VTechWorks Repository :: Browsing by Author "Gallagher, Daniel L."

Browsing by Author "Gallagher, Daniel L."

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Advancing Potable Water Infrastructure through an Improved Understanding of Polymer Pipe Oxidation, Polymer–Contaminant Interactions, and Consumer Perception of Taste
Whelton, Andrew James (Virginia Tech, 2009-04-02)
While more than 100 years of research has focused on removing acute and chronic health threats from water, substantially less study has focused on potable water infrastructure and water quality deterioration, monitoring technologies, and relationships between water taste and consumer health. These knowledge–gaps have left infrastructure users, owners, regulators, and public health professionals largely unaware of how premise and buried polymer water pipes deteriorate and sorb/ desorb organic contaminants during normal operations and following water contamination events. These knowledge–gaps also prevent infrastructure managers from producing drinking water that optimizes mineral content for both water taste and health benefits, and employing a monitoring tool capable of immediately detecting water contamination or equipment failures. Research was conducted to address these challenges using analytical chemistry, environmental engineering, food science, polymer chemistry, public health, and material science principles. This work was enhanced by collaborations with sixteen American water utilities and the National Institute for Standards and Technology. These efforts were funded by the National Science Foundation, American Water Works Association, and the Water Research Foundation. Research results are unique and provide important scientific contributions to the public health, potable water, and material science industries. Particular achievements include the: (1) Evaluation of linkages between minerals, water palatability, and health useful for water production and public health decisions; (2) Creation of a novel infrastructure and water quality surveillance tool that has begun water utility implementation in the USA; (3) Development of an accelerated chlorinated water aging method with stable water pH, free chlorine, and alkalinity concentration that enables interpretation of polymer pipe surface and bulk characteristic changes; (4) Discovery that polar compounds are 2–193% more soluble in PEX than HDPE water pipes; (5) Finding that several polymer and contaminant properties can be used to predict contaminant diffusivity and solubility during sorption and desorption in new, lab aged, and water utility PE pipes; and the (6) Discovery that chlorinated water exposure of HDPE and PEX pipes increases polar contaminant diffusivity during sorption by 50–162% and decreases diffusivity during desorption as much as 211%. Outcomes of this work have domestic and global significance, and if engaged, can greatly improve public health protection, potable water infrastructure operations, water quality, sustainability, and regulation.
Aging and Copper Corrosion By-Product Release: Role of Common Anions, Impact of Silica and Chlorine, and Mitigating Release in New Pipe
Powers, Kimberly Alice (Virginia Tech, 2000-12-15)
It is desirable to reduce leaching of copper from home plumbing because of environmental concerns and to comply with stringent regulation of copper in wastewater and drinking water. The solubility of the scale (oxidized copper rust layer) on the copper pipe wall, which directly contacts drinking water, is a key factor controlling the maximum soluble copper release. Gradual replacement of soluble Cu(OH)2 scale to less soluble scale is desirable and occurs through a process known as "aging. The presence of sulfate, bicarbonate and orthophosphate in water can quickly convert Cu(OH)2 to less soluble solids. In some cases, this produces a desirable short-term reduction in copper solubility, but over longer time periods formation of these solids can be detrimental because they interfere with formation of very low solubility tenorite (CuO)or malachite phases. Likewise, silica present in water can sorb to Cu(OH)2 and hinder aging to low solubility tenorite, while the presence of chlorine can hasten aging by a chemical reaction with cupric species that has never been previously observed in the drinking water field. Mild chemical treatments that might be used to accelerate aging, and which could be applied to reduce environmental impacts of newly installed copper pipe, were successfully tested. Chemical pretreatments using lime, caustic, soda ash or chlorine reduced copper release by as much as 84% compared to new pipes without pretreatment.
Air Pollution Distribution under an Elevated Train Station (A Case Study of Silom Station in Downtown Bangkok)
Charusombat, Umarporn (Virginia Tech, 1998-12-14)
To solve traffic congestion in Bangkok, the Bangkok Mass Transit system (BTS) constructed an overhead rail system with 24 stations. The BTS train station, S2, in this study area covers Silom road and obstructs the air pollutant dispersion in a congestion area. The 1: 200 physical model of the buildings along Silom road with the train station, S2, was simulated in this research to determine the air pollutant dispersion in the train station area. A tracer gas (CO₂) was emitted from a simulated line source with emission rates of 0.383, 0.681, 1.293, 2.586, 5.177 and 10.77 mg/min to simulate actual pollutant emission rates. The CO₂ gas was sampled at 55 locations in the model. The Kriging method was used to interpolate the data in the study area. . Emission rates were used to make the difference between measured CO₂ in the model area and ambient CO₂ large enough to be differentiated. Regression Analysis was used to relate analytically the mass emission rate to the CO₂ concentration. The results indicate that the maximum CO concentrations exceed the 30 ppm Bangkok standard along the Southeast side of Silom Road at the passenger platform level. Drivers will acquire more harmful levels of CO than pedestrians at street level, especially near the Southwest end of the train station. NO₂ concentrations do not exceed the standard (0.17 ppm) at street level. The highest predicted VOC is 1.05 ppm. These results may be used in the future for numerical modeling study.
Analysis of Organic and Inorganic Parameters in Southern Virginia Rivers Following a Coal ash Spill
Waggener, Keegan Edward (Virginia Tech, 2018-01-23)
In February 2014, a coal ash spill on Duke Energy's Dan River Plant in Eden, NC released approximately 39,000 tons of coal ash into the Dan River. It took approximately one week to stop the spill. Starting in February 2015, drinking water utilities using the Dan River experienced a series of taste and odor (TandO) events described as "earthy" or "musty". Similar TandO events were not documented before the coal ash spill. This research attempted to understand causes of the TandO events and if the coal ash spill was connected. A variety of water quality analyses were performed on twelve sites from August 2016 to September 2017 on the Dan and Smith Rivers. The Smith River served as the control. From concentrations of coal ash indicators (particularly Ba, Sr, As, V, and Br-), there was a signature of coal ash on the Dan River that was not present on the Smith River. The signature could not be attributed to the coal ash spill, as the signature was present upstream of the spill. Chronic ecosystem toxicity due to metals was low and not significantly different between the Dan and Smith Rivers. No substantial TandO events occurred during the period of this study. All monitored odorants were detected with varying frequencies in both the Dan and Smith Rivers. No significant change in odorant concentration was found above and below the location of the coal ash spill.
Application of a Mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME)
Moore, Tim Orland II (Virginia Tech, 2009-09-08)
According to the World Health Organization, urban air pollution is a high public health priority due its linkage to cardio-pulmonary disease and association with increased mortality and morbidity (1, 2). Additionally, air pollution impacts climate change, visibility, and ecosystem health. The development of effective strategies for improving air quality requires accurate estimates of air pollutant emissions. In response to the need for new approaches to measuring emissions, we have designed a mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME) that applies a proven, science-based method known as eddy covariance for the direct quantification of anthropogenic emissions to the atmosphere. The mobile flux lab is a tool with novel, multifaceted abilities to assess air quality and improve the fidelity of emission inventories. Measurements of air pollutant concentrations in multiple locations at the neighborhood scale can provide much greater spatial resolution for population exposure assessments. The lab's mobility allows it to target specific sources, and plumes from these can be analyzed to determine emission factors. Through eddy covariance, the lab provides the new ability to directly measure emissions of a suite of air pollutants. We have deployed the FLAME to three different settings: a rural Appalachian town where coal transport is the dominant industry; schools in the medium-sized city of Roanoke, Virginia; and the large urban areas around Norfolk, Virginia, to measure neighborhood-scale emissions of air pollution. These areas routinely experience high ozone and particulate matter concentrations and include a diverse array of residential neighborhoods and industries. The FLAME is able to capture emissions from all ground-based sources, such as motor vehicles, rail and barge traffic, refuse fires and refueling stations, for which no direct measurement method has been available previously. Experiments focus on carbon dioxide (CO₂), the principal greenhouse gas responsible for climate change; nitrogen oxides (NOx), a key ingredient in ground-level ozone and acid rain; volatile organic compounds (VOCs), a second key ingredient in ozone and many of which are air toxics; and fine particulate matter (PM2.5), a cause of mortality, decreased visibility, and climate change. This research provides some of the first measurements of neighborhood-scale anthropogenic emissions of CO₂, NOx, VOCs and PM2.5 and as a result, the first opportunity to validate official emission inventories directly. The results indicate that a mobile eddy covariance system can be used successfully to measure fluxes of multiple pollutants in a variety of urban settings. With certain pollutants in certain locations, flux measurements confirmed inventories, but in others, they disagreed by factors of up to five, suggesting that parts of the inventory may be severely over- or underestimated. Over the scale of a few kilometers within a city, emissions were highly heterogeneous in both space and time. FLAME-based measurements also confirmed published emission factors from coal barges and showed that idling vehicles are the dominant source of emissions of air toxics around seven schools in southwest Virginia. Measurements from this study corroborate existing emission inventories of CO₂ and NOx and suggest that inventories of PM2.5 may be overestimated. Despite the tremendous spatial and temporal variability in emissions found in dense urban areas, CO₂ fluxes on average are very similar across the areas in this study and other urban areas in the developed world. Nevertheless, the high level of variability in spatial and temporal patterns of emissions presents a challenge to air quality modelers. The finding that emissions from idling vehicles at schools are likely responsible for creating hot spots of air toxics adds to the urgency of implementing no-idling and other rules to reduce the exposure of children to such pollutants. Ultimately, the results of this study can be used in combination with knowledge from existing emission inventories to improve the science and policies surrounding air pollution.
Application of Automated Facial Expression Analysis and Facial Action Coding System to Assess Affective Response to Consumer Products
Clark, Elizabeth A. (Virginia Tech, 2020-03-17)
Sensory and consumer sciences seek to comprehend the influences of sensory perception on consumer behaviors such as product liking and purchase. The food industry assesses product liking through hedonic testing but often does not capture affectual response as it pertains to product-generated (PG) and product-associated (PA) emotions. This research sought to assess the application of PA and PG emotion methodology to better understand consumer experiences. A systematic review of the existing literature was performed that focused on the Facial Action Coding System (FACS) and its use to investigate consumer affect and characterize human emotional response to product-based stimuli, which revealed inconsistencies in how FACS is carried out as well as how emotional response is inferred from Action Unit (AU) activation. Automatic Facial Expression Analysis (AFEA), which automates FACS and translates the facial muscular positioning into the basic universal emotions, was then used in a two-part study. In the first study (n=50 participants), AFEA, a Check-All-That-Apply (CATA) emotions questionnaire, and a Single-Target Implicit Association Test (ST-IAT) were used to characterize the relationship between PA as well as PG emotions and consumer behavior (acceptability, purchase intent) towards milk in various types of packaging (k=6). The ST-IAT did not yield significant PA emotions for packaged milk (p>0.05), but correspondence analysis of CATA data produced PA emotion insights including term selection based on arousal and underlying approach/withdrawal motivation related to packaging pigmentation. Time series statistical analysis of AFEA data provided increased insights on significant emotion expression, but the lack of difference (p>0.05) between certain expressed emotions that maintain no related AUs, such as happy and disgust, indicates that AFEA software may not be identifying AUs and determining emotion-based inferences in agreement with FACS. In the second study, AFEA data from the sensory evaluation (n=48 participants) of light-exposed milk stimuli (k=4) stored in packaging with various light-blocking properties) underwent time series statistical analysis to determine if the sensory-engaging nature of control stimuli could impact time series statistical analysis of AFEA data. When compared against the limited sensory engaging (blank screen) control, contempt, happy, and angry were expressed more intensely (p<0.025) and with greater incidence for the light-exposed milk stimuli; neutral was expressed exclusively in the same manner for the blank screen. Comparatively, intense neutral expression (p<0.025) was brief, fragmented, and often accompanied by intense (albeit fleeting) expressions of happy, sad, or contempt for the sensory engaging control (water); emotions such as surprised, scared, and sad were expressed similarly for the light-exposed milk stimuli. As such, it was determined that care should be taken while comparing the control and experimental stimuli in time series analysis as facial activation of muscles/AUs related to sensory perception (e.g., chewing, smelling) can impact the resulting interpretation. Collectively, the use of PA and PG emotion methodology provided additional insights on consumer-product related behaviors. However, it is hard to conclude whether AFEA is yielding emotional interpretations based on true facial expression of emotion or facial actions related to sensory perception for consumer products such as foods and beverages.
Applications of Sensory Analysis for Water Quality Assessment
Byrd, Julia Frances (Virginia Tech, 2018-01-30)
In recent years, communities that source raw water from the Dan River experienced two severe and unprecedented outbreaks of unpleasant tastes and odors in their drinking water. During both TandO events strong 'earthy', 'musty' odors were reported, but the source was not identified. The first TandO event began in early February, 2015 and coincided with an algal bloom in the Dan River. The algal bloom was thought to be the cause, but after the bloom dissipated, odors persisted until May 2015. The second TandO in October, 2015 did not coincide with observed algal blooms. On February 2, 2014 approximately 39,000 tons of coal ash from a Duke Energy coal ash pond was spilled into the Dan River near Eden, NC. As there were no documented TandO events before the spill, there is concern the coal ash adversely impacted water quality and biological communities in the Dan River leading to the TandO events. In addition to the coal ash spill, years of industrial and agricultural activity in the Dan River area may have contributed to the TandO events. The purpose of this research was to elucidate causes of the two TandO events and provide guidance to prevent future problems. Monthly water samples were collected from August, 2016 to September, 2017 from twelve sites along the Dan and Smith Rivers. Multivariate analyses were applied to look for underlying factors, spatial or temporal trends in the data. There were no reported TandO events during the project but sensory analysis, Flavor Profile Analysis, characterized earthy/musty odors present. No temporal or spatial trends of odors were observed. Seven earthy/musty odorants commonly associated with TandO events were detected. Odor intensity was mainly driven by geosmin, but no relationship between strong odors and odorants was observed.
Assessing Human Exposure to Emissions from Ultrasonic Humidifiers
Yao, Wenchuo (Virginia Tech, 2021-09-14)
Portable ultrasonic humidifiers add moisture into room air, but they simultaneously add exposure risks of aerosolized metals from drinking water used as fill water. The inhalation exposure from emitted metals can be overlooked, and thus, co-exposure of inhalation and ingestion and co-exposure to multiple inorganic metals is investigated. The objectives of this work are: 1) predict airborne metal concentrations and particle sizes in four realistic room scenarios (33 m3 small or 72 m3 large, with varying ventilation rates from 0.2/hr -1.5/hr), and the investigated metals are arsenic, cadmium, chromium, copper, lead, and manganese; 2) characterize exposure doses and consequent risks for adults and 0.25, 1, 2.5, and 6 yr old children, when using identical drinking water ingested and as fill water, including inhalation of fine, respirable particles generated at the frequency of 8 hrs/day (equals 121.67 days/yr) and daily ingestion, under four realistic room scenarios. The risk assessment includes non-cancer [calculation of average daily dose (ADD) and hazard quotient (HQ)] and cancer risk evaluation; 3) quantify deposition fraction and deposited doses of multiple metals in human adult's and children's respiratory tract, using multi-path particle dosimetry (MPPD) model. Results show airborne-particle-bound metal concentrations increase proportionally with water metals, and a poorly ventilated room causes greater exposure. Ingestion ADDs are 2 magnitudes higher than inhalation ADD, at identical water metal concentrations and daily exposure frequency. However, in the worse-case scenario of 33 m3 small room with low air exchange rate, the consequent inhalation HQs are all greater than 1 for children and adults, except for lead, indicating significant non-cancer risks when exposed to humidifier particles under the worse-case scenario. The cancer risks for arsenic, cadmium, chromium, and lead metals reveal are greater than acceptable one case in a million population (1E-6) produced from inhalation of the humidifier emitted metal-containing particles only. The MPPD model results indicate inhaled metal-containing airborne particles deposit primarily in head and pulmonary regions, and a greater dose (unit in µg/kg body weight/day) deposits in children than adults. Inhalation of ultrasonic humidifier aerosolized metals results in additional, and potentially greater risks (indicated by HQinhalation >1, and greater deposited dose) than ingestion at the same aqueous metal concentration, especially for children. Room conditions (i.e. volume and ventilation) influence risks. Both inhalation and ingestion exposures require consideration for eliminating multiple metal exposures and health-based environmental policy making. Consumers should be aware that they may be degrading their indoor air quality by using ultrasonic humidifiers even when filling with acceptable water quality for drinking.
Assessing Various Technologies to Remediate a Hydrocarbon Contaminated Aquifer
Parcher, Mary Ann (Virginia Tech, 1999-01-13)
Releases of nonaqueous phase liquids (NAPLs) to groundwater systems are a serious and widespread problem throughout the United States. Research was conducted to determine if numerical groundwater flow and transport models could evaluate the effectiveness of alternative remedial strategies to reduce dissolved hydrocarbon contamination in aquifers, and therefore serve as tools to aid environmental managers in the remedial decision making process. A fuel distribution terminal in the Eastern United States was selected as the test site. A release of diesel and jet fuels from the terminal loading rack area contaminated the unconfined aquifer beneath the terminal and migrated off-site, impacting commercial and residential areas. In the analyses, groundwater flow and transport models were calibrated to site data. The calibrated models were applied to simulate four remedial options: (1) natural attenuation, (2) groundwater extraction, (3) groundwater flushing, and (4) microbial fences. Results of the predictive simulations indicated that the groundwater flushing remedial option provided the greatest reduction of benzene and TEX mass from the NAPL source as well as the lowest concentrations of benzene and TEX in the aquifer. The calibrated numerical models were able to predict the effectiveness of various remedial options and provide a basis for comparison. The modeling in conjunction with other factors, such as cost, were utilized to facilitate the decision making process.
Assessment of the fate of manganese in oxide-coated filtration systems
Crowe, Andrea L. (Virginia Tech, 1997-01-24)
"This study examined the fate of manganese in manganese oxide (MnO_x(s)) coated filter media. Specific objectives of the project included the following: 1. Determination of the effect of influent pH upon Mn(II) sorption and oxidation and upon the physical characteristics of the coating on the media. 2. Determination of the effect of backwash rate upon MnO_x(s) coatings. 3. Examination of the effect of air scour upon MnO_x(s) coatings. 4. Observation of the effect of an increasing MnO_x(s) coating on the physical characteristics of anthracite coal filter media. 5. Development of an overall mass balance on manganese loading and accumulation on the filter media. Resolution of the stated objectives involved construction, optimization, and continuous operation of a pilot-scale filtration system for the purpose of removing manganese from filter-applied water. The pilot-scale filter system functioned like a typical water treatment plant filtration system with similar hydraulic loading rates, influent manganese concentrations, free chlorine dosage, filter media bed depths, filter run times, and backwash rates. With regard to the fate of manganese in MnO_x(s)-coated filter media, it was determined that as long as free chlorine was present to oxidize sorbed manganese, manganese continued to accumulate and remained on the media in sufficient concentrations to promote continual removal of soluble Mn(II). While oxide coating that was susceptible to breakage was removed in backwash, some portion of coating remained on the media. The combination of MnO_x(s) accumulation during filtration and its partial removal during backwash maintained a net amount of MnO_x(s) coating optimal for catalyzing further manganese removal and, yet, did not hinder filtration for turbidity by significantly altering the size of the media. The results of the pilot-scale study also indicated the following pertinent conclusions: 1. Neutral or slightly acidic pH conditions (7 ≥ pH ≥ 6) inhibited Mn(11) oxidation before filtration and, instead, promoted sorption and oxidation of Mn(II) on MnO_x(s)-coated media. Alkaline filter influent pH (pH > 7) allowed some Mn(II) oxidation before filtration, resulting in significant manganese removal by MnO_x(s) particle filtration. 2. Although the intent of MnO_x(s)-coating on the filter media was to remove influent Mn(II) from filter-applied water, MnO_x(s) that was removed by particle filtration also provided MnO_x(s) surface area within the filter and, thus, additional sorption sites for Mn(II) removal. 3. Increases in fluid backwashing rate tended to produce greater amounts of MnO_x(s) release from filter media for the duration of these backwash operations. However, backwashing did not result in complete MnO_x(s) release from the media surface; rather, there was always sufficient Mn0O_x(s) retained to permit efficient soluble Mn(II) removal after the filtration operations were restarted. Removal of soluble Mn(II) by sorption and oxidation proved to be a dependable, low-maintenance Mn(II) removal technique that worked well within a wide range of raw water influent conditions. Because the process is cost-effective and easily integrated into new or existing water treatment facilities, it is an economical and competitive alternative for removal of soluble Mn(II)."
Characterization and modeling of soluble manganese removal from drinking water by oxide-coated filter media
Merkle, Peter B. (Virginia Tech, 1995)
Where Mn²⁺ _(aq) is found in water supplies, filter media may naturally develop surface coatings bearing MnO_x(s). These may absorb Mn²⁺ _(aq), and in the presence of oxidant, sorbed Mn²⁺* is oxidized to MnO_x(s), regenerating sorption capacity. The filter accomplishes Mn²⁺ _(aq) removal, a process called the "natural greensand effect". Characterization of naturally coated media showed variation in coating composition and structure. With thicknesses from 1 - 125 μm, primary coating constituents were Al and Mn, with incorporation of minor amounts of Fe, Cu, and Si and trace elements. "Growth ring" features in coating cross-section corresponding to compositional variation were characterized by SEM, electron microprobe, and energy-dispersive x-ray analysis (EDS). Media surface areas of 2 - 135 m² g⁻¹ land microporosity of 15 - 533 cm³ kg⁻¹ were linearly related to extractable Mn content. Diatom remains found in coatings suggest a key role for coating deposition in filtration phenomena. Atomic force microscopy found surface self-similarity over 10 nm - 10 μm. X-ray photoelectron spectroscopy (XPS) confirmed heterogeneous surface composition including C, Al, Si, and Fe. A method to rapidly deposit up to 4 mg g⁻¹ Mn on media was developed, employing sequential batch and recycle reactors. Mn(IV) was the surface species found by XPS analysis. The Freundlich isotherm described Mn²⁺ sorption on this and the naturally coated media; sorption capacity increased between pH 6.0 and 7.5, and was reduced by [Ca²⁺] = 60 mg L⁻¹. The global Mn²⁺ oxidation rates for all coated media at pH 7.5 were 0.008 - 0.11 mg Mn²⁺ g⁻¹ hr⁻¹: rates increased with flow and decreased with pH. A numerical process model for sorption and oxidation of Mn²⁺ _(aq) was calibrated with short bed absorber and differential reactor columns. The Freundlich isotherm, film transport, internal diffusion, and hydrodynamic dispersion were included, with sorption capacity apportioned into kinetically available and unavailable sites. The model performed well in calibration, predicting dynamic system response across a range of flow, pH, [Ca²⁺], and reactant levels. Model performance in validation was less satisfactory, probably due to experimental difficulties and the sensitivity of process performance on recent coating history and media regeneration status.
Characterization of Metallic Flavor in Drinking Water: An Interdisciplinary Exploration through Sensory Science, Medicine, Health, and the Environment
Mirlohi, Susan (Virginia Tech, 2012-02-22)
Scientific explorations can lead to life changing discoveries or light the path for new discoveries as scientists continue to carry or pass on the torch of knowledge to current and future generations. This torch of knowledge radiates in many directions, as the path of discovery often demands a multidimensional perspective. This research explored the many aspects of metallic flavor in drinking water through applications of sensory science, medicine, health, and the environment. Humans interact with their environment through the five senses and are often exposed to contaminants through multiple routes; oral intake of trace metal contaminants through drinking water is a likely source. The biochemical mechanism by which humans are able to detect the flavor of strongly metallic agents such as iron has been previously elucidated, but little is known about population variability in the ability to sense metallic flavors. This research evaluated sensory thresholds and biochemical indicators of metallic flavor perception in healthy adults for ferrous iron in drinking water; 61 subjects aged 19 – 84 years, participated. The findings demonstrated an age-dependent sensitivity to iron indicating as people age they are less sensitive to metallic perception; impairment of olfactory functions is a contributing factor. Unlike in healthy adults, where human senses are often protective of overexposure to contaminants, and supportive of sensations of everyday life's pleasures, cancer patients often suffer from chemosensory dysfunctions. Metallic phantom taste is a commonly experienced sensation, yet very little studied aspect of this debilitating disorder. Impact of cancer therapy on chemosensory functions of patients with malignant brain tumors undergoing combined modality treatment (CMT) was explored. The results indicated that chemosensory dysfunctions of the patients can range from minimal to moderate impairment with maximum impairment developing during the 6-week CMT. Study of salivary constituents may provide clues on to the causes of chemosensory dysfunctions. On health aspects, implication of individual sensitivity to metallic flavor on beverage choices and overall water consumption was assessed in 33 healthy adults through self-reported beverage questionnaire. The results indicated that among the elderly reduced intake of drinking water coincided with reduced sensitivity to metallic flavor. The findings have important health implications in terms of hydration status and beverage choices. Finally, with environmental exposure relevance, preliminary findings on sensory properties of zerovalent iron nanoparticles (nZVI) indicated that oral exposure to nZVI may induce sensory properties different from that of ferrous iron, likely predictive of a diminished detection of metallic flavor by humans. Further research is warranted in this area.
Characterizing Waterborne Lead in Private Water Systems
Pieper, Kelsey J. (Virginia Tech, 2015-07-21)
Lead is a common additive in plumbing components despite its known adverse health effects. Recent research has attributed cases of elevated blood lead levels in children and even fetal death with the consumption of drinking water containing high levels of lead. Although the federal Environmental Protection Agency (USEPA) strives to minimize lead exposure from water utilities through the Lead and Copper Rule (LCR), an estimated 47 million U.S. residents reliant on private unregulated water systems (generally individual and rural) are not protected. Detection, evaluation, and mitigation of lead in private systems is challenging due to lack of monitoring data, appropriate sampling protocols, and entities to fund research. Through a statewide sampling survey, over 2,000 homeowners submitted water samples for analysis. This survey documented that 19% of households had lead concentrations in the first draw sample (i.e., 250 mL sample collected after 6+ hours of stagnation) above the EPA action level of 15, with concentrations as high as 24,740. Due to the high incidence observed, this research focused on identifying system and household characteristics that increased a homeowner's susceptibility of lead in water. However, 1% of households had elevated lead concentrations after flushing for five minutes, which highlighted potential sources of lead release beyond the faucet. Therefore, a follow-up study was conducted to investigate sources and locations of lead release throughout the entire plumbing network. Using profiling techniques (i.e., sequential and time series sampling), three patterns of waterborne lead release were identified: no elevated lead or lead elevated in the first draw of water only (Type I), erratic spikes of particulate lead mobilized from plumbing during periods of water use (Type II), and sustained detectable lead concentrations (>1 ) even with extensive flushing (Type III). Lastly, emphasis was given to understand potential lead leaching from NSF Standard 61 Section 9 certified lead-free plumbing components as the synthetic test water is not representative of water quality observed in private water systems. Overall, this dissertation research provides insight into a population that is outside the jurisdiction of many federal agencies.
Chemical Contaminants in Drinking Water: An Integrated Exposure Analysis
Khanal, Rajesh (Virginia Tech, 1999-05-10)
The objective of this research is to develop an integrated exposure model, which performs uncertainty analysis of exposure to the entire range of chemical contaminants in drinking water via inhalation, ingestion and dermal sorption. The study is focused on a residential environment. The various water devices considered are shower, bath, bathroom, kitchen faucet, washing machine and the dishwasher. All devices impact inhalation exposure, while showering, bathing and washing hands are considered in the analysis of dermal exposure. A set of transient mass balance equations are solved numerically to predict the concentration profiles of a chemical contaminant for three different compartments in a house (shower, bathroom and main house). Inhalation exposure is computed by combining this concentration profile with the occupancy and activity patterns of a specific individual. Mathematical models of dermal penetration, which account for steady and non-steady state analysis, are used to estimate exposure via dermal absorption. Mass transfer coefficients are used to compute the fraction of contaminant remaining in water at the time of ingestion before estimating ingestion exposure. Three chemical contaminant in water: chloroform, chromium and methyl parathion are considered for detailed analysis. These contaminants cover a wide range in chemical properties. The magnitude of overall exposure and comparison of the relative contribution of individual exposure pathways for each contaminant is evaluated. The major pathway of exposure for chloroform is inhalation, which accounts for 2/3rd of the total exposure. Dermal absorption and ingestion exposures contribute almost equally to the remaining 1/3rd of total exposure for chloroform. Ingestion accounts for about 60% of total exposure for methyl parathion and the remaining 40% of exposure is via dermal sorption. Nearly all of the total exposure (98%) for chromium is via the ingestion pathway.
Chemical Identification and Organoleptic Evaluation of Iodine and Iodinated Disinfection By-Products Associated with Treated Spacecraft Drinking Water
Dodd, Jennifer Peters (Virginia Tech, 1997-02-11)
Aboard the International Space Station, potable water will likely be produced from recycled wastewater. The National Aeronautic and Space Administration (NASA) plans to use iodine as a disinfectant, and, consequently, the formation of iodinated disinfection by-products (IDBPs) requires investigation. Objectives of this research were to determine possible precursors of IDBPs, identify IDBPs formed, and apply flavor profile analysis (FPA) as a tool to evaluate water qaulity. Experiments were performed by separately reacting iodine with each of the following organic compounds: methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, acetone, and formaldehyde. NASA previously identified all of these compounds in wastewater sources under consideration for recycling into potable water. Experiments were performed at pH 5.5 and 8, iodine concentrations of 10 and 50 mg/L, and organic concentrations of 5 and 50 mg/L. Gas chromatography/mass spectrometry was used to identify and monitor the concentrations of organic species. Spectrophotometry was used to monitor the iodine concentration. Acetone was the only compound identified as an IDBP precursor and it reacted to produce iodoacetone and iodoform. Concentrations of iodoform from 0.34 mg/L to 8.637 mg/L were produced at conditions that included each pH level, iodine concentration, and acetone concentration. The greatest iodoform concentration was produced at pH 8 from 50 mg/L of iodine and acetone. FPA indicated that the odor threshold concentration (OTC) of iodoform was 1.5 ug/L, and the OTC of iodine was 500 ug/L. Both iodine and iodoform have medicinal odors, making it difficult to distinguish each compound when present in a mixture.
Chlorine dioxide and by-products in water distribution systems
Ferreira, Francisco Cardoso (Virginia Tech, 1991-12-04)
Chlorine dioxide is used as both a pre-oxidant and/or a post-disinfectant in several water treatment plants in the United States. Chlorine dioxide is associated with its byproducts chlorite and chlorate. Chlorine dioxide, chlorine, chlorite and chlorate were sampled in four distribution systems where chlorine dioxide is used for disinfection purposes: Charleston, WV, Columbus, GA, New Castle, PA, and Skagit, WA. The fate of chlorine dioxide and its by-products in distribution systems is discussed. A constituent transport model (TRAK) was applied to New Castle, PA distribution systems to assess times of travel. No relationship was found between the concentrations of chlorine, chlorine dioxide, chlorite and chlorate and the computed travel times. Water treatment plant and distribution system data received from Galveston, TX where the use chlorine dioxide has being tested is analyzed and discussed. Median chlorine dioxide concentrations are relatively constant in distribution systems with a value of approximately 0.2 mg/L; however, chlorine dioxide dosages applied at the treatment plant can induce different concentrations in the distribution system. Median chlorite concentrations in distribution systems range from 0.5 to 0.8 mg/L while median chlorate concentrations are generally lower in a range between 0.1 to 0.3 mg/L. The effects of distribution systems skeletonization in constituent transport modeling are also presented. Skeletonization does not affect significantly computed times of travel when the median percentage of constituent has to be detected. However, depending on the layout of each distribution system, small variations can be observed.
Chlorine dioxide by-products in drinking water and their control by powdered activated carbon
Grabeel, Margaret N. (Virginia Tech, 1992-05-05)
The concentrations of chlorine dioxide (CI02), chlorine, chlorite (CIO2), and chlorate (CI03) were evaluated following pretreatment of raw water by CI02 at water treatment plants in New Castle, Pennsylvania; Charleston, West Virginia; Skagit, Washington; and Columbus, Georgia. Chlorite and chlorate concentrations were unaffected by any of the water treatment processes and did not vary as a function of time of travel in the distribution system. Chlorine dioxide, which was analyzed on-site at two water treatment plants, reformed in the clear well and in the distribution system following post chlorination. The chlorite-removal capability of powdered activated carbon (PAC) was evaluated in both laboratory- and pilot-scale studies. Chlorite removal by PAC in laboratory studies decreased with increasing pH over a range from pH 5.5 to 7.5 and varied with the type of PAC. Chlorite was reduced to chloride at pHs ranging from 5.5 to 7.5, but CI03- formed at the pH 5.5 through 6.0. The pilot plant study; which was conducted at Newport News, Virginia; evaluated CI02 removal by PAC enmeshed in a floc blanket in a pulsed-bed, solids-contact clarifier. An average of 27 percent of the CI02 was removed when the PAC dose was 10 mg/L PAC and 57 percent when it was 20 mg/L PAC. Chlorate was not removed by PAC, but the concentrations could be reduced if the CIOz generator was properly operated.
Comparing Two Methods for Developing Local Sediment TMDLs to Address Benthic Impairments
Wallace, Carlington W. (Virginia Tech, 2012-04-23)
Excessive sedimentation is a leading cause of aquatic life use impairments in Virginia. As required by the Clean Water Act, a total maximum daily load (TMDL) must be developed for impaired waters. When developing a TMDL for aquatic life use impairment where sediment has been identified as the primary pollutant, the target sediment load is often determined using a non-impaired reference watershed, i.e., the reference watershed approach (RWA). The RWA has historically been used in Virginia to establish TMDL target sediment loads because there is no numeric ambient water quality criterion for sediment. The difference between the sediment load generated by the reference watershed and the load generated by the impaired watershed is used to determine the sediment load reduction required to meet the TMDL target load in the impaired watershed. Recent quantification of the Chesapeake Bay TMDL based on Phase 5.3 of the Chesapeake Bay Watershed Model (CBWM) offers a simpler and potentially more consistent method of calculating target sediment loads for impaired watersheds within the Chesapeake Bay watershed. Researchers in the Biological Systems Engineering department at Virginia Tech have developed the "disaggregate method" (DM) which uses landuse inputs to, and pollutant load outputs from, the CBWM to determine pollutant load reductions needed in watersheds whose areas are smaller than the smallest modeling segments generally used in the CBWM. The DM uses landuse-specific unit area loads from two CBWM model runs (an existing condition run and TMDL target load run) and a finer-scale, locally assessed landuse inventory to determine sediment loads. The DM is simpler and potential more consistent than the reference watershed approach. This study compared the reference watershed approach and the disaggregate method in terms of required sediment load reduction. Three sediment-impaired watersheds (Long Meadow Run, Taylor Creek and Turley Creek) within the Chesapeake Bay watershed were used for the study. Study results showed that the TMDL development method used to determine sediment loads would have noticeable effects on resulting sediment-load reduction requirements. For Taylor Creek, the RWA required 20.4 times greater reductions in sediment load (tons/yr) when compared to the DM. The RWA also required 9.2 and 10.4 times greater reductions for Turley Creek and Long Meadow Run watersheds, respectively. On a percentage basis, the RWA for reduction Taylor Creek was 7.3 times greater than that called for by the DM. The RWA called for 4.4 and 4.6 times greater percent reductions for Turley Creek and Long Meadow Run watersheds, respectively. An ancillary objective of this research was to compare the sediment load reductions required for the impaired and their respective RWA-reference watersheds, using the DM. This comparison revealed that, both Taylor Creek and Turley Creek watersheds required less sediment load reduction than their respective reference watersheds, while the load reductions required for Long Meadow Run were slightly greater than its reference watershed. There are several issues associated with either the RWA or the DM for developing sediment TMDLs. Those issues are discussed in detail. Recommendations the need for further studies, based in questions raised by the research presented here are also discussed.
Comparison and Simulation of a Water Distribution Network in EPANET and a New Generic Graph Trace Analysis Based Model
Newbold, James Richard (Virginia Tech, 2009-01-27)
The main purpose of this study was to compare the Distributed Engineering Workstation (DEW) and EPANET models. These two models are fundamentally different in the approaches taken to simulate hydraulic systems. To better understand the calculations behind each models' hydraulic simulation, three solution methods were evaluated and compared. The three solution approaches were the Todini, Hardy-Cross, and DEW bisection methods. The Todini method was included in the study because of its similarities to EPANET's hydraulic solution method and the Hardy-Cross solution was included due to its similarities with the DEW approach. Each solution method was used to solve a simple looped network, and the hydraulic solutions were compared. It was determined that all three solution methods predicted flow values that were very similar. A different, more complex looped network from the solution method comparison was simulated using both EPANET and DEW. Since EPANET is a well established water distribution system model, it was considered the standard for the comparison with DEW. The predicted values from the simulation in EPANET and DEW were compared. This comparison offered insight into the functionality of DEW's hydraulic simulation component. The comparison determined that the DEW model is sensitive to the tolerance value chosen for a simulation. The flow predictions between the DEW and EPANET models became much closer when the tolerance value in DEW was decreased.
Comparison of 1-D and 2-D modeling approaches for simulating runoff and sediment transport in overload areas
Hong, Seonggu (Virginia Tech, 1995-10-26)
One-dimensional and two-dimensional modeling approaches were compared for their abilities in predicting overland runoff and sediment transport. Both the I-D and 2-D models were developed to test the hypothesis that the 2-0 modeling approach could improve the model predictions over the 1-0 approach, based on the same mathematical representations of physical processes for runoff and sediment transport. Runoff processes were described based on the St. Venant equations and the sediment transport was based on the continuity relationship. The finite element method was employed to solve the governing equations. The nonlinear, time-dependent system of equations obtained by the finite element formulation was solved by the substitution method and the implicit method. The models were verified by comparing the analytical solutions presented by Singh and Regl (1983) and the solution by the Izzard method (Chow, 1959). The comparison showed that both the 1-0 and 2-D models provided reasonable estimations of runoff and sediment loadings. Evaluation of the models was based on four different hypothetical case studies and two experimental studies. The hypothetical case studies investigated the effects of the discretization level, cross slopes, and the size of the field area on the model predictions. The two experimental studies provided a comparison of model predictions with observed data. The results of the hypothetical case studies indicated that the maximum differences in the model predictions at the outlet were about 30% between the two modeling approaches. When the discretization level was sufficient to reasonably describe the shape of the surface, the 1-0 model prediction were almost the same as the 2-D model predictions. Even though cross slopes existed in the field, the differences in the model predictions at the outlet were not significant between the 1-0 and 2-0 models. The differences in the model predictions of runoff and sediment loading were not affected by the changes in the size of the field. Since the 2-D model resulted in 10 to 20% differences in model predictions when different boundary conditions were used and the 1-D model predictions were also affected by the choice of element length, the differences in model predictions at the outlet, shown in model application results, which were less than 30% in most cases, could not be considered significant. The model applications to the experimental studies also showed that no substantial differences existed in the model predictions between the I-D and 2-D models. Even though the spatial distributions of the flow depth and sediment concentration were significantly different, runoff volumes and sediment yields at the outlet showed less than 10% differences. Compared with the I-D model, the 2-D model required much more computational time and effort to simulate the same problems. In addition, convergence problems due to negative flow depths limited the 2-D model applications. The 2-D simulations required more than twice the computational time needed for the I-D simulations. As long as the model predictions at the outlet are concerned, the much greater computational costs and efforts could not justify the use of the 2-D approach. Based on the simulation results from the selected hypothetical case and experimental studies, the 2-D model provided better representations of spatial distribution of flow depths and sediment concentrations than the I-D model. However, no substantial differences in predictions of total runoff volume and sediment yield at the outlet area were found between the I-D and 2-D models.

Browsing by Author "Gallagher, Daniel L."

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