Most practical combustion processes involve non-premixed combustion of hydrocarbons. To ensure that these processes are efficient and to minimize undesirable emissions, combustion should be complete and the flame temperature should be low so that NO_x emissions are low. Soot production, which can adversely affect efficiency, emissions, and equipment lifetime, must be controlled, and flame extinction must be avoided. Many methods have been considered to reduce soot, but these tend to weaken the flame, leading to extinction and reducing combustion efficiency. In this research a novel approach, called flame design, is used to design flames that best optimize efficiency and minimize pollutants, specifically soot and NO_x. Flame design attempts to affect the basic structure of the flame by varying the temperature-concentration relationship such that the peak temperature of the flame is coincident with the location of peak radical production and the oxidizing species extend deep into the fuel side of the flame to minimize the potential for formation of soot particles. Recent studies have shown that it is possible to produce a flame that is both strong and soot-free, using a method involving exchange of nitrogen from the oxidizer stream to the fuel stream. This approach, which is of significant fundamental interest, is also of practical importance, but a lack of sufficient fundamental understanding limits our ability to fully exploit this promising technology. For example, it is not known whether the effect of nitrogen-exchange is due to a change in the direction of convection across the flame or to a change in the detailed structure of the flame. These issues are being resolved by studying the flames under controlled conditions, where the direction of convection at the flame front can be reversed at constant stoichiometric mixture fraction.

REU Project: Effects of Nitrogen Exchange on Soot Inception and Flame Extinction Under Turbulent Conditions

An undergraduate researcher will perform experiments studying the effects of nitrogen exchange on soot inception and flame extinction. Experiments will involve gaseous hydrocarbons burning in a turbulent jet diffusion flame. Soot inception and flame extinction limits will be obtained as functions of stoichiometric mixture fraction and flame temperature. The experimental investigation will be supported by extensive analytical and computational modeling. This project will involve interaction with researchers at the NASA Glenn Research Center.

Particulate Formation and Growth Dynamics in Combustion Environments (Pratim Biswas)

Combustion systems are used extensively in many industrial processes and are a primary method of energy generation. However, the combustion of fossil fuels also results in the formation of several air pollutants whose emissions need to be controlled. A rigorous understanding of the combustion process will enable the design and operation of combustion systems to minimize the formation and control the emission of unwanted byproducts. One of the major pollutants of concern are particles, and significant research is currently underway in this field. Our research efforts have focused on developing an understanding of the combustion process to gain insights into the mechanisms of particle formation and growth, especially the toxic trace species that are difficult to capture in conventional control devices. This fundamental understanding has enabled us to develop successful control strategies for a variety of toxic metallic species. Furthermore, the understanding has also been used to propose innovative methods for converting some of these unwanted emissions to products of value, such as ferroelectric and magnetic oxides. Combustion processes are also an effective way to manufacture nanoparticles on a large scale.

REU Project #1: Transformation of Trace Species in Controlled Combustion Environments: Particle Formation and Growth Dynamics

The fate of trace species in a high temperature environment will be investigated. An undergraduate researcher will assemble and operate a furnace reactor system capable of feeding trace species and measuring representative aerosol size distributions at different residence times and temperatures. The student will measure the size distributions of nanometer and submicrometer particles based on electrical mobility, and analyze the data using the general dynamic equation to predict the evolution of the aerosol size distribution. The limitations of current theories and the use of molecular techniques for studying nucleation processes will be investigated.

REU Project #2: Use of Flame Reactors for Synthesis of Nanoparticles: Pristine and Doped Semiconductors for Use in Photocatalytic Environmental Technologies (Hydrogen Production)

Another potential project involves the use of flame reactors for synthesis of nanoparticles, especially semiconductors that can be used in photocatalytic environmental technologies. The undergraduate researcher will synthesize nanostructured titanium dioxide using diffusion and pre-mixed flame aerosol reactors. Fundamental principles of the combustion process will be used to design flame reactors to synthesize nanoparticles from gas-phase precursors. In situ light scattering will be used to characterize the evolution of particle size and morphology, and dynamic light scattering will be used to map out nanoparticle sizes. Particle formation processes will be analyzed by data inversion. Systems for effective capture of particles using electrical fields will be studied. The student will study particle formation using molecular simulation methods based on aerosol dynamic mechanisms.

Carbon Nanotubes for Environmental Applications (Richard L. Axelbaum and Pratim Biswas)

A carbon nanotube is a novel form of carbon that can be described as a monolayer of graphite rolled into a tube. Carbon nanotubes (CNTs) are finding applications from field emission displays to hydrogen storage. Present approaches to synthesizing CNTs are not efficient and they are cost prohibitive. Furthermore, the growth mechanism are not well understood, although it is well recognized that metal catalyst nanoparticles are essential for promoting growth. By employing differential mobility analyzers (DMAs), we will be able to control the particle size and thus study the effects of particle size on CNT growth. Under this program, which is funded by EPA, the nanotubes will be used in various environmental applications.

REU Project: Effects of particle size on Carbon Nanotube growth

The student will perform experiments with a DMA and a furnace reactor to studying the effects of size and composition of the catalyst particles on growth and morphology of carbon nanotubes. Experiments will involve controlling flows and temperatures as well as monitoring and controlling particle size with the DMA. Some scanning electron microscope work may also be warranted.

Nanoparticle Separation and Filtration (Da-Ren Chen)

Particulate filtration using filtration media plays an important role in industrial hygiene for the protection of workers in working places. With the increase of the usage of advanced technologies, especially for Nanotechnology, workers are often exposed to environments in which ultrafine particles will be generated in the processes of manufacture, material synthesis and material property improvement. For example, thin film coating processes for having better material thermal resistance, reducing the material corrosion or increasing the material surface hardness usually involve the evaporation and condensation of special metals or alloys. Particles produced from these processes are normally in the nanometer size range. In order to protect workers in these working places, removal of these nanometer particles by filtration becomes an important issue. Meanwhile, recent evidence shows that nanometer particles could cause more damage to human body. It is well known that inhaled particles in submicron size range can easily penetrate through extrathoracic and tracheobronchial regions of human lung and deposit on the lung wall in the alveolar region (due to very low air velocity, long residence of particles and small alveolar sacs). For particles depositing in the alveolar region, the clearance process takes place by the scavenging and engulfment of particles by free alveolar macrophage cells. Once engulfed by free alveolar macrophages, they will be carried towards the mucocillary escalator by chemotaxis, on to the gastrointestinal tract, and eventually be removed from human lung. However, particles in the sizes of nanometer may be deposited in places where they cannot be removed by macrophage cells. The deposited particles may be accumulated there or redistributed to other parts of human body through human circulation systems. Further evidence also shows that macrophage cells are totally immobilized when exposed to nanoparticles. As a result, possible illness can be induced.

In the filtration process, it is known that particle impaction serves as the major mechanism for large particle removal while the diffusion mechanism dominates the process in small particle size range. During the transition from the impaction mechanism to diffusion one, there will be a maximal point in the penetration curve at a certain particle size. Much work has been done on the subject of maximum penetration from both experimental and theoretical aspects. Further recent experimental works have demonstrated that nanoparticles penetrate filter media due to the thermal rebounce or particle reentrainment. The result is very alarming from the viewpoint of industrial hygiene. Therefore, recent focuses of Nanoparticle Research and Technology Laboratory (supervised by Dr. Chen) on the subject of nanoparticle filtration are (1) to develop nano-aerosol generators for testing the penetration efficiency of filtration media; (2) to design and evaluate apparatuses to classify generated nanoparticles into narrow size distributions and to detect the concentration of classified nanoparticles; (3) to develop standard experimental setup and procedure to properly evaluate the performance of filter media at nanometer size range.

REU Project: Experimental Evaluation of the Filtration Performance of Filter Media for Nanoparticles

The objective of this project is to experimentally investigate the performance of existing filter media under the challenge of nanoparticles and at different operational ambient environments, i.e., temperature and relative humidity.

Characterization of Ambient Air Quality (Jay R. Turner)

The Air Quality Laboratory at Washington University (WUAQL) conducts field studies and data analysis to advance the state-of-knowledge concerning ambient air quality and its linkages to emission sources, atmospheric transport and fate, and health effects. Studies can be classified into two distinct types: measurements to quantify emissions from diffuse sources, and measurements conducted with exhaustive monitoring platforms to characterize ambient air pollutants. WUAQL research on the characterization of diffuse emission sources includes investigations of particulate matter emissions from motor vehicles, including resuspended road dust and tire wear, and biogenic emissions of isoprene from the Missouri Ozarks forest. For these studies, field measurements are coupled with modeling to estimate emission rates that can reconcile observed and model-predicted concentration fields. In addition, WUAQL is the lead group for the St. Louis-Midwest Particulate Matter Supersite Monitoring Program, a multiyear monitoring study to characterize fine particulate matter in the St. Louis airshed. Working in collaboration with five other universities and one private-sector partner, an advanced measurement strategy has been deployed to monitor fine particulate matter with high temporal resolution and chemical speciation. Finally, WUAQL is also working closely with the St. Louis Community Air Project to characterize the ambient levels and atmospheric climatology of selected air toxics compounds in the St. Louis airshed.

REU Project #1: Validation of Particulate Matter Air Quality Measurements

An undergraduate researcher will learn the operation and maintenance of selected air sampling instruments used in the Supersite Program. With the understanding gained from this “hands-on” experience, the student will then explore avenues for determining the absolute accuracy and relative precision of the resulting measurements, and for distinguishing reliable from unreliable data. Related quantities measured by independent methods will be compared and interpreted, and routine calibrations will be tested by techniques designed to challenge the underlying assumptions of the method.

REU Project #2: Interpretation of Particulate Matter Air Quality Measurements

An undergraduate researcher will explore the variations in atmospheric composition observed at the Supersite monitoring platforms. The student will integrate the time series from multiple air quality measurements with information on local meteorology, atmospheric transport, emissions source locations, and episodic pollutant releases, with the goal of developing explanatory hypotheses for recurrent and singular features in the Supersite data. Known physical relationships among the Supersite measurements will be exploited to test the physical significance of statistical associations.

REU Project #3: Validation of Gaseous Organic Air Quality Measurements

An undergraduate researcher will learn the operation and maintenance of an ultraviolet differential optical absorption spectrometer (UV-DOAS) currently deployed by WUAQL on behalf of the St. Louis Community Air Project (CAP). This open-path system provides ambient concentrations of ozone, formaldehyde, benzene and several other gaseous species at high time resolution. With the understanding gained from this “hands-on” experience, the student will then explore avenues for determining the absolute accuracy and relative precision of the resulting measurements, and for distinguishing reliable from unreliable data. Related quantities measured by independent methods will be compared and interpreted, and routine calibrations will be tested by techniques designed to challenge the underlying assumptions of the method.

Inactivation of Bacterial Spores with an X-ray Enhanced Corona Electrostatic Precipitator (Lars Angenent and Pratim Biswas)

Capture and inactivation of airborne bacteria (including spores) and viruses via electrostatic precipitators are advantageous, because such precipitators can be used as air cleaners and can be readily turned on with the flip of a switch in case of a problem related to air quality hazards due to bioterrorism or biological contamination in buildings. We have developed a novel electrostatic precipitator: a corona-soft x-ray unit that relies on multiple inactivation mechanisms to capture and destroy aerosolized material. Coronas (non-thermal plasmas) are generated by application of a high voltage to a central electrode to create a region enriched with ions (positive and negatively charged), which results in a unique gas phase chemistry that can effectively oxidize biological particles. In addition, a sufficient intensity of ultra-violet (UV) radiation is generated which is effective for inactivation of bioagents. The technology may be used for the direct capture of charged particles (e.g., bioagents) in the electrical fields and will also activate catalyst surfaces to further promote deactivation. Importantly, coronas in conjunction with soft x-ray radiation increased ion-concentrations (and thus the oxidation of biological particles) several fold, while x-rays also penetrated materials deeper than electrons.

REU Project:

As an REU fellow on this project, you will study inactivation of airborne spores from Bacillus subtilis (non-pathogenic surrogates) using our soft corona x-ray system, based on our belief that the combination of corona and soft x-ray systems can effectively capture and inactivate airborne spores.

Web-based Data Analysis Tools for Air Quality Management (Stefan Falke)

The internet, particularly the Web, continues to revolution the way scientific and engineering research is conducted. To date, most research in this field has focused on the efficient and effective exchange of data among researchers and organizations. However, advances in technologies for building web applications offer the opportunity to redefine how data is visualized and analyzed “on-the-fly”. Air quality data are available from a wide range of sources and a diverse community relies on this information, including government agencies, researchers, managers and the public. Simple applications accessible through a web browser will help the air quality community collaborate, identify and fill data gaps, develop methods for assessing air quality conditions and impacts, and present information clearly and effectively to decision-makers and the public.

REU Project:

An undergraduate researcher will design, develop and construct web applications for accessing, visualizing, and analyzing data in the areas of forest fire management and/or power plant emissions management. In particular, the student will explore new approaches for integrating and comparing data from databases that reside on multiple, independent web servers. The student will learn about web services technologies and state of the art techniques in web-based geographical information systems and science (GIS). Some prior programming experience is required for this project.

Mapping Air Pollutant Concentrations (Stefan Falke)

Environmental researchers, policy makers, and epidemiologists use maps of air quality in support of exposure assessment, pattern and trend analysis, monitoring network design. The maps are based on data from monitoring networks that collect ambient air pollutant concentrations at fixed locations. Estimates of pollutant concentrations in non-monitored areas are derived using spatial interpolation methods. A wide range of spatial interpolation methods, including geostatistics, have been applied to spatially map air quality to varying degrees of success. Methods for accurately mapping fine particulate matter concentrations are being actively pursued because of the rich data sets that have recently become available, including a multi-year record of fine particleconcentrations at over 1000 monitoring sites across the United States. Research into particulate matter mapping also explores the potential of using secondary information that is closely related to particulate matter, such as visibility measurements and satellite imagery, as “surrogates” to improve the spatial interpolation.

REU project #1: Satellite imagery as a surrogate in mapping particulate matter

The undergraduate researcher analyze the relationship between fine particulate matter and aerosol indices derived from satellite imagery, develop methods for incorporating that relationship into spatial interpolation methods, conduct statistical analyses to determine the impact satellite imagery has on the interpolation compared. The interpolation will focus on air pollutant events, such as forest fire smoke plumes, during which high particulate matter concentrations are measured. The student will become familiar with a variety of data analysis techniques and with the interpretation of satellite imagery.

REU project #2: Visibility measurements as a surrogate in mapping particulate matter

The undergraduate researcher will analyze the relationship between visibility measurements and fine particle concentrations and develop methods for incorporating that relationship into the interpolation of PM2.5 concentrations. Statistical analyses will be applied to determine the effectiveness of the visibility data in improving the spatial interpolation. The student will become familiar with a variety of data analysis techniques and the science of atmospheric visibility degradation.

Processing of Satellite Imagery for Air Quality Analysis (Rudolf Husar)

This research will focus on developing algorithms and processing satellite images for the analysis of air pollution patterns and trends. The high spatial resolution (hundreds of meters) and temporal resolution (hourly to daily) of satellite imagery provide a rich resource for studying air pollution events. Satellite images can be processed to track large scale aerosol plumes (dust, smoke) and to derive aerosol optical depth, a measure of air pollution.

REU Project:

The student will perform data processing and conduct research on the air pollution pattern analysis of satellite imagery, including GOES, MODIS, SeaWiFS, AVHRR, and TOMS and will reconcile the derived patterns with surface air quality data. The project is expected to provide the student with experience in satellite imagery, multi-spectral processing software (ENVI), programming (IDL, Visual Basic), and the physical, chemical and optical characteristics of aerosols.

Novel Processes for Wastewater Treatment (Muthanna Al-Dahhan)

REU Project #1: Evaluation of Different Configuration of Anaerobic Digesters for Animal/Farm Wastes Treatment.

In this project the performance of different reactor designs in which different reactor geometry, internals and way of mixing gas recirculation, slurry recirculation, mechanical agitation, etc. will be evaluated.

REU Project #2: Treatment of the Anaerobically Digested Animal Wastes by Micro Algae

In this project the resulting nutrients (i.e., nitrogen and phosphorous present effluent) from the anaerobic digestion process will be treated using micro algae where grown algae can be harvested and converted to high value products.

REU Project #3: Wastewater Treatment Via Catalytic Wet Oxidation.

In this project the concentrated waste water are treated catalytically using a newly developed pillared clay catalyst in packed bed reactor. The performance of such catalyst using different oxidants such as air, pure oxygen, hydrogen peroxide will be studied and the needed models will be developed.

Biomass to Hydrogen (Mike Dudukovic)

Project description to follow.

Corn to Ethanol (Mike Dudukovic)

Project description to follow.

Fluorescent In-Situ Hybridization (FISH) in Anaerobic Digesters for Animal Waste (Lars Angenent)

The overall goal of the study is to investigate if an optimal upper limit of mixing exists in anaerobic digesters treating animal manure. Hence, we are monitoring the performance and microbial population dynamics as we compare mixing patterns and shear stresses between reactors. Three impeller speeds; 50, 270, and 1,700 rotations per minute (rpm) are used to create different shear rates. Computer automated radioactive particle tracking (CARPT) will be conducted to measure the flow field, instantaneous and time-averaged velocities, and turbulent parameters of the tracked phase. This technique is based on tracking the motion of a single radioactive particle as a marker of a typical element of the phase whose velocity field is to be mapped. Finally, membrane hybridization and fluorescent in situ hybridization (FISH) techniques are performed to track changes in the microbial community and structure to determine if there was any impact on the community due to the difference in shear rates. With a combination of these techniques we may, for the first time, be able to quantify mixing intensities and microbial populations and determine experimentally the link between syntrophic relationships and reactor performance.

REU Project:

As an REU fellow on this project, you will be performing FISH to investigate whether the increased shear rates in the digester causes the small flocs of microorganisms to be broken and the syntrophic relationships between bacteria and archaea to be disturbed. FISH is a molecular biology technique that targets RNA in intact cells. A positive signal will lead to visualization of bacteria and archaea with an epifluoresence microscope.

Lead Mobility in Soils and Remediation of Contaminated Soils (Daniel Giammar)

Missouri is the largest lead producing state in the United States, and lead mining and smelting have resulted in the contamination of soils and sediments, and Missouri is the largest lead producing state in the United States. The mobility of lead in soils and sediments influences lead bioavailability and has implications for the quality of groundwater and surface water resources. The objectives of this research project are to characterize the nature of lead binding in soils and to examine the immobilization of lead through the addition of phosphate.

REU Project #1: Lead Adsorption to Mineral Surfaces in the Environment

Lead adsorption to naturally occurring minerals, including iron oxides and clay minerals, can affect its mobility in contaminated soils and sediments. Work in this project will investigate the adsorption of lead onto different mineral surfaces at different solution compositions. Equilibrium adsorption will be determined in a series of batch experiments, and evaluation of adsorption rates will be determined in flow-through experiments using packed columns.

REU Project #2: Rates and Mechanisms of Lead Phosphate Dissolution and Precipitation

One potential project will investigate the dissolution and precipitation of lead phosphates. Lead phosphates are relatively insoluble solids, and consequently the addition of phosphates to contaminated soils has been proposed as an in situ immobilization remediation technique. The interpretation of the performance and long-term stability of remediated soils will benefit from additional information on rates and mechanisms of precipitation and dissolution reactions. The project will involve laboratory experiments and will include the analysis of solution chemistry and characterization of solid phases.

Heavy Metal Capture in Coal Combustion Fly Ash Soils (Daniel Giammar)

Combustion of coal can result in the release of heavy metals to the environment. While most heavy metals are incorporated with coal combustion fly ash, mercury and other volatile elements can be released to the atmosphere with the exhaust gases. New regulations will create a need for mercury emission control technologies. Sorbent addition can be used to bind mercury to particulate matter that can subsequently be captured using existing particulate control equipment. The objectives of this research project are to evaluate the stability of mercury and other heavy metals in coal combustion fly ash with and without the addition of sorbents.

REU Project #1: Mercury Binding to Fly Ash from Full-scale Facilities

A sequential extraction procedure has been developed that can be used to determine the mechanisms of mercury immobilization in fly ash. This procedure will be applied to coal combustion fly ash materials from a variety of full-scale electricity generating facilities. The work will help establish relationships between mercury capture and facility operating conditions such as the type of feed coal and the use of sorbents.

Effects of Nutrients on Bioremediation of Crude Oil (Brian Wrenn)

Biodegradation of oil on contaminated shorelines is often limited by nutrients, especially nitrogen and phosphorus. As such, shoreline oil-spill bioremediation can be effected by providing sufficient quantities of nutrients to the shoreline. Because shorelines are open environments, where washout due to the action of waves and tides can occur, several fertilizer formulations (e.g., slow-release, oleophilic) have been developed as long-term nutrient sources. Stimulation of oil biodegradation by fertilization depends on the competition between microbial uptake and washout of nutrients from the contaminated sediments, but most research on the effects of nutrients on oil biodegradation has been performed in closed systems where the kinetic and stoichiometric effects of nutrients are difficult to distinguish. Nutrient washout from intertidal zones can be simulated in continuous-flow beach microcosms in which oil is retained by adsorption to sand particles but nutrients are removed by water flow. Experiments with these microcosms have shown that, whereas nutrient availability limits the rate of oil biodegradation early in the bioremediation process, another factor (e.g., intrinsic biodegradability or bioavailability of residual hydrocarbons) becomes limiting after a short period (2-3 weeks) of biological weathering. The goal of this research is to develop mechanistic models, based on the principals of reactive transport of nutrients, to guide spill responders in choosing efficient and effective procedures for applying nutrients and other bioremediation amendments during shoreline cleanup operations. In addition, the characteristics that should be considered in the design and selection of slow-release or oleophilic fertilizers will be determined.

REU Project #1: Measurement of Nutrient Uptake Kinetics During Crude Oil Biodegradation

An undergraduate researcher will use continuous-flow beach microcosm reactors to investigate the relationships between the rates of microbial growth, nutrient uptake, and oil mineralization as the composition of the oil changes due to biodegradation. The rates of these processes will be correlated with oil composition to identify characteristics that cause the system to switch from nutrient limitation to limitation by biodegradability or bioavailability.

REU Project #2: Effects of Slow-Release and Oleophilic Fertilizers on Oil Biodegradation

The rates of nutrient release from commercial slow-release or oleophilic fertilizers will be measured in sterile continuous-flow beach microcosms. A reactor model incorporating nutrient release, microbial uptake, and washout will be developed to predict oil mineralization rate. The model predictions will be tested in biologically active microcosms.

Bioremediation of Chlorinated Aliphatic Hydrocarbons in Vegetable-Oil Barriers (Brian Wrenn)

Chlorinated aliphatic hydrocarbons (CAHs), such as trichloroethene (TCE) and chloroform, are among the most common contaminants in groundwater in the United States. These compounds have been widely used as solvents in cleaning and degreasing operations for more than fifty years, and past disposal practices have resulted in extensive contamination of groundwater. These compounds often exist in the subsurface as nonaqueous-phase liquids (NAPLs) that slowly dissolve into flowing groundwater and serve as long-term sources of groundwater contamination. CAHs can be degraded biologically under anaerobic conditions by reductive dechlorination reactions, some of which support microbial growth as primary electron-acceptor substrates (similar to the way humans use oxygen). Construction of passive in situ barriers to the subsurface transport of CAHs is becoming increasingly common, and biological reductive dechlorination is an important mechanism through which these barriers function. Due to its low cost and long-term stability in the subsurface, vegetable oil is a popular electron-donor substrate used in the construction of these passive biological barriers. Unfortunately, the mechanism through which vegetable oil functions in this application is not well understood. The purpose of this research will be to investigate the effects of vegetable oil on the transport of chlorinated solvents in porous media using bench-scale biological reactors.