Fall 2009 EWRE Seminar Series
Thursday, November 12, 2009
3:30 PM ECJ 1.204
Dr. JiHyang Kweon
Associate Professor
Department of Environmental Engineering
Konkuk University, Korea
Effects of flocs on the foulding in coagulation-member processes
Coagulation is one of the most frequently applied pretreatment processes to mitigate fouling of microfilters used for drinking water purification. When immersed or inline coagulation is installed as a pretreatment, flocs are removed by MF but could also act as foulants of MF. An attempt was made to investigate the effects of flocs formed in raw waters with different physical/chemical characteristics on the fouling of MF. Several floc properties such as size distributions and structural fractal dimensions were analyzed. The compressibility and specific resistances of cake layers by flocs on the membrane surface were also measured. Severe rainfalls during summer seasons in Korea substantially increased the amount of particles in the raw water. Coagulation pretreatment improved the water production, regardless of whether a settling process was applied, compared to direct application of raw water onto the membranes. However, the flux decline of pretreated water was greater when settling was not applied. Floc properties strongly influenced characteristics of cake layers on the microfiltration. Coagulated flocs from a high turbidity water could decrease water production through microfiltration, especially when NOM concentration is significant.
Dr. JiHyeon Song
Associate Professor
Civil & Environmental Engineering
Sejong University, Korea
Bioelectrical and Electrochemical Treatments of Odorous Compounds and Precursors in Sewer Systems
Odor emissions from domestic sewer systems including manholes and lift stations cause public complaints especially in big cities, and these problems are not easy to handle because not only are the odor sources scattered in many areas but also the odor concentration and flux vary greatly. Sediment organic matters (SOMs) deposited at the bottom of the sewer facilities are known to be the precursors of malodorous compounds when the oxidoreduction potential (ORP) drops and anaerobic conditions are formed. To reduce the odor problems from the non-point sources, a combined treatment method, consisting of (1) a bioelectrical, electricity-generating reaction and (2) an electrochemical, power-consuming oxidation, has been proposed and investigated. First, an electrical circuit was implemented in a lab-scale container by embedding a graphite electrode (anode) in anaerobic sediment and connecting it to another electrode (cathode) in the overlying aerobic water. Under current generating conditions, electrically active bacteria utilized SOMs as substrates and oxidized other odor precursors. The ORP near the anode surface increased substantially and the production of hydrogen sulfide decreased. Second, an electrochemical oxidation unit, where a direct current was applied using a power supply to an IrO2/Ti anode and a stainless steel cathode submerged into sediment slurry, was implemented to further eliminate the odor production potential and odor itself. Oxidants produced on the surface of the anode increased the ORP and actively destroyed SOMs and odor-causing compounds from the sediment. Overall, the bioelectrical approach can be used as a biosensor using the current continuously generated, and the electrochemical oxidation can be an effective method to simultaneously reduce odor compounds and SOMs directly from the sewer systems.
Thursday, November 5, 2009
3:30 PM ECJ 1.204
Patrick Sejkora
B.S. Villanova, 2008
Impact and Mitigation of Bacteria Associated with Highway Bridges
Bridges adjacent to surface water can provide habitat for birds and bats. It has been postulated that feces from these populations can increase the downstream fecal indicator bacteria concentrations. Bull Creek in Austin, Texas is a stream that is crossed several times by state highways. Between March and July, the bridges’ undersides are inhabited by cliff swallows. This phenomenon allows for direct deposition of feces into the surface water. We sampled Bull Creek upstream and downstream of a bridge throughout the year; our data demonstrate downstream concentrations of Escherichia coli exceeding 2000 most probable number (MPN) per 100 mL while the birds are rearing nestlings. However, when the nestlings have fledged, the bird population becomes more scattered, and bacteria concentrations return to near the background level of 40 MPN/100 mL. Although brief, the augmented bacterial loading of the creek during the nesting period exceeds contact recreation surface water quality standards.
Allison Osborne
B.S. University of North Carolina, 2007
Green Goo: harvesting microalgae for biofuel
Global dependence on liquid fuels despite decreasing oil reserves and increasing fuel prices has become an issue of imminent concern, especially as suitable alternatives have yet to be found. While some biofuel feedstocks have proven unsuitable and unsustainable due to their high production energy requirements, co-use as food crops, and associated greenhouse gas emissions; the diversity and productivity of microalgae may provide the solution for future fuel needs. However, the industry of algae cultivation for oil production is inexperienced and the optimum conditions and processes for cost-effective production have yet to be identified. In particular, harvesting methods for concentrating dilute solutions of microalgae into a concentrated sludge that can be further processed may be the greatest challenge. This research investigates several harvesting methods, including traditional chemical coagulation and flocculation, autoflocculation, electrolytic coagulation, and dissolved air flotation, and evaluates their efficiency, cost-effectiveness, and drawbacks. In addition, it addresses the experiences of pilot scale implementation of autoflocculation and integration with subsequent processing.
Thursday, October 22, 2009
3:30 PM ECJ 1.204
Elliott Gall
B.S., University of Florida 2006 (Environmental Engineering)
Primary and Secondary Emissions from Green Building Materials: Large Chamber Experiments
Indoor sources of air pollution represent a large portion of overall human exposure to air toxics, due to human proximity and the temporal dominance of the indoor environment. However it has been posited that indoor chemistry drives pollutant transformation to an extent that indoor reactions, resulting in secondary emissions, must be considered. In the indoor environment, ozone is often the driver of interfacial chemistry, and there have been numerous laboratory studies characterizing ozone removal to building surfaces. However, little is known or considered regarding ozone removal and secondary emissions from green and sustainable building materials. To determine the impact of ozone on the indoor air quality characteristics of three green building materials, experiments were conducted with recycled carpet, eurostone ceiling tile and low-VOC paint and primer on recycled drywall to determine: 1) heavy aldehyde primary emission rates, 2) ozone deposition velocity, and 3) heavy aldehyde secondary emission rates. The availability of this information is highly valuable to building designers and the United States Green Building Council, who can incorporate accommodations to materials testing and ranking protocols to address secondary emissions.
Yamuna Pathmanathan
BS in Civil Engineering, University of Peradeniya, Sri Lanka (2005)
Particles in Stormwater
Urban stormwater contains a high concentration of particles and a number of hazardous constituents, such as heavy metals and polycyclic aromatic hydrocarbons (PAH). These pollutants are associated with the solids to a considerable extent and can therefore be removed from the stormwater through sedimentation and particle and filtration. Due to this fact, sedimentation filters have frequently been used as a method for the treatment of stormwater. Information regarding particle characteristics and associated pollutants in stormwater is therefore of great importance to engineers involved in the design of particle removial devices for urban stormwater, and the development of "Best Management Practices." This study investigates both the influent and effluent particle characteristics (such as particle size distribution and suspended sediment concentration) of stormwater filters in two different settings. First, the effectiveness of an existing stormwater sedimentation filter in the City of Austin (COA) in treating the water from a few recent storm events was measured with a few different particle counters. Second, the effectiveness of different filter designs that include biofiltration was measured using a synthetic stormwater and small filter columns at the Center for Research in Water Resources; this latter work has been undertaken for the City of Austin because they are considering changing the specifications for stormwater filters throughout the City.
Thursday, October 15, 2009
3:30 PM ECJ 1.204
Allen Burton, Ph.D.
Dr. Burton is the Director of NOAA's Cooperative Institute of Limnology and Ecosystem Research and a Professor in the School of Natural Resources and Environment at the University of Michigan.
University of Texas at Dallas, M.S. 1980, Ph.D. 1984. (Environmental Science)
Auburn University, M.S. 1978. (Microbiology)
Ouachita Baptist University, B.S. 1976. (Biology and Chemistry)
Assessing Aquatic Ecosystems: Small Streams to Great Lakes
It is recognized that assessments of aquatic ecosystem impairment and risk are typically crude with high levels of uncertainty. The USEPA Science Advisory Board recently highlighted the need for more accurate characterizations and linkages of exposure and effects. This is best done using multiple lines-of-evidence that tie spatial and temporal exposure dynamics to receptor effects. A variety of examples will be presented showing recent integrated assessments of physical, chemical and biological stressors in a range of aquatic ecosystems that improve the risk characterization process, the ranking of stressors, and forecasting of impeding habitat and climate change impacts.
Thursday, October 1, 2009
3:30 PM ECJ 1.204
Eric Hersh
B.S. Civil Engineering, Tufts University
M.S. Environmental and Water Resources Engineering, UT-Austin
Despite the ever-present dual threat of vicious polar bears and melting ice caps, a project was conducted in the Chukchi and Beaufort Seas (off the west and north coasts of Alaska) to conduct a baseline assessment of the continental shelf ecosystem. Particular focus was on ship-based physical, chemical, and biological sampling of the benthos and on the development of a workable food web model. This talk will intersperse examples of real-time, dynamic GIS and data management with numerous photos and tales of derring-do.
Thursday, September 24, 2009
3:30 PM ECJ 1.204
Lauren Greenlee
BS in Chemical Engineering, University of Michigan-Ann Arbor (2001)
MS in Environmental and Water Resources Engineering, University of Texas-Austin (2006)
PhD in Chemical Engineering, University of Texas-Austin (2009
Enhancing Recovery of Reverse Osmosis Desalination: Side-stream Oxidation of Antiscalants to Precipitate Salts
The United States has many inland regions with untapped brackish water (500–10,000 mg/L total dissolved solids) resources. Reverse osmosis (RO) membrane desalination is a feasible solution, but the product recovery (volume of product water per volume of feed water) range is only 65 – 90%; i.e., at least 10% of the feed water becomes the RO waste stream, or concentrate. The costs and technical feasibility of concentrate disposal severely limit the application of inland RO. In brackish water RO systems, recovery is limited by salt precipitation. Chemicals called antiscalants are used to complex with problematic salts (CaCO3, CaSO4, BaSO4, SrSO4, silica), delaying precipitation. However, salt concentration increases with recovery, and eventually precipitation control is overcome. To increase system recovery and decrease the concentrate volume, a new approach is required. This research has focused on the development of a novel three-stage process to treat the concentrate from a brackish water RO system. The process achieves problematic salt removal through (I) antiscalant deactivation, (II) precipitation, and (III) solid/liquid separation. Antiscalant deactivation is performed using ozone (O3) and hydrogen peroxide (H2O2). pH elevation is used to precipitate salts, and solid/liquid separation is achieved through filtration. Results show that the treatment process allows removal of a significant portion (>80%) of the calcium present in the RO concentrate.
Thursday,September 17, 2009
3:30 PM ECJ 1.204
Katherine Alfredo
B.Eng. The Cooper Union for the Advance Placement of Science and Art (2005)
M.S. in Environmental Engineering from UT at Austin (2008)
U.S. Student Fulbright Fellow 2008-2009
The presence of fluoride ions in drinking water can occur naturally, as contamination from a byproduct of manufacturing, or as a water treatment plant additive. Fluoride is thought to have an optimal concentration in the range of 0.7 to 1.2 mg/L, with health (bone and
tooth) problems associated with both higher and lower levels.
Elevated levels of naturally occurring fluoride in the Bongo District of northeastern Ghana has resulted in the “capping� of many hand pump wells, rendering them unusable and leaving many without access to safe drinking water. An effective treatment system cannot be engineered until the dynamic boundaries between the treatment technology, the natural environment, and the local culture are understood. In researching feasible defluoridation solutions for a rural community such as Bongo, questions of the extent and nature of the fluoride contamination, community water usage patterns, and cultural and environmental constraints to treatment process design are important.
The seminar will address these questions in light of my experiences in Bongo in the last year.
Thursday,September 10, 2009
3:30 PM ECJ 1.204
Dr. Danny Reible
Bettie Margaret Smith Chair in Environmental Health Engineering
Ph.D., California Institute of Technology, Pasadena, California, Chemical Engineering, 1982
M.S., California Institute of Technology, Pasadena, California, Chemical Engineering, 1979
B.S., Lamar University, Beaumont, Texas, Chemical Engineering, 1977
Laboratory Safety Seminar
Thursday,September 3, 2009
3:30 PM ECJ 1.204
Dr. Ying Xu
PhD, Virginia Tech
M.E., Tsinghua University, 2004
B.E., Tsinghua University, 2001
Emissions of Phthalate Plasticizer from Polymeric Building Materials
Modern indoor environments contain a vast array of contaminating sources. Emissions from these sources produce contaminant concentrations that are substantially higher indoors than outside. Because we spend most of our time indoors, exposure to indoor pollutants may be orders-of-magnitude greater than that experienced outdoors. Phthalate esters have been recognized as major indoor pollutants. They are mainly used as plasticizers to enhance the flexibility of polyvinylchloride (PVC) products, as well as in humectants, emollients, and antifoaming agents. Phthalates are found in a wide range of consumer products including floor and wall coverings, car interior trim, floor tiles, gloves, footwear, insulation on wiring, and artificial leather. Because these phthalate additives are not chemically bound to the polymer matrix, slow emission from the products to the surrounding air or other media usually occurs.
Biomonitoring data suggest that over 75% of the U.S. population is exposed to phthalates. The ubiquitous exposure to phthalates is of concern because toxicological investigations have demonstrated considerable adverse health effects of phthalates and their metabolites. Studies have shown that exposure to phthalates results in profound and irreversible changes in the development of the reproductive tract, especially in males, raising the possibility that phthalate exposures could be the leading cause of reproductive disorders in humans. In addition, effects such as increases in prenatal mortality, reduced growth and birth weight, skeletal, visceral, and external malformations are possibly associated with phthalate exposure. Epidemiologic studies in children also show associations between phthalate exposure in the home and the risk of asthma and allergies.
Given the ubiquitous nature of phthalates in the environment and the potential for adverse human health impacts, there is a critical need to understand indoor emissions of phthalates and to identify the most important sources and pathways of exposure. In this study, a model that integrates the fundamental mechanisms governing emissions of semi-volatile organic compounds (SVOCs) from polymeric materials and their subsequent interaction with indoor surfaces and airborne particles was developed. The emissions model is consistent with analogous mechanistic models that predict emission of volatile organic compounds (VOCs) from building materials. Reasonable agreement between model predictions and gas-phase di-2-ethylhexyl phthalate (DEHP) concentrations was achieved for data collected in a previously published experimental study that measured emissions of DEHP from vinyl flooring in two very different chambers. The analysis showed that while emissions of highly volatile VOCs are subject to “internal� control (through the material-phase diffusion coefficient), emissions of the very low volatility SVOCs are subject to “external� control (through partitioning into the gas phase, the convective mass transfer coefficient, and adsorption onto interior surfaces).
Because of the difficulties associated with sampling and analysis of SVOCs, only a few chamber studies quantifying their emissions from building materials and consumer products are available. To more rigorously validate the SVOCs emission model and more completely understand the mechanisms governing the release of phthalate from polymeric building materials, the emission of DEHP from vinyl flooring was studied for up to 140 days in a specially-designed stainless steel chamber. In the duplicate chamber study, the gas-phase concentration in the chamber increased slowly and reached a steady state level of 0.9 µg/m3 after 30 days. By increasing the area of vinyl flooring and decreasing that of the stainless steel surface in the chamber, the time to reach steady state was significantly reduced, compared to the previous study (1 month vs. 5 months). The adsorption isotherm of DEHP on the interior stainless steel chamber surface was explicitly measured using two different methods (solvent extraction and thermal desorption). Strong adsorption of DEHP onto the stainless steel surface was observed and found to follow a simple linear relationship. In addition, parameters measured in the experiments were then applied in the fundamental SVOCs emission model. Good agreement was obtained between the predictions of the model and the gas-phase DEHP chamber concentrations, without resorting to fitting of model parameters.
These chamber studies have shown that the tendency of SVOCs to adsorb strongly to interior surfaces has a very strong influence on the emission rate. Compared to the experimental chamber systems, however, the real indoor environment has many other types of surface that will adsorb phthalates to different extents. The emission rate measured in a test chamber may therefore be quite different to the emission rate from the same material in the indoor environment. For this reason, both a two-room model and a more representative three-compartment model were developed successively to estimate the emission rate of DEHP from vinyl flooring, the evolving gas-phase and adsorbed surface concentrations, and human exposures (via inhalation, dermal absorption and oral ingestion of dust) in a realistic indoor environment. Adsorption isotherms for phthalates and plasticizers on interior surfaces, such as carpet, wood, dust and human skin, were derived from previous field and laboratory studies. A subsequent sensitivity analysis revealed that the vinyl flooring source characteristics, as well as mass-transfer coefficients and ventilation rates, are important variables influencing the steady-state DEHP concentration and resulting exposures. A simple uncertainty analysis suggested that residential exposure to DEHP originating from vinyl flooring may fall somewhere between about 5 µg/kg/d and 180 µg/kg/d. The roughly 40-fold range in exposure reveals the inherent difficulty in using biomonitoring results to identify specific sources of exposure in the general population.
This research represents the first attempt to explicitly elucidate the fundamental mechanisms governing the release of phthalates from polymeric building materials as well as their subsequent interaction with interior surfaces. The mechanistic models developed can most likely be extended to predict concentration and exposure arising from other sources of phthalates, other sources of other semi-volatile organic compounds (such as biocides and flame retardants), as well as emissions into other environmental media (food, water, saliva, and even blood). The results will be of value to architects, governments, manufacturers, and engineers who wish to specify low-emitting green materials for healthy buildings. It will permit health professionals to identify and control health risks associated with many of the SVOCs used in indoor materials and consumer products in a relatively inexpensive way.
Spring 2009 EWRE Seminar Series
Spring 2008 EWRE Seminar Series
Fall 2007 EWRE Seminar Series
