this Report: October 1, 2004 through September 30, 2005
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this research project is to develop and calibrate a model to describe the long-term microbial activity in anaerobic biozones. The investigators postulate that the proper design point for anaerobic biozones is characterized by the quasi-steady state that develops after 6 to 9 months of operation. Thus, calibration of the model based on the expected post start-up conditions is important. Post start-up conditions are characterized microbially by a balanced consortium of cellulolytic fermenters, sulfate reducers and methanogens, and substrate availability via the hydrolysis of complex organic polymers (e.g., cellulose).
Progress Summary:
A new mathematical model for the biochemical reactivity (“biomodule”) of the sulfate-reducing system has been developed, and coupled to the flow and transport models MODFLOW-2000 and RT3D v. 2.5. The primary biochemical processes encoded in this model include: (1) anaerobic bacterial decomposition of polysaccharides (cellulose-hemicellulose) releasing lactate; (2) sulfate reduction based on lactate; (3) precipitation of metal sulfides; (4) partial volatilization of hydrogen sulfide to the gas phase; and (5) reversible dissolution-precipitation of calcite (CaCO3(s)) and metal carbonates (e.g., siderite, FeCO3(s)). Additional model processes include sulfate reduction based on acetate, and competing lactate oxidation and methanogenesis. The mathematical model of biochemical reactivity has been calibrated and validated using quality experimental results from batch and column experiments obtained from the literature. Model parameter values were taken from the literature, and subsequently adjusted until model results provided good approximations of experimental results. Several sets of experimental results were employed, including four sets of batch experiments, two sets of column experiments, and three sets of bioreactor experiments. Batch and column experiments at the Colorado School of Mines (CSM) are generating data that will be used to modify a number of key kinetic parameters used in the above simulations. The inhibitory effect of mine water constituents on the rate-limiting step of cellulolytic fermenters (Cellulomonas flavigena) has been examined for zinc and copper in batch experiments. The rate and extent of cellulose degradation is a key parameter in predicting anaerobic longevity. Data from column experiments show that cellulose is not equally bioavailable in typical substrates used for anaerobic biozone construction. The cellulose-to-lignin ratio is one factor that is being examined to account for differential availability. Finally, the effect of the heterogeneous flow and transport domain on the performance of permeable reactive barriers (PRB) has been quantified using flow and particle tracking (MODFLOW-2000 and MODPATH 4.2). Probabilistic factors of safety for scaling the required extensions in PRB thickness and length as a result of aquifer heterogeneity were quantified in this component of the research. Also, values for the probabilistic factor of safety for scaling the PRB length (i.e., capture length ratio, or CLR) have been determined as a function of level of aquifer heterogeneity, aquifer correlation structure anisotropy, and distance from source zone to PRB.
Future Activities:
Future activities include calibrating the model against new batch and column testing data currently being collected at the CSM. Also, the Mine Waste Technology Program (MWTP) has approved funding for a field demonstration of sulfate reducing bioreactors using elements developed as part of two other Center projects and from previous MWTP research by MSE Technology Applications, Inc., in Butte, Montana. The drainage targeted is a neutral drainage without iron and thus previously encountered operational problems with iron precipitation using the Argo Tunnel mine water are avoided. The work plan includes collection of data sets that can be used for model validation. The field data collection will reflect temperature and metal variations over a 1.5-year period. The demonstration was scheduled to begin on March 1, 2005. Finally, samples of existing sulfate reducing bioreactor systems were provided by Golder Associates. The samples came from sites in diverse climates and at different system operational time periods. This year Amy Pruden and Linda Figueroa received supplemental funds from the U.S. Environmental Protection Agency (EPA) via David Reisman (EPA/ORD, Cincinnati) to collect samples from the same treatment systems. These samples are being analyzed for soluble carbohydrate, cellulose, and lignin composition. In addition, a fraction of these samples is being analyzed by Amy Pruden at Colorado State University for her continued evaluation of the critical microbial community structure in anaerobic biozones. This effort will generate additional field data that will be available for model calibration.
Supplemental Keywords:
bioremediation, contaminated sediments, acid mine drainage, acid mine runoff, anaerobic degradation, anaerobic microbial processes, biodegradation, contaminant transport, transport modeling, mining impacted watershed, permeable reactive barrier, sediment transport, sulfate reducing bacterium,, RFA, Scientific Discipline, Industry Sectors, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Waste, Hazardous, Remediation, Ecological Risk Assessment, Waste Treatment, Contaminated Sediments, Hazardous Waste, Geology, Mining - NAIC 21, Bioremediation, Environmental Engineering, contaminant transport, heavy metals, stream ecosystems, metal removal, anaerobic treatment, microbial degradation, mining impacted watershed, mining, acid mine drainage, treatment, suspended sediment, permeable reactive barrier, sulfate reducing bacterium, natural organic matter, mining wastes, risk assessment, redox, fate and transport modeling, transport models, remediation technologies, acid mine runoff, biodegradation, groundwater, sediment transport, field monitoring, anaerobic degradation, aquatic ecosystems, contaminated waste sites, anaerobic microbial processes, runoffRelevant Websites:
http://www.engr.colostate.edu/hsrc/ Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R829515 Center for Comprehensive, optimaL, and Effective Abatement of Nutrients Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R829515C001 Redox Transformations, Complexation and Soil/Sediment
Interactions of Inorganic Forms of As and Se in Aquatic Environments: Effects
of Natural Organic Matter
R829515C002 Fate and Transport of Metals and Sediment in Surface Water
R829515C003 Metal Removal Capabilities of Passive Bioreactor Systems: Effects of Organic Matter and Microbial Population Dynamics
R829515C004 Evaluating Recovery of Stream Ecosystems from Mining Pollution:
Integrating Biochemical, Population, Community and Ecosystem Indicators
R829515C005 Rocky Mountain Regional Hazardous Substance Research Center
Training and Technology Transfer Program
R829515C006 Technical Outreach Services for Communities and Technical Assistance to Brownfields
R829515C007 Evaluation of Hydrologic Models for Alternative Covers at Mine Waste Sites
R829515C008 Microbial Reduction of Uranium in Mine Leachate by Fermentative and Iron-Reducing Bacteria
R829515C009 Development and Characterization of Microbial Inocula for High-Performance Passive Treatment of Acid Mine Drainage
R829515C010 Reactive Transport Modeling of Metal Removal From Anaerobic Biozones
R829515C011 Assessment of Electrokinetic Injection of Amendments for Remediation of Acid Mine Drainage
R829515C012 Metal Toxicity Thresholds for Important Reclamation Plant Species of the Rocky Mountains
R829515C013 An Improved Method for Establishing Water Quality Criteria for Mining Impacted Streams
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.