![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20081105165415im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Final Report: Searching for Optimum Composition of Phosphogypsum: Fly ash: Cement Composites for Oyster Culch Materials
EPA Grant Number: R828598C759Subproject: this is subproject number 759 , established and managed by the Center Director under grant R828598
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Gulf Coast HSRC (Lamar)
Center Director: Ho, Tho C.
Title: Searching for Optimum Composition of Phosphogypsum: Fly ash: Cement Composites for Oyster Culch Materials
Investigators: Rusch, Kelly Ann , Malone, Ronald F.
Institution: Louisiana State University
EPA Project Officer: Krishnan, Bala S.
Project Period: September 1, 2000 through August 31, 2004
RFA: Gulf Coast Hazardous Substance Research Center (Lamar University) (1996)
Research Category: Hazardous Waste/Remediation , Targeted Research
Description:
Objective:Phosphogypsum (phosphogypsumCaSO4·2H2O) is a waste by-product of a wet manufacturing process in which phosphate ore is reacted with sulfuric acid to produce phosphoric acid :
Ca10(PO4)6sF2 + 10H2SO4 + 20H2O → 10CaSO4×2H2O + 6H3PO4 + 2HF
The wet process produces large volumes of phosphogypsum containing trace metals (ppm levels of As, Ba, Cd, Cr, and Pb) and radioactive contaminants (Radium-226 [Ra226]and Uranium) that pose potential environmental problems. Ra226 is of particular importance, with approximately 80 percent of that originally existing in the ore being concentrated in the phosphogypsum by-product. Ra226 decays to radon gas (Rn222) with intense radiation capacity and a short half-life (3.8 days). Rn222 decay results in the emission of alpha rays, which can do extensive damage to internal organs if ingested. Consequently, radon is classified as a cancer causing, radioactive gas . Emission concerns led to the promulgation of disposal/usage guidelines under the National Emission Standards for Hazardous Air Pollutants and the National Emissions Standards for Radon Emission from Phosphogypsum Stacks (Federal Register, 40 CFR Part 61 Subpart 61, February 3, 1999).
For every metric ton of phosphoric acid produced, approximately 4.4 to 4.5 metric tons of phosphogypsum is generated. The annual production rate of phosphogypsum ranges from 36.3 to 42.6 million metric tons in the United States. After water recovery and evaporation, large phosphogypsum stacks covering as much as 3 km2 and up to 60 m high are formed. Two-thirds of these stacks are located in Florida, Texas, Illinois, and Louisiana. The total surface area covered by stacks is about 34 km2, with more than one-half that area located in Florida.
The accumulation of phosphogypsum stacks causes significant space and environmental problems, placing increasing pressure on the fertilizer industry to find long-term solutions. Various alternatives for using phosphogypsum beneficially are being sought to decrease risks to humans and the environment, to reduce the cost of storage, and to create an economic market for phosphogypsum products. One alternative is the use of stabilized phosphogypsum in the marine environment for aquatic resource enhancement and coastal restoration. Preliminary laboratory data indicated that Portland type I cement-stabilized phosphogypsum composites support a diverse population of surface-attached, burrowing organisms and oysters, and that bioaccumulation is not a significant pathway of radium transfer. Most other proposed economic uses aimed at reducing the phosphogypsum accumulation rate (agriculture, roadbed aggregate, building materials, etc.) have potential problems associated with this fundamental issue of vector transmission.
Currently, composites using Portland type II cement and Class C fly ash have shown the most promise to produce phosphogypsum composites that can compete economically with other materials (mostly limestone or granite based). The Portland type II cement content must be less than 5 percent on a dry weight basis. Research prior to this project showed that the 62 percent:35 percent:3 percent, phosphogypsum:Class C fly ash:Portland type II cement composite could survive in seawater for more than 2 years. Although this composition meets the less than 5 percent cement criterion, the admixture composition has not been optimized. Optimizations may lead to reduced costs.
The objective of this research project was to determine optimal ingredient combinations within the range of 20-35 percent Class C fly ash and 1-3 percent Portland type II cement for use as aquatic enhancement material and coastal protection devices. Calcium and sulfate effective diffusion coefficients are indicators of the long term stability of the stabilized phosphogypsum composites. The objective of the first phase of this research project was to determine Ca2+ and SO42- effective diffusion coefficients for a series of ingredient combinations of stabilized phosphogypsum composites and to select several economical phosphogypsum:fly ash:cement composite combinations for evaluation of physical integrity and survivability when submerged in saltwater. The specific objective of phase two of this research project was to determine the longevity of the stabilized phosphogypsum composite compositions selected from phase one research when submerged under saltwater conditions. The specific objectives of phase three of the research project were to: (1) compare the effective porosity calculated from effective diffusion coefficients with the porosities from the weight difference measurements; (2) investigate the porosity in the phosphogypsum composites after submergence test; and (3) investigate the microstructure of the selected phosphogypsum composites.
Summary/Accomplishments (Outputs/Outcomes):Phase one included the fabrication of nine composites of Phosphogypsum:Class C fly ash:Portland type II cement and subsequent dynamic leach testing in 20 parts per thousand artificial saltwater. Dried phosphogypsum was crushed and passed through a 1.46 mm sieve and the phosphogypsum powder was combined with dry, fresh Portland type II cement and Class C fly ash at specified ingredient percentages based on dry solids mass. The dry ingredients were combined and homogenized with 8 percent water (dry mass basis), and 89 grams of the resulting mixture was poured into a 3.9 cm diameter steel mold and compacted to a 3.6 cm long cylinder under a pressure of 9.8´107 N/m2 using a static press. The composites were cured at room temperature and 100 percent humidity for more than 2 weeks. The mean mass of all composites was 87.1 grams, resulting in a solid density of 2.05 g/cm3.
A variation of the dynamic leach test was performed to determine calcium and sulfate release rates from the phosphogypsum composites. The leachant was exchanged completely at intervals of 0.08, 0.29, 1, 2, 3, 4, 5, 8, 11, 14, 21, and 28 days. The leachate was analyzed for calcium, sulfate, and alkalinity in accordance to standard methods. Calcium and sulfate ion release from the phosphogypsum composite can be considered nonreactive. Thus, the diffusive flux of calcium and sulfate ions can then be estimated by Fick’s second law. Calcium effective diffusion coefficient (De) ranged from 1.13 to 2.71 X 10-13 m2·s-1, whereas effective diffusion depth ranged from 14.8 to 22.7 mm for 30 years submergence. These values are comparable to the values from previous research (10-13 – 10-14 m2·s-1) for Phosphogypsum:Class C fly ash:Portland type II cement composites. Sulfate effective diffusion coefficient (De) ranged from 1.41 to 3.85 X 10-13 m2·s-1, whereas effective diffusion depth ranged from 16.4 to 27.0 mm for 30 years.
The research showed that the combinations of 77 percent:20 percent:3 percent; 72 percent:25 percent:3 percent; 67 percent:30 percent:3 percent; and 63 percent:35 %:2 % Phosphogypsum:Class C fly ash:Portland type II cement composites met the 2.0 X 10-13 m2·s-1 criteria for effective calcium and sulfate diffusion coefficients and were selected for phase two studies. The estimated commercial production costs ranged from $9.34-$11.00/ton. The cost of previous optimum ingredient (62%:35%:3% Phosphogypsum:Class C fly ash:Portland type II cement) is $11.84/ton.
Phase two included field submergence of the selected phosphogypsum composites, physical observations and measurements over 9 months, and statistical quality control analysis. The field observations showed that three out of nine 72 %:25 %:3 %t and 77 %:20 %:3 % Phosphogypsum:Class C fly ash:Portland type II cement composites came out of the color tags, and two out of nine phosphogypsum composites came out of the color tags for the ingredient combinations of 67 %:30 %:3 % Phosphogypsum:Class C fly ash:Portland type II cement composite. All nine 63 %:35 %:2 % Phosphogypsum:Class C fly ash:Portland type II cement composites maintained their physical integrity. Degradation and survival cases of each ingredient combination were used to run SAS quality control analysis to determine the best-fit probability distribution of degradation cases. The Weibull probability distribution was found to represent the survivability of the composites. For the 72% :25 %:3 % Phosphogypsum:Class C fly ash:Portland type II cement composite, 50 % degradation cases are expected to happen after 10 months of submergence. For 77 %:20 %:3 % and 67 %:30 %:3 % Phosphogypsum:Class C fly ash:Portland type II cement composite, 50 % degradation cases are expected to happen after 9.8 months of submergence. No degradation case was found for the 63 %:35 %:2 % Phosphogypsum:Class C fly ash:Portland type II cement composites after 9 months of submergence, thus this combination can survive on a long-term basis.
Phase three tasks included determining apparent porosity by measuring weight loss under submerged conditions and conducting microstructure analysis. The scanning electron microscopy, microprobe, and Fourier transform infrared spectroscopy analyses of selected phosphogypsum composites indicated that a calcium carbonate coating was formed on the phosphogypsum composites (63%:35%:3% and 63%:35%:2% Phosphogypsum:Class C fly ash:Portland type II cement)/saltwater interface. This coating serves as a barrier to prevent the saltwater from intrusion. No evidence of significant saltwater intrusion was found on the phosphogypsum composites. Most of the pore sizes for leached 63 %:35 %:3 % and 63 %:35 %:2 % Phosphogypsum:Class C fly ash:Portland type II cement composites were less than 2 mm. The comparison of the apparent porosities from weight loss and effective porosities from effective diffusion coefficient measurement showed that the effective porosities from effective diffusion coefficients were only about 20 % of apparent porosities obtained from weight loss measurements. This means that only 20 %of saturated pore spaces allows saltwater to circulate and about 80 % of pore spaces are isolated pores, implying that 80 %of pore spaces are isolated.
Supplemental Keywords:phosphogypsum, diffusion coefficient, calcium ions, sulfate ions, survivability, microstructures, SEM, pollution prevention, waste treatment, site remediation, advanced treatment technologies, bioremediation, hazardous waste treatment, HSRC,
,
INDUSTRY, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, Scientific Discipline, Waste, RFA, POLLUTION PREVENTION, waste reduction, Waste Treatment, Hazardous Waste, Environmental Engineering, cleaner production/pollution prevention, Environmental Chemistry, Hazardous, Economics and Business, Industries, risk assessment, fly ash, bioaccumulation, waste recovery, economic analysis, phosphogypsum, engineering, product design, waste minimization, environmentally conscious manufacturing, radium, alternative materials, hazardous substance disposal, hazardous waste disposal, Production/Pollution Prevention, construction industry, production processes, chemically activated fly ash, construction material
Relevant Websites:
Progress and Final Reports:
2001 Progress Report
Original Abstract
Main Center Abstract and Reports:
R828598 Gulf Coast HSRC (Lamar)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R822721C529 Environmentally Acceptable Endpoints: Risk Based Remediation Using Bioremediation
R822721C552 Degradative Solidification/Stabilization Technology for Chlorinated Hydrocarbons
R822721C569 Treatment and Product Recovery: Supercritical Water Oxidation of Nylon Monomer Manufacturing Waste
R822721C620 Colloidal Fouling of Membranes: Implications in the Treatment of Textile Dye Wastes and Water Reuse
R822721C626 Catalytic Hydroprocessing of Chlorinated Organics
R822721C627 The Interaction of Microbial Activity and Zero Valent Iron Permeable Barrier Technology
R822721C630 Microbial Cometabolism of Recalcitrant Chemicals in Contaminated Air Streams
R822721C633 Catalyst Lifetime Studies for Chlorocarbon Steam Reforming
R822721C635 Electrokinetic/Surfactant-Enhanced Remediation of Hydrophobic Pollutants in Low Permeability Subsurface Environments
R822721C636 Transformation Reactions of Nitroaromatic and Nitrogen Heterocyclic Compounds on Granular Activated Carbon (GAC) Surfaces: Enhancement of GAC Adsorption in Natural and Engineered Environmental Systems
R822721C640 Environmentally Friendly Organic Synthesis in Supercritical Fluids
R822721C645 Development and Evaluation of an Integrated Model to Facilitate Risk-Based Corrective Action at Superfund Sites
R822721C651 Adjustable Biopolymer Chelators for Cadmium, Lead and Mercury
R822721C653 New Electrochemically Smart Catalysts for Hazardous Waste Management and Development of Capillary Electrophoresis for Analysis of their Products
R822721C655 Soil Sampling in South Alabama Oil Fields
R822721C659 Subsurface Contamination Site Characterization via a Computer-Aided Visual Tool
R822721C661 New Insoluble supports for Protein Immobilization for Use in Metalloprotein Affinity Metal Chromatography
R822721C663 Soil Remediation with Ultra-High-Efficiency Hydrocyclones
R822721C669 Solid Acid Catalyzed Alkylation in Supercritical Fluids
R822721C679 Regeneration/Reactivation of Carbon Adsorbents by Radio Frequency (RF) Induction Heating
R822721C687 Improved Halogen Resistance of Catalytic Oxidation
R822721C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R822721C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
R822721C700 Effects of Natural and Cyclic Variations on Contaminant Fate and Transport
R822721C703 Enhancement of DNAPL Dissolution Rates by Dechlorinating Anaerobes
R826694C620 Colloidal Fouling of Membranes: Implications in the Treatment of Textile Dye Wastes and Water Reuse
R826694C625 Enhanced Treatment of DNAPLs Contaminated Soils and Groundwater Using Biosurfactants: In-Situ Bioremediation
R826694C626 Catalytic Hydroprocessing of Chlorinated Wastes
R826694C627 The Interaction of Microbial Activity and Zero Valent Iron Permeable Barrier Technology
R826694C629 Biofiltration of BTEX in Petroleum-Contaminated Soil Remediation Off-Gas
R826694C630 Microbial Cometabolism of Recalcitrant Chemicals in Contaminated Air Streams
R826694C633 Catalyst Lifetime Studies for Chlorocarbon Steam Reforming
R826694C635 Electrokinetic/Surfactant-Enhanced Remediation of Hydrophobic Pollutants in Low Permeability Subsurface Environments
R826694C636 Transformation Reactions of Nitroaromatic and Nitrogen Heterocyclic Compounds on Granular Activated Carbon (GAC) Surfaces: Enhancement of GAC Adsorption in Natural and Engineered Environmental Systems
R826694C640 Environmentally Friendly Organic Synthesis in Supercritical Fluids
R826694C645 Development and Evaluation of an Integrated Model to Facilitate Risk-Based Corrective Action at Superfund Sites
R826694C651 Adjustable Biopolymer Chelators for Cadmium, Lead, and Mercury Remeidation
R826694C659 Subsurface Contamination Site characterization Via a Computer-Aided Visual Tool
R826694C661 New Insoluble supports for Protein Immobilization for Use in Metalloprotein Affinity Metal Chromatography
R826694C669 Solid Acid Catalyzed Alkylation in Supercritical Reaction Media
R826694C679 Regeneration and Reactivation of Carbon Adsorbents by Radio Frequency Induction Heating
R826694C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R826694C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
R826694C700 Effects of Natural Cyclic Variations on Contaminated Fate and Transport
R826694C703 Enhancement of DNAPL Dissolution Rates by Dechlorinating Anaerobes
R826694C705 A Pilot Plant for Producing Mixed Ketones from Waste Biomass
R826694C722 The Effects of an Oily-Phase on VOC Emissions from Industrial Wastewater
R826694C724 Mercury Removal from Stack Gas by Aqueous Scrubbing
R826694C725 Transport, Fate and Risk Implications of Environmentally Acceptable Endpoint Decisions
R826694C731 Development and Application of a Real-Time Optical Sensor for Atmospheric Formaldehyde
R826694C734 An Advanced System for Pollution Prevention in Chemical Complexes
R828598C001 Field Study Abstract: A Model of Ambient Air Pollution in Southeast Texas Using Artificial Neural Network Technology
R828598C002 Hollow Fiber Membrane Bioreactors for Treating Water and Air Streams Contaminated with Chlorinated Solvents
R828598C003 Fugitive Emissions of Hazardous Air Pollutants from On-Site Industrial Sewers
R828598C004 Biofiltration Technology Development
R828598C005 A Risk-Based Decision Analysis Approach for Aquifers Contaminated with DNAPLs
R828598C006 In-Situ Remediation for Contaminated Soils Using Prefabricated Vertical Drains
R828598C007 Membrane Technology Selection System for the Metal Finishing Industry
R828598C008 Sequential Environments for Enhanced Bioremediation of Chlorinated Aliphatic Hydrocarbons
R828598C009 Waste Minimization in the Magnetic Tape Industry: Waterborne Coating Formulations for Magnetic Tape Manufacture
R828598C010 Soil Remediation by Agglomeration with Petroleum Coke
R828598C011 Recovery of Dilute Phosphoric Acid in Waste Streams Using Waste Gas Ammonia: The Regenerative MAP/DAP Process
R828598C012 Stochastic Risk Assessment for Bioremediation
R828598C013 Selective Removal of Heavy Metals from Wastewater by Chelation in Supercritical Fluids
R828598C014 Optimization of Treatment Technologies for Detoxification of PCB Contaminated Soils
R828598C015 Wastewater Remediation by Catalytic Wet Oxidation
R828598C016 Permanence of Metals Containment in Solidified and Stabilized Wastes
R828598C017 Combustion Enhancement by Radial Jet Reattachment - Low Generation of Hazardous Gases and High Thermal Efficiency
R828598C018 A Process To Convert Industrial Biosludge and Paper Fines to Mixed Alcohol Fuels
R828598C019 Homogeneous Catalysis in Supercritical Carbon Dioxide
R828598C020 Ultrasonic Enhancement of the Removal of Heavy Metals
R828598C021 The Binding Chemistry and Leaching Mechanisms of Advanced Solidification/Stabilization Systems for Hazardous Waste Management
R828598C022 Development of an Air-Stripping and UV/H2O2 Oxidation Integrated Process To Treat a Chloro-Hydrocarbon-Contaminated Ground Water
R828598C023 A Comparative Study of Siting Opposition in Two Counties
R828598C024 Sonochemical Treatment of Hazardous Organic Compounds II: Process Optimization and Pathway Studies
R828598C025 Laser Diagnostics of the Combustion Process within a Rotary Kiln Incinerator
R828598C026 Use of Inorganic Ion Exchangers for Hazardous Waste Remediation
R828598C027 Kaolinite Sorbent for the Removal of Heavy Metals from Incinerated Lubricating Oils
R828598C028 Destruction of Chlorinated Hydrocarbons in Process Streams Using Catalytic Steam Reforming
R828598C029 Integrated Process Treatment Train (Bioremediation {Aerobic/Anaerobic} and Immobilization) for Texas Soils Contaminated with Combined Hazardous Wastes
R828598C030 Photo-Oxidation by H2O2/VisUV of Off-Gas Atmospheric Emissions from Industrial and Environmental Remediation Sources
R828598C031 Concentrated Halide Extraction and Recovery of Lead from Soil
R828598C032 Biodegradable Surfactant for Underground Chlorinated Solvent Remediation
R828598C033 A Software Guidance System for Choosing Analytical Subsurface Fate and Transport Models Including a Library of Computer Solutions for the Analytical Models
R828598C034 Hydrodynamic Modeling of Leachate Recirculating Landfill
R828598C035 Measurement of Oxygen Transfer Rate in Soil Matrices
R828598C036 Sorbent Technology for Multipollutant Control During Fluidized Bed Incineration
R828598C037 Pollution Prevention by Process Modification Using On-Line Optimization
R828598C038 Pollution Prevention by Process Modification
R828598C039 Water Solubility and Henry's Law Constant
R828598C040 Transferring Technical Information on Hazardous Substance Research by Publishing on the World Wide Web
R828598C041 Stress Protein Responses to Multiple Metal Exposure in Grass Shrimp
R828598C042 Life-Cycle Environmental Costing for Managing Pollution Prevention in the Chemical and Petroleum Refining Industries: A Cross-Border Approach
R828598C687 Improved Halogen Resistance of Catalytic Oxidation Through Efficient Catalyst Testing
R828598C696 Phytoremediation and Bioremediation of Land Contaminated By PAHs, PCBs, and TNT
R828598C697 Fundamental and Kinetic Investigation of Sorbent Technology for Optimum Mercury Emission Control
R828598C700 Effects of Natural Cyclic Variations on Contaminated Fate and Transport
R828598C703 Enhancement of DNAPL Dissolution Rates by Dechlorinating Anaerobes
R828598C705 A Pilot Plant for Producing Mixed Ketones from Waste Biomass
R828598C722 The Effects of an Oily-Phase on VOC Emissions from Industrial Wastewater
R828598C724 Mercury Removal from Stack Gas by Aqueous Scrubbing
R828598C725 Transport, Fate and Risk Implications of Environmentally Acceptable Endpoint Decisions
R828598C731 Development and Application of a Real Time Optical Sensor for Atmospheric Formaldehyde
R828598C734 An Advanced System for Pollution Prevention in Chemical Complexes
R828598C743 Field Demonstration of Ultrasound Enhancement of Permeable Treatment Walls
R828598C744 Optical Fibers Coated With Titania Membrane/UV-Generating Crystal in a Distributed-Light Photoreactor for VOC Oxidation
R828598C749 Characterization and Modeling of Indoor Particulate Contaminants In a Heavily Industrialized Community
R828598C753 Adsolubilization and Photocatalysis in a Semiconducting Monolithic Reactor for Wastewater Treatment
R828598C754 Remote Detection of Gas Emissions in Industrial Processes
R828598C759 Searching for Optimum Composition of Phosphogypsum: Fly ash: Cement Composites for Oyster Culch Materials
R828598C761 Development of a Phytologically-Based Biosorptive Water Treatment Process
R828598C766 Chlorinated Solvent Impact and Remediation Strategies for the Dry Cleaning Industry
R828598C769 Soil/Sediment Remediation by Hot Water Extraction Combined with In-Situ Wet Oxidation
R828598C771 Fluoracrylate Polymer Supported Ligands as Catalysts for Environmentally Benign Synthesis in Supercritical Fluids
R828598C774 The Feasibility of Electrophoretic Repair of Impoundment Leaks
R828598C777 Surfactant Enhanced Photo-oxidation of Wastewaters
R828598C778 Stationary Power Generation Via Solid Oxide Fuel Cells: A Response to Pollution and Global Warming
R828598C786 Photocatalytic Recovery of Sulfur and Hydrogen From Hydrogen Sulfide
R828598C787 Biosurfactant Produced from Used Vegetable Oil for removal of Metals From Wastewaters and Soils
R828598C789 Genetic Engineering of Enzymatic Cyanide Clearance
R828598C791 Characterizing the Intrinsic Remediation of MTBE at Field Sites
R828598C799 Simultaneous Water Conservation/Recycling/Reuse and Waste Reduction in Semiconductor Manufacturing
R828598C801 Building Defined Mixed Cultures To Biodegrade Diverse Mixtures Of Chlorinated Solvents
R828598C802 Engineering of Nanocrystal Based Catalytic Materials for Hydroprocessing of Halogenated Organics
R828598C807 Commercial Demonstration of Hydrogen Peroxide Injection to Control NOx Emissions from Combustion Sources
R828598C809 Evaluating Source Grouting and ORC for Remediating MTBE Sites
R828598C810 Application of Total Cost Assessment To Process Design In the Chemical Industry
R828598C846 Quantitative Demonstration of Source-Zone Bioremediation in A Field-Scale Experimental Controlled Release System
R831276C001 DNAPL Source Control by Reductive Dechlorination with Fe(II)
R831276C002 Arsenic Removal and Stabilization with Synthesized Pyrite
R831276C003 A Large-Scale Experimental Investigation of the Impact of Ethanol on Groundwater Contamination
R831276C004 Visible-Light-Responsive Titania Modified with Aerogel/Ferroelectric Optical Materials for VOC Oxidation
R831276C005 Development of a Microwave-Induced On-Site Regeneration Technology for Advancing the Control of Mercury and VOC Emissions Employing Activated Carbon
R831276C006 Pollution Prevention through Functionality Tracking and Property Integration
R831276C007 Compact Nephelometer System for On-Line Monitoring of Particulate Matter Emissions
R831276C008 Effect of Pitting Corrosion Promoters on the Treatment of Waters Contaminated with a Nitroaromatic Compounds Using Integrated Reductive/Oxidative Processes
R831276C009 Linear Polymer Chain and Bioengineered Chelators for Metals Remediation
R831276C010 Treatment of Perchlorate Contaminated Water Using a Combined Biotic/Abiotic Process
R831276C011 Rapid Determination of Microbial Pathways for Pollutant Degradation
R831276C012 Simulations of the Emission, Transport, Chemistry and Deposition of Atmospheric Mercury in the Upper Gulf Coast Region
R831276C013 Reduction of Environmental Impact and Improvement of Intrinsic Security in Unsteady-state
R831276C014 Integrated Chemical Complex and Cogeneration Analysis System: Greenhouse Gas Management and Pollution Prevention Solutions
R831276C015 Improved Combustion Catalysts for NOx Emission Reduction
R831276C016 A Large-Scale Experimental Investigation of the Impact of Ethanol on Groundwater Contamination
R831276C017 Minimization of Hazardous Ion-Exchange Brine Waste by Biological Treatment of Perchlorate and Nitrate to Allow Brine Recycle
R831276C018 Integrated Chemical Complex and Cogeneration Analysis System: Greenhouse Gas Management and Pollution Prevention Solutions