VTechWorks Repository :: Browsing by Author "Edwards, Marc A."

Browsing by Author "Edwards, Marc A."

Now showing 1 - 20 of 162

Addressing and Assessing Lead Threats in Drinking Water: Non-Leaded Brass, Product Testing, Particulate Lead Occurrence and Effects of the Chloride to Sulfate Mass Ratio on Corrosion
Triantafyllidou, Simoni (Virginia Tech, 2006-09-11)
Growing concern over adverse health effects from low level lead exposure motivated reassessment of lead occurrence in drinking water, from the perspective of 1) possibly eliminating lead from new brass materials, and 2) performance testing of existing products. During the course of this thesis work, it was discovered that several cases of childhood lead poisoning in North Carolina, South Carolina and Washington D.C. occurred from contaminated potable water. That disconcerting finding prompted additional work into 3) deficiencies in existing lead testing of drinking water samples, and 4) impacts of water treatment steps on lead leaching. Meters, components, and fittings manufactured from non-leaded brass (< 0.25 percent lead content) are increasingly specified for use in water distribution systems and premise plumbing, in response to California's Proposition 65 and the proposed Lead Free Drinking Water Act. An in-depth review of the available literature revealed that non-leaded brass releases minimal amounts of lead and other contaminants of concern to drinking water. There is legitimate concern about the corrosion resistance and longevity of these non-leaded alloys in the range of waters that will be encountered in practice. Nonetheless, when the potential impacts to manufacturers, utilities and consumers are considered, non-leaded brasses appear to be attractive albeit at slightly higher cost. For existing leaded brass products, concerns have been raised over potential limitations of performance standards used to certify the products as "safe" in the marketplace. The ANSI/NSF 61 Section 9 test is the industry standard, and its protocol is critically evaluated from the perspective of the leaching solution chemistry. Testing indicated that the protocol water is reasonably representative of a typical water supply. However, some lower pH and lower alkalinity waters can be much more aggressive than the existing section 9 water, and for potable water with these characteristics, problems with higher than desired lead leaching may occur. It may be desirable to tighten the standard's pass/fail lead criterion in order to account for this problem in practice. Several cases of childhood lead poisoning from water have been recently encountered, which prompted environmental assessments. It was visually obvious that some of the lead particles ingested by these children, present in water from the tap, were not completely dissolving in the standard method with weak acid recommended by the US EPA. A laboratory investigation proved that up to 80% particulate lead in water samples could be "missed" by the standard protocol. Unfortunately, tests with simulated gastric fluid revealed that much of this particulate lead would be bioavailable in the presence of chloride, warmer temperatures and lower pH inside the human stomach. It is recommended that water utilities be alert to this possible problem and that environmental assessments of lead poisoned children use stronger digestions to detect lead in water. Several of the lead poisoning instances occurred after the utility changed both disinfectant chemicals (from chlorine to chloramine) and coagulant types. Although authorities initially thought chloramine was the cause based on experiences in Washington D.C., bench scale studies in this work proved that a change in coagulant from aluminum sulfate to either ferric chloride or polyaluminum chloride was in fact the main reason of the lead spikes. The reduction in sulfate and increase in chloride increased the chloride to sulfate mass ratio of the water supply. A higher chloride to sulfate mass ratio triggered much higher (2.3-40 times more) lead leaching from solder connected to copper pipe. The adverse effects of the increase in the ratio could not be eliminated by adding a corrosion inhibitor.
Addressing gaps in the US EPA Lead and Copper Rule: Developing guidance and improving citizen science tools to mitigate corrosion in public water systems and premise plumbing
Kriss, Rebecca Boyce (Virginia Tech, 2023-06-21)
Lead and copper in drinking water are known to pose aesthetic and health concerns for humans and pets. The United States Environmental Protection Agency (US EPA) Lead and Copper Rule (LCR) set 90th percentile action levels for lead (15 ppb) and copper (1.3 mg/L), above which utilities must implement systemwide corrosion control. However, gaps in the US EPA LCR leave at least 10% of residents using municipal water and all private well users vulnerable to elevated lead and copper in their drinking water. To help address these gaps in the LCR, this dissertation 1) Evaluates accuracy of at-home lead in water test kits to help residents identify lead problems, 2) Refines orthophosphate corrosion control guidance to help reduce cuprosolvency, 3) Identifies challenges to mitigating cuprosolvency by raising pH, and 4) Develops guidance that can help residents assess and address cuprosolvency problems. Lead in drinking water can pose a variety of health concerns, particularly for young children. The revised LCR will still leave many residents unprotected from elevated lead in their drinking water and potentially wondering what to do about it. Many consumers concerned about lead may choose to purchase at-home lead in water test kits, but there is no certification authority to ensure their accuracy. Most off-the-shelf tests purchased in this work (12 of 16) were not able to detect dissolved or particulate lead at levels of concern in drinking water (i.e. near the lead action level of 15 ppb) due to high detection limits (5,000-20,000 ppb). Binary type tests, which indicate the presence or absence of lead based on a trigger threshold of 15 ppb, were often effective at detecting dissolved lead, but they failed to detect the presence of leaded particles that often cause high lead exposures in drinking water problems. Some of these problems detecting particles could be reduced using simple at-home acid dissolution with weak household acids such a vinegar or lemon juice. Our analysis points out the strengths and weaknesses of various types of at-home lead in water tests, which could be particularly important considering potential distrust in official results in the aftermath of the Flint Water Crisis. Elevated cuprosolvency, or copper release into drinking water, can be an aesthetic concern due to fixture staining, blue water, and green hair and can pose health concerns for residents and pets. In addition to the general gaps in the LCR described above, compliance sampling in the LCR focuses on older homes at highest risk of elevated lead, rather than the newer homes at highest risk of elevated copper. Problems with elevated copper can sometimes go undetected as a result. Guidance was developed to help proactive utilities address cuprosolvency issues through the addition of orthophosphate corrosion inhibitors or pH adjustment as a function of a water's alkalinity. Linear regressions developed from pipe cuprosolvency tests (R2>0.98) determined a "minimum" orthophosphate dose or a "minimum" pH for a given alkalinity that was expected to almost always reduce copper below the 1.3 mg/L EPA action level in a reasonable length of time. The subjective nature of the terms "almost always" and "reasonable length of time" were quantitatively discussed based on laboratory and field data. Orthophosphate addition was generally very effective at cuprosolvency control. Orthophosphate treatment in copper tube cuprosolvency tests produced cuprosolvency below the action level within the first week of treatment. As expected, orthophosphate treated waters sometimes resulted in higher long-term cuprosolvency than the same waters without orthophosphate corrosion control treatment. This is consistent with the formation of phosphate scales which have an intermediate solubility between the cupric hydroxide in new pipes and the malachite or tenorite scales expected in pipe aging without orthophosphate. A linear regression (R2>0.98) was used to determine the orthophosphate dose needed for a given alkalinity to yield copper below the 1.3 mg/L action level in the pipe segments with the highest, 2nd highest, 3rd highest copper concentrations (100th, 95th, or 90th percentile, n=20 replicates, five each from four manufacturers) after 4 or 22 weeks of pipe aging. This regression was generally in good agreement with a bin approach put forth in the 2015 Consensus Statement from the National Drinking Water Advisory Council, but in some cases the regression predicted that higher orthophosphate doses would be needed. In contrast, due to the greater complexity of the reactions involved, a similar simplistic approach for pH adjustment is not widely applicable. A linear regression predicted that higher "minimum" pH values would be needed to control cuprosolvency compared to those suggested by the 2015 National Drinking Water Advisory Consensus Statement. Results indicate that factors such as the potential for calcite precipitation, pipe age, and significant variability in cuprosolvency from pipes of different manufacturers may warrant further research. Field LCR monitoring data indicated that 90th percentile copper concentrations continued to decline over a period of years or decades when orthophosphate is not used, and our laboratory results demonstrate a few cases where copper levels even increased with time. Consideration of confounding effects from other water quality parameters such as natural organic matter, silica, and sulfate would be necessary before the "minimum" pH criteria could be broadly applied. Guidance was then developed to help address cuprosolvency issues on a single building or single home basis for residents with private wells or those with high copper in municipal systems meeting the LCR. A hierarchy of costs and considerations for various interventions are discussed including replumbing with alternative materials, using bottled water or point use pitcher, tap, or reverse osmosis filters to reduce copper consumption, and using whole house interventions like more conventional orthophosphate addition and pH adjustment, or unproven strategies like granular activated carbon filtration, reverse osmosis treatment, and ion exchange treatment. Laboratory and citizen science testing demonstrated that some inexpensive at-home tests for pH and copper, were accurate enough to serve as inputs for this guidance and could empower consumers to diagnose their problems and consider possible solutions. Citizen science field testing and companion laboratory studies of potential interventions indicate that short-term (<36 weeks) use of pH adjustment, granular activated carbon, anion exchange and reverse osmosis treated water were not effective at forming a protective scale for the resident's water tested. In this case-study, cuprosolvency problems were ultimately related to water chemistry and linked to variability in influent water pH. Overall, this work highlighted weaknesses in the current US EPA Lead and Copper Rule. It attempted to close some of these gaps by assessing the accuracy of at-home citizen science tests for lead and copper detection and developing guidance to support voluntary interventions by utilities or consumers. Ideally, local authorities (utilities, health departments, cooperative extension programs) could adapt this guidance to account for local water quality considerations and support consumers in resolving cuprosolvency issues. This guidance may also serve as a citizen science approach that some consumers could use to make decisions on their own. Future work could extend and improve on these initial efforts.
Addressing the Contribution of Indirect Potable Reuse to Inland Freshwater Salinization
Bhide, Shantanu V.; Grant, Stanley B.; Parker, Emily A.; Rippy, Megan A.; Godrej, Adil N.; Kaushal, Sujay S.; Prelewicz, Gregory; Saji, Niffy; Curtis, Shannon; Vikesland, Peter J.; Maile-Moskowitz, Ayella; Edwards, Marc A.; Lopez, Kathryn; Birkland, Thomas A.; Schenk, Todd (2021-02-02)
Inland freshwater salinity is rising worldwide, a phenomenon called the freshwater salinization syndrome (FSS). We investigate a potential conflict between managing the FSS and indirect potable reuse, the practice of augmenting water supplies through the addition of reclaimed wastewater to surface waters and groundwaters. From time-series data collected over 25 years, we quantify the contributions of three salinity sources—a wastewater reclamation facility and two rapidly urbanizing watersheds—to the rising concentration of sodium (a major ion associated with the FSS) in a regionally important drinking water reservoir in the Mid-Atlantic United States. Sodium mass loading to the reservoir is primarily from watershed runoff during wet weather and reclaimed wastewater during dry weather. Across all timescales evaluated, sodium concentration in the reclaimed wastewater is higher than in outflow from the two watersheds. Sodium in reclaimed wastewater originates from chemicals added during wastewater treatment, industrial and commercial discharges, human excretion, and down-drain disposal of drinking water and sodium-rich household products. Thus, numerous opportunities exist to reduce the contribution of indirect potable reuse to sodium pollution at this site, and the FSS more generally. These efforts will require deliberative engagement with a diverse community of watershed stakeholders and careful consideration of the local political, social, and environmental context.
Advancing Fundamental Understanding of Lead-Tin Solder Corrosion in Drinking Water: Nitrate Spallation Mechanism, Inhibition by Zinc Orthophosphate and Free Chlorine, and Implications for Canned Foods
Lopez, Kathryn G. (Virginia Tech, 2023-10-25)
Given rising concern over elevated lead in drinking water in the aftermath of the Flint Water Crisis, forthcoming revisions to the U.S. EPA Lead and Copper Rule (LCR), and federal funding designated for replacing lead service lines, lead-tin solder corrosion control will become increasingly important. Lead-tin solder is often a dominant source of lead in drinking water for homes built before 1986 and has been the source of several recent high-profile water lead contamination events. This dissertation advances fundamental understanding of lead-tin solder corrosion by demonstrating that 1) elevated nitrate in water can trigger severe solder corrosion associated with very high LCR action level exceedances, 2) spallation of metallic solder to water is a source of lead contamination, 3) zinc orthophosphate offers superior corrosion control to mitigate nitrate attack, and 4) free chlorine can inhibit solder corrosion by electrochemical reversal. These principles were also applied to an exemplary related problem of lead contamination of food stored in tin cans. The conventional understanding is that lead-tin solder corrosion is worsened by low pH, low alkalinity, and elevated chloride relative to sulfate, but a utility that recently switched to a source water previously classified as non-corrosive suffered severe contamination from lead solder. The incident was characterized by the detachment of large chunks of metallic, lead-bearing solder particles from copper pipe joints that sometimes clogged aerators of consumers' faucets. It also caused a 90th percentile lead level of 131 ppb, which was much higher than reported for the 2001-2004 Washington D.C. lead crisis (79 ppb) or the 2014- 2016 Flint, MI water lead crisis (29 ppb). An exhaustive investigation of possible causes eventually revealed a strong correlation (r2=0.79) between seasonal fluctuations in surface water nitrate levels and the 90th percentile lead. The association of high lead with nitrate was unambiguously proven in bench-scale experiments using both copper coupons with new 50:50 lead-tin solder and harvested pipes with aged solder (extracted from a home with ongoing lead release issues) that replicated the characteristic spallation of solder particles (up to 7-mm in length) to water. Lead levels were occasionally >1,000 ppb in homes and >100,000 ppb in the bench experiments with harvested pipe after exposure to high nitrate above 8 mg/L. This finding is especially concerning given that nitrate is not currently identified as a factor affecting solder corrosion in EPA corrosion control guidance and source water contamination by nitrate is increasingly problematic. It was critically important to identify the mechanism by which nitrate caused solder spallation. Analysis of lead-tin solder surfaces in the bench-scale tests and harvested pipes indicated that nitrate preferentially attacked tin in the solder alloy. Nitrate severely detinned solder alloys > 40% tin by weight, causing cracking and detachment of metallic chunks of lead-tin solder from copper surfaces in a matter of weeks. Pure lead and alloys with less than 30% tin corroded more uniformly in the presence of nitrate and were not subject to spallation. Nitrate is reduced to a combination of ammonia and other nitrogenous compounds via reduction reactions that drove lead-tin solder corrosion at the anode. Nitrate also caused 1.3 times more metal weight loss by corrosion than could be explained by Faraday's law even in short-term 32-hour experiments, consistent with a previously identified "chunk effect" and anomalously high tin anode weight loss in nitrate solutions. This severe solder spallation mechanism has never been reported previously in drinking water environments and seems to be unique to nitrate for high tin-content alloys. This discovery also raises concerns about the possibility of pipe joint failures using lead-free tin-based solders that became more commonplace after the federal ban on lead solder in 1986. Common corrosion control strategies, including the use of phosphate corrosion inhibitors, failed to adequately reduce 90th percentile lead levels at the utility affected by runoff water with high nitrate after 6 months of application. Studies using new lead-tin solder and harvested pipes with aged solder demonstrated that zinc orthophosphate outperformed orthophosphate in controlling corrosion in high nitrate water and reduced lead release by 82-90% compared to phosphate alone or no inhibitor. The benefits of zinc orthophosphate improved with time and the dose of zinc delivered to the pipes. When zinc orthophosphate was applied at the water treatment plant, the 90th percentile lead levels in the affected community fell below the action level within 6 months. Analysis of the pipe scale demonstrated that zinc orthophosphate works by coating the interface usually subject to intense galvanic corrosion between copper and solder. Disinfectants may also play a role in controlling lead contamination from solder. Two water utilities in the Pacific Northwest experienced lead action level exceedances for decades due to solder corrosion while using the same source water with chloramine disinfectant. After one utility switched to a similar water source using free chlorine disinfectant, lead release dropped to low levels within months. This was consistent with laboratory experiments conducted at the second utility more than three decades ago that indicated much lower lead release using free chlorine versus chloramine using the water utility's source water. There was previously no explanation for the benefits from free chlorine, but it was recently demonstrated that chlorine can cause electrochemical reversal of a copper-lead pipe galvanic cell, which dramatically reduced lead release to water. It was hypothesized that a similar reaction could occur for lead-tin solder as well. This was confirmed when lead-tin solder and copper connections exposed to 4 mg/L free chlorine in circulating rigs experienced electrochemical reversal in some waters over a period of weeks. The electrochemical reversal was accompanied by dramatic decreases in lead release, concomitant with the formation of insoluble lead (IV) oxide scale. In some situations where traditional corrosion inhibitors are not effective, it is possible that electrochemical reversal due to free chlorine may control lead solder corrosion, either unintentionally or purposefully. This new understanding of nitrate's ability to exacerbate lead contamination from lead-tin alloys in drinking water was then extended to concerns about lead contamination of food stored in tin-plated cans. Fruits and their juices can contain nitrate, and if lead is present in the tin plating, the resulting corrosion is predicted to cause significant contamination. Twenty-one brands of canned pears from across the U.S. were assessed for lead content, and one brand was found to contain 2-3 times higher lead in the fruit (average=14 ppb, max=38 ppb) and syrup (average=7 ppb, max=15 ppb) than other brands. The brand of cans with higher lead in the fruit also had higher levels of lead in the can materials: surface lead levels in the interior tin-plate was 0.1% by mass on average (max=0.60%) and 7.5% by mass on average (max=29%) in the interior seam, which is up to 146 times the 0.2% value advised in FDA guidelines for lead in food-contact surfaces. Follow-up testing with three brands of canned pears confirmed lead levels in the syrup were also associated with higher levels of ammonia in the juice—ammonia is a reaction product of nitrate corrosion of tin in the can. To confirm that the can material was the source of the lead contamination, the pear cans were emptied and then refilled with a variety of synthetic solutions containing up to 50 mg/L NO3-N. The higher nitrate levels always formed ammonia and were associated with higher lead release in some cases. The use of lead-tin alloys (either lead-bearing tin-plate or solder) in unlined canned goods with solutions known to contain nitrates can create unnecessary lead exposure for consumers. This dissertation provides novel insights into lead-tin solder corrosion with profound implications for water lead contamination, the integrity of potable water infrastructure, and corrosion control strategies in potable water. Rising concerns about nitrate contamination of source waters underscore the importance of understanding these effects on lead and public health. As illustrated by the application of these principles to lead contamination of tin-lined fruit cans, the results may also enhance understanding of corrosion of tin-based materials in electronics, museum artifacts, electrochemical water treatment, and in the automotive and aerospace industries.
Advancing Microbial Desalination Cell towards Practical Applications
Ping, Qingyun (Virginia Tech, 2016-11-03)
Conventional desalination plant, municipal water supply and wastewater treatment system are among the most electricity-intensive facilities. Microbial Desalination Cell (MDC) has emerged as a promising technique to capture the chemical energy stored in wastewater directly for desalination, which has the potential to solve the high energy consumption issue in desalination industry as well as wastewater treatment system. The MDC is composed of two critical components, the electrodes (anode and cathode), and the ion-exchange membranes separating the two electrodes which drive anions migrate towards the anode, and cations migrate towards the cathode. The multiple components allow us to manipulate the configuration to achieve most efficient desalination performance. By coupling with Donnan Dialysis or Microbial Fuel Cell, the device can effectively achieve boron removal which has been a critical issue in desalination plants. The uncertainty of water quality of the final desalinated water caused by contaminant back diffusion from the wastewater side can be theoretically explained by two mechanisms, Donnan exchange and molecule transport which are controlled by bioelectricity and concentration gradient. Scaling and fouling is also a factor needs to be taken into consideration when operating the MDC system in real world. With mathematical modeling, we can provide insight to bridge the gap between lab-scale experiments and industrial applications. This study is expected to provide guidance to enhance the efficiency as well as the reliability and controllability of MDC for desalination.
Advancing Monitoring and Mitigation of Antibiotic Resistance in Wastewater Treatment Plants and Water Reuse Systems
Majeed, Haniyyah JaRae (Virginia Tech, 2020-10-22)
Wastewater treatment plants (WWTPs) receive a confluence of sewage containing antibiotics, antibiotic resistant bacteria, antibiotic resistance genes (ARGs), and pathogens, thus serving as key point of interest for the surveillance of antibiotic resistance (AR) dissemination. This thesis advances knowledge about the fate of AR indicators throughout treatment and reuse. The field study informs approaches for monitoring AR at a WWTP by characterizing the resistome (i.e., full profile of ARGs) and microbiome across eight sampling events via metagenomic sequencing, complemented by antibiotic data. The WWTP significantly reduced the total load of ARGs and antibiotics, although correlations between ARGs and antibiotics were generally weak. Quantitative polymerase chain reaction was applied to validate the quantitative capacity of metagenomics, whereby we found strong correlations. The influent and effluent to the WWTP were remarkably stable with time, providing further insight into the sampling frequency necessary for adequate surveillance. The laboratory study examined the effects of commonly applied disinfection processes (chlorination, chloramination, and ultraviolet irradiation [UV]) on the inactivation of antibiotic resistant pathogens and corresponding susceptible pathogens in recycled and potable water. Further, we evaluated their regrowth following disinfection by simulating distribution. Acinetobacter baumannii, an environmental opportunistic pathogen, regrew especially well following UV disinfection, although not when a disinfectant residual was present. Enterococcus faecium, a fecal pathogen, did not regrow following any disinfection process. There were no significant differences between water types. The findings of this study emphasize a need to move beyond the framework of assessing treatment efficacy based on the attenuation of fecal pathogens.
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.
Advancing the Understanding of Water Distribution System Corrosion: Effects of Chlorine and Aluminum on Copper Pitting, Temperature Gradients on Copper Corrosion, and Silica on Iron Release
Rushing, Jason Clark (Virginia Tech, 2002-07-24)
When severe copper pitting problems impacted customers at a large utility, studies were begun to attempt to diagnose the problem and identify potential solutions. A series of tests were conducted to characterize the nature of pitting. Desktop comparisons of pinhole leak frequency and treatment practices at nearly utilities were also documented to identify treatment factors that might be influencing the initiation and propagation of leaks. Factors identified included the presence of relatively high levels of free chlorine and aluminum in the distribution system. Experiments were conducted to examine the effect of these constituents on copper pitting under stagnant and flow conditions. That led to discovery of a synergistic redox reaction between chlorine, aluminum solids, and copper metal as evidenced by increased chlorine decay rates, non-uniform corrosion, and rising corrosion potentials. Temperature changes had been suspected to increase copper pitting frequency and copper release to drinking water. Experiments examined the effect of temperature gradients on copper pipe corrosion during stagnant conditions. The pipe orientation in relation to the temperature gradient determined whether convective mixing would occur, which influenced temperature gradients within the pipe. This work is the first to demonstrate that temperature gradients lead to thermogalvanic currents, influences copper leaching and scale type. Iron release from corroding water mains is another concern of many water utilities, but little is known about chemistry factors that influence the problem. In laboratory experiments, higher levels of silica caused more iron release to the water and decreased the size of suspended iron particles. Silica levels also changed during the experiment: it decreased through incorporation into a dense scale, and increased by release from cast iron during corrosion. Silica slightly decreased iron corrosion rates near the end of this 6-month test.
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.
Aqueous Silica in the Environment: Effects on Iron Hydroxide Surface Chemistry and Implications for Natural and Engineered Systems
Davis, Christina Clarkson (Virginia Tech, 2000-05-09)
Aqueous silica is present in all natural waters and exhibits a high affinity for the surfaces of iron oxides. Therefore, it is expected to play an important role in environmental systems. Experiments were conducted to investigate the fundamentals of silica sorption onto pre-formed ferric hydroxide at pH 5.0-9.5 and silica concentrations of 0-200 mg/L as SiO₂. Over the entire pH range studied, sorption densities exceeding monolayer sorption were observed at silica levels typical of natural waters. Under some circumstances, sorption exceeded a monolayer while the particle zeta potential remained positive, a phenomenon which is inconsistent with available models. To address this deficiency, an extended surface complexation model was formulated in which soluble dimeric silica sorbs directly to iron surface sites. This model fits sorption density data up to 0.40 mol SiO₂/mol Fe, and it accurately predicts trends in zeta potential and the observed H⁺ release during silica sorption to ferric hydroxide at pH 5.0 and 6.0. A second phase of research was aimed at identifying the practical implications of silica sorption to iron hydroxide in natural and engineered systems. Two types of surfaces were prepared by exposing pre-formed Fe(OH)₃ to aqueous silica (0-200 mg/L as SiO₂) for periods of 1.5 hours or 50 days. The concentration of pre-formed iron passing through a 0.45 micron pore size filter at pH 6.0-9.5 increased as the solids aged in the presence of silica. Consistent with formation of small, stable colloids, "soluble" iron concentrations exceeded 0.2 mg/L only at zeta potentials < -15 mV. When arsenate was added to iron hydroxide particles equilibrated with silica for 1.5 hours, percentage arsenate removals were high. In contrast, arsenate removals decreased markedly as pH and silica concentrations increased if silica was pre-equilibrated with the iron for 50 days. Trends in percentage removal of humic substances were similar. Competition for sorption sites was the main cause of hindered anionic contaminant removal. However, interference with hydrolysis and precipitation are expected to be important under some circumstances, particularly during water treatment.
Assessing Vulnerabilities to the Spread of Pathogens and Antibiotic Resistance in Agricultural and Water Systems Using Culture-, Molecular-, and Metagenomic-based Techniques
Keenum, Ishi M. (Virginia Tech, 2021-09-09)
As climate change exacerbates water scarcity and alters available water and fertilizer resources, it is vital that take appropriate measures to ensure sustainable treatment of water, wastewater, and other waste streams that are protective of public health and support recovery and reuse of water and nutrients. The overarching theme of this dissertation is the advancement of next-generation DNA sequencing (NGS) and computational tools for achieving these goals. A suite of relevant fecal and environmental opportunistic pathogens are examined using both culture-based and NGS-based methods. Of particular concern to this research was not only the attenuation and inactivation of pathogens, but also ensuring that optimal treatment approaches reduce antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Key systems that were the focus of this effort included nutrient reuse (wastewater-derived biosolids and cattle-derived manure), water reuse, and drinking water systems disrupted by a major hurricane. A field study was carried out to survey a suite of pathogens from source-to tap in six small drinking water systems in Puerto Rico six months after Hurricane Maria. The study revealed that pathogenic Leptospira DNA was detected in all systems that were reliant on surface water. On the other hand, Salmonella spp. was detected in surface and groundwater sources and some distribution system waters both by culture and PCR. The study provided comparison of molecular-, microscopic-, and culture-based analysis for pathogen detection and highlighted the need for disaster preparedness for small water systems, including back-up power supply and access to chlorination as soon as possible after a natural disaster. A second field-study examined wastewater derived solids across an international transect of wastewater treatment plants in order to gain insight into the range of ARG concentrations encountered. It was found that, while total ARGs did not vary between treatment or continent of origin, clinically-relevant ARGs (i.e., ARGs encoding resistance to important classes of antibiotics used in humans) were significantly higher in solids derived from Asian wastewater treatment plants. Estimated loading rates of ARGs to soil under a scenario of land application were determined, highlighting in all cases that they are orders of magnitude higher than in the aqueous effluent. Livestock manure, derived from control cattle and cattle undergoing typical antibiotic treatment, and corresponding composts were also evaluated as common soil amendments in a separate study. In this study, the amendments were applied to two soil types in a greenhouse setting, in order to compare the resulting carriage of ARGs on a root (radish) versus leafy (lettuce) vegetable. Remarkably, radishes were found to harbor the highest relative abundance of total ARGs enumerated by metagenomics, even higher than corresponding soils or manures. Although the total microbial load will be lower on a harvested vegetable, the results suggest that the vegetable surface environment can differentially favor the survival of ARBs. The role of wastewater and water reuse treatment processes in reducing ARB and ARGs was also investigated at field-scale. Two independent wastewater treatment plants both substantially reduced total ARG relative and absolute abundance through biological treatment and settling according to metagenomic analysis. The subsequent water reuse treatment train of one system produced water for non- potable purposes and found further reduction in ARGs after chlorination, but a five hundred percent increase in the relative abundance of ARGs in the subsequent distribution system. In the second plant, which employed a membrane-free ozone-biologically-activated carbon-granular activated carbon treatment train for indirect potable reuse, there were notable increases in total ARG relative abundance following ozonation and chlorination. However, these numbers attenuated below background aquifer levels before recharge. Culture-based analysis of these systems targeting resistant ESKAPE pathogens (Escherichia coil, Staphylococcus aureus, Klebsiella spp., Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterococcus spp.) indicated similar trends as the metagenomic ARG analysis for both systems, but was challenged by sub-optimal media for wastewater samples and low confirmation rates, limiting statistical analysis. In order to advance the application of NGS, molecular, and associated bioinformatic tools for monitoring pathogens and antibiotic resistance in environmental systems, newly emerging methods and field standards for antibiotic resistance assessment were also evaluated. Hybrid assembly, the assembly for both short and long metagenomic sequencing reads, were assessed with an in silico framework in order to determine which available assemblers produced the most accurate and long contigs. Hybrid assembly was found to produce longer and more accurate assemblies at all coverages by reducing error as compared to short read assembly, though the outputs differed in composition from long read assembly. Where it is possible, it is beneficial to sequence using both long- and short-read NGS technologies and employ hybrid assembly, but further validation is recommended. Genome resolved metagenomics has also emerged as a strategy to recover individual bacterial genomes from the mixed metagenomic samples though this is often not well validated. In order to address this, genomes were assembled from reclaimed water systems and were compared against whole-genome sequences of antibiotic resistant E.coli isolates. Metagenome-derived genomes were found to produce similar profiles in wastewater treatment plant influents. A final theme to this dissertation addresses the need to standardize targets, methodologies, and reporting of antibiotic resistance in the environment. A systematic literature review was conducted on assays for the enumeration of key ARGs across aquatic environments and recommendations are summarized for the production of comparable data. In sum, this dissertation advances knowledge about the occurrence of pathogens, ARB, and ARGs across aquatic and agricultural systems and across several countries. Advances are made in the application of NGS tools for environmental monitoring of antibiotic resistance and other targets and a path forward is recommended for continued improvement as both DNA sequencing technologies and computational methodologies continue to rapidly advance.
Beyond Water Regulation: Contamination of Private Wells, Citizen Science, and Corrosion of Household Plumbing
Wait, Kory David (Virginia Tech, 2022-10-19)
The US Safe Drinking Water Act (SDWA), established in 1974, has improved water quality nationwide through the introduction of maximum contaminant levels, source water protection, and treatment guidelines and requirements. Despite the obvious success many important water quality issues are not covered by regulation. These include the following four topics in this dissertation: 1) Support infrastructure for private well users, 2) Identification and analysis of contaminants in private wells, 3) Leaks or corrosion within building plumbing, and 4) The role of citizen scientists in addressing water quality concerns. Private wells, which provide water for approximately 13% of the population (42.5 million people), are not subject to any federal regulation and well users are responsible for ensuring their own water safety. When water quality issues do arise, state or local organizations can provide critically important support. For instance, in North Carolina (NC) local health departments (LHDs) are required to have private well programs that enforce statewide well construction standards, offer water testing services, and provide well water outreach and assistance. Little is known about the effectiveness of such programs, however, so this work conducted a survey of all NC LHDs to determine their capacity for well water outreach and identify differences among programs around the state. All LHDs reported overseeing the construction of new wells as required by law. However, services provided to existing well users were offered infrequently and/or inconsistently offered. Lack of uniformity was observed in the number of LHD staff and their assigned responsibilities; the costs and availability of well water testing; and the comfort of LHD staff communicating with well owners. While the total number of staff was lower in LHDs in rural counties, the number of outreach activities and services offered was typically not related to the number of well users served. Variations in structure and capacity of well programs at LHDs has created unequal access to services and information for well users in NC. Such gaps in NC, which has among the most stringent state guidelines for well water support, suggests the need to examine conditions in other states nationwide. While direct support to private well users is more common at the state and local levels, the scientific information and resources needed by these officials can be supplemented at the federal level or through academia, especially with respect to emerging contaminants, which many officials may not yet have experience with. For instance, following Hurricane Florence in 2018, dam failures and flooding of coal ash disposal and reuse sites in NC prompted concerns about potential contamination of well water with hexavalent chromium. There is also widespread naturally occurring Cr(VI) in the groundwater however, and methods accessible to state and local officials to identify sources are needed. Literature was reviewed related to source tracking techniques and they were applied to Cr(VI) data we collected from 1,265 private wells across 22 NC counties. Almost two thirds of private wells tested (62.0%) exceeded the Cr(VI) public health goal of 0.07 ppb, with concentrations ranging from <0.02-13.9 ppb (median=0.12 ppb). In the literature review, we identified 33 Cr(VI) groundwater tracking techniques from 51 publications and only 5 techniques were used in more than 12 papers. All papers used different combinations of techniques. We applied these techniques to our well sampling data, and inconclusive results were reported for 7 techniques, while three techniques suggested potential geogenic sources whereas three techniques indicated anthropogenic Cr(VI) sources. Specifically looking at coal ash, two techniques did not support coal ash as a primary source and three were inconclusive. Overall, these techniques did not agree as to the origins of Cr(VI) in well water. This may be due to the fact that these techniques primarily focused on regional scale identification, rather than household-level occurrence. This study demonstrates the difficulty and complexity in identifying and distinguishing the source(s) responsible for Cr(VI) in well water. In addition to private wells, another gap in the SDWA framework involves corrosion of plumbing within a home or private building. The Lead and Copper Rule (LCR) was the first SDWA legislation to include sampling at the tap in private buildings, although these results are only used to inform control of the corrosivity of the water at the treatment plant. Thus, there is no maximum level of lead or copper enforced at the consumers tap, and protection against excessive private plumbing corrosion is not required. A survey conducted about a decade ago suggested that recent efforts to increase temperatures of hot water systems to better control Legionella bacteria might also be increasing pinhole leaks in copper plumbing. Recently, an overseas large building experienced at least 300 pinhole leaks in a hot water recirculation system that frequently exceeded > 65°C in 2018. The occurrence of leaks along the top of the pipes where thick deposited of metal oxides were not visibly protective, was not consistent with conventional patterns of failure, but seemed to be a manifestation of an unusual type of hot water pitting due to the presence of cathodic iron or manganese oxide suggested in prior literature. A macro-cell apparatus was developed and tested to mechanistically test this novel hot water pitting corrosion mechanism experimentally. Cathodic manganese oxides deposits were shown to drive pitting corrosion on a part of the pipe surface without deposits. Pitting occurred over a wide range of pH and was worst at a high ratio of sulfate to bicarbonate. While iron oxide coatings tested in this work did not behave cathodically, as suggested in prior literature, further research could determine if some iron oxides might behave similarly to the manganese oxide tested in this work. Past failures to follow provisions of the SDWA has undermined trust in water safety nationally. Collaborations between citizens and scientists can sometimes expose problems with water safety. Over the last decade we have helped consumers evaluated their concerns using citizen science collaborative approaches. We documented and summarized several case studies conducted by the U.S. Water Study team at Virginia Tech that had varying degrees of success in exposing problems with water supplies via citizen science collaborations. The case studies start with a discussion of work in Flint, MI (lead and Legionella bacteria) in 2015 and St. Joseph, LA in 2016 (lead and iron). Later cases included: Enterprise, LA (lead and iron), Denmark, SC (lead, iron, and Halosan), Chicago, IL (lead), Moore, OK (arsenic), Santa Barbara, CA (copper), anonymous town in SC (Acanthamoeba), and Harrisonburg, VA (Legionella). Approaches, challenges and outcomes of each case study are reviewed along with lessons learned. Overall, this dissertation explored water quality issues which, for various reasons, fall outside of the existing SDWA regulatory framework. The importance of well water support was emphasized by documenting inequalities between local health departments well services and by critically reviewing literature to find a lack of scientific guidance for source determination for an important emerging contaminant. Development of a novel apparatus for monitoring of chemistry related hot water pitting allows for a better understanding of this mechanism and provides a baseline of guidance for avoiding or mitigating such problems in the future. Finally, the use of citizen science to address past water quality concerns and that considers reasonable expectations for future work was evaluated.
Bioelectrochemical Systems: Microbiology, Catalysts, Processes and Applications
Yuan, Heyang (Virginia Tech, 2017-11-01)
The treatment of water and wastewater is energy intensive, and there is an urgent need to develop new approaches to address the water-energy challenges. Bioelectrochemical systems (BES) are energy-efficient technologies that can treat wastewater and simultaneously achieve multiple functions such as energy generation, hydrogen production and/or desalination. The objectives of this dissertation are to understand the fundamental microbiology of BES, develop cost-effective cathode catalysts, optimize the process engineering and identify the application niches. It has been shown in Chapter 2 that electrochemically active bacteria can take advantage of shuttle-mediated EET and create optimal anode salinities for their dominance. A novel statistical model has been developed based on the taxonomic data to understand and predict functional dynamics and current production. In Chapter 3, 4 and 5, three cathode catalyst (i.e., N- and S- co-doped porous carbon nanosheets, N-doped bamboo-like CNTs and MoS2 coated on CNTs) have been synthesized and showed effective catalysis of oxygen reduction reaction or hydrogen evolution reaction in BES. Chapter 6, 7 and 8 have demonstrated how BES can be combined with forward osmosis to enhance desalination or achieve self-powered hydrogen production. Mathematical models have been developed to predict the performance of the integrated systems. In Chapter 9, BES have been used as a research platform to understand the fate and removal of antibiotic resistant genes under anaerobic conditions. The studies in this dissertation have collectively demonstrated that BES may hold great promise for energy-efficient water and wastewater treatment.
Bottled and Well Water Quality in a Small Central Appalachian Community: Household-Level Analysis of Enteric Pathogens, Inorganic Chemicals, and Health Outcomes in Rural Southwest Virginia
Cohen, Alasdair; Rasheduzzaman, Md; Darling, Amanda; Krometis, Leigh-Anne H.; Edwards, Marc A.; Brown, Teresa; Ahmed, Tahmina; Wettstone, Erin; Pholwat, Suporn; Taniuchi, Mami; Rogawski McQuade, Elizabeth T. (MDPI, 2022-07-15)
Consumption of unsafe drinking water is associated with a substantial burden of disease globally. In the US, ~1.8 million people in rural areas lack reliable access to safe drinking water. Our objective was to characterize and assess household-level water sources, water quality, and associated health outcomes in Central Appalachia. We collected survey data and water samples (tap, source, and bottled water) from consenting households in a small rural community without utility-supplied water in southwest Virginia. Water samples were analyzed for physicochemical parameters, total coliforms, E. coli, nitrate, sulfate, metals (e.g., arsenic, cadmium, lead), and 30+ enteric pathogens. Among the 69% (n = 9) of households that participated, all had piped well water, though 67% (n = 6) used bottled water as their primary drinking water source. Total coliforms were detected in water samples from 44.4% (n = 4) of homes, E. coli in one home, and enteric pathogens (Aeromonas, Campylobacter, Enterobacter) in 33% (n = 3) of homes. Tap water samples from 11% (n = 1) of homes exceeded the EPA MCL for nitrate, and 33% (n = 3) exceeded the EPA SMCL for iron. Among the 19 individuals residing in study households, reported diarrhea was 25% more likely in homes with measured E. coli and/or specific pathogens (risk ratio = 1.25, cluster-robust standard error = 1.64, p = 0.865). Although our sample size was small, our findings suggest that a considerable number of lower-income residents without utility-supplied water in rural areas of southwest Virginia may be exposed to microbiological and/or chemical contaminants in their water, and many, if not most, rely on bottled water as their primary source of drinking water.
Calcium Carbonate Formation in Water Distribution Systems and Autogenous Repair of Leaks by Inert Particle Clogging
Richards, Colin Scott (Virginia Tech, 2016-06-20)
The formation of calcium carbonate (CaCO3) (i.e. scale) in potable water systems has long been a concern in water treatment and distribution. A literature review reveals that CaCO3 scaling issues are re-emerging due to climate change, temperature increases in hot water systems and lower use of scaling and corrosion inhibitors. Moreover, we have gathered insights that suggest CaCO3 coatings can be beneficial and stop pipeline leaks via self-repair or clogging. Ironically, the actions we are taking to increase the lifespan of distribution systems (i.e. adding corrosion inhibitors) might have worsened leaks and pipe lifespans due to interference with self-repair. The increasing occurrence of scaling coupled with gaps in knowledge over CaCO3 formation in water systems make revisiting this topic timely. The concept of autogenous repair by clogging with inert particles was examined using silica and alumina. Small 250 m diameter pinhole leaks were simulated in bench-scale water recirculation systems. Silica and alumina particles were added to solutions ranging from high to low ionic strength to determine the impact of water quality on leak repair. Size distribution and zeta potential of the particles were measured. Silica particles were practically unchanged by the different solution chemistries while the size and zeta potential of alumina particles varied. The rate of clogging with silica particles was not impacted by water chemistry. Alumina particles with a positive charge clogged 100% of the leaks while negatively charged alumina could not clog 100%. Very small alumina particles (4.1 m) stayed suspended but were unable to clog leaks.
Cavitation and Bubble Formation in Water Distribution Systems
Novak, Julia Ann (Virginia Tech, 2005-04-08)
Gaseous cavitation is examined from a practical and theoretical standpoint. Classical cavitation experiments which disregard dissolved gas are not directly relevant to natural water systems and require a redefined cavitation inception number which considers dissolved gases. In a pressurized water distribution system, classical cavitation is only expected to occur at extreme negative pressure caused by water hammer or at certain valves. Classical theory does not describe some practical phenomena including noisy pipes, necessity of air release valves, faulty instrument readings due to bubbles, and reports of premature pipe failure; inclusion of gaseous cavitation phenomena can better explain these events. Gaseous cavitation can be expected to influence corrosion in water distribution pipes. Bubbles can form within the water distribution system by a mechanism known as gaseous cavitation. A small scale apparatus was constructed to track gaseous cavitation as it could occur in buildings. Four independent measurements including visual observation of bubbles, an inline turbidimeter, an ultrasonic flow meter, and an inline total dissolved gas probe were used to track the phenomenon. All four measurements confirmed that gaseous cavitation was occurring within the experimental distribution system, even at pressures up to 40 psi. Gaseous cavitation was more likely at higher initial dissolved gas content, higher temperature, higher velocity and lower pressure. Certain changes in pH, conductivity, and surfactant concentration also tended to increase the likelihood of cavitation. For example, compared to the control at pH 5.0 and 30 psig, the turbidity increased 295% at pH 9.9. The formation of bubbles reduced the pump's operating efficiency, and in the above example, the velocity was decreased by 17% at pH 9.9 versus pH 5.0.
Challenges of Detecting Lead in Drinking Water Using at-Home Test Kits
Kriss, Rebecca; Pieper, Kelsey J.; Parks, Jeffrey L.; Edwards, Marc A. (2021-02-02)
Lead in drinking water remains a significant human health risk. At-home lead in water test kits could provide consumers with a convenient and affordable option to evaluate this risk, but their accuracy and reliability is uncertain. This study examined the ability of at-home lead test kits to detect varying concentrations of dissolved and particulate lead in drinking water. Sixteen brands representing four test kit types (binary color, binary strip, colorimetric vial, and color strip) were identified. Most kits (12 of 16 brands) were not suitable for drinking water analysis, with lead detection limits of 5-20 mg/L. Binary strips detected dissolved lead at drinking water-relevant levels but failed to detect particulate lead. Household acids (lemon juice and vinegar) improved the strip's ability to detect lead by dissolving some of the lead particulates to the point soluble lead exceeded 15 mu g/L. These results illustrate the applications of at-home testing kits for drinking water analysis, highlight limitations and areas for possible improvement, and put forth a testing protocol by which new at-home lead test kits can be judged.
Characterization of Magnetite Nanoparticle Reactivity in the Presence of Carbon Tetrachloride
Heathcock, April Marie (Virginia Tech, 2006-07-24)
Throughout the United States, there are a large number of groundwater systems contaminated by chlorinated organic compounds. Of these compounds, carbon tetrachloride (CT) is one of the most frequently encountered due to its past, widespread industrial use. In anaerobic groundwater environments, CT has been shown to be susceptible to degradation by both biotic and abiotic processes. One abiotic process that has been researched extensively is the reduction of CT by iron metal and associated iron oxides and hydroxides. Magnetite, an iron oxide, is a ubiquitous component of many subsurface environments and has been investigated as a potential groundwater remediation technology. One beneficial characteristic of magnetite is the capability to be synthetically produced in various sizes and shapes - including particles within the nanoscale range. Nanoscale particles have been shown to be more reactive towards contaminants than larger sized particles due to their large surface areas and high surface reactivity. This project was designed to characterize the behavior of synthetic magnetite in the presence of carbon tetrachloride under anaerobic conditions.
Characterization of opportunistic Pathogens in Drinking Water Supplied by Private Wells
Mapili, Kristine Irene Manzano (Virginia Tech, 2019-07-03)
Private wells are understudied potential sources of opportunistic pathogen (OP) infections. OPs, including Legionella and Mycobacterium, are of particular concern for immunocompromised individuals and are known to proliferate in drinking water systems. Much of our knowledge surrounding OP occurrence and growth in drinking water relates to municipal drinking water systems, which primarily use surface water sources and are always treated with primary and secondary disinfection in United States. However, OP occurrence and growth in private wells is not well understood and it is unclear how the knowledge developed in municipal systems will translate to private well systems with rare and infrequent exposure to chemical disinfectants. In addition, because private wells are more susceptible to microbial contamination than municipal systems, the impact of flooding on OP occurrence is of particular concern. Two private well field surveys were conducted to document the incidence of OPs in private well systems. One survey conducted in North Carolina private wells with no history of recent flooding was focused on molecular and culture-based detection of Legionella spp. and Legionella pneumophila. The other survey was a broader molecular (i.e., DNA-based) characterization of the incidence of Legionella spp., L. pneumophila, Mycobacterium spp., Mycobacterium avium (the most commonly nontuberculous mycobacteria associated with disease), and Naegleria fowleri in private wells with recent history of flooding (i.e., Hurricanes Harvey and Irma in 2017, or the Great Louisiana Floods in 2016, extending to Texas, Florida, and Louisiana). All samples in both studies were analyzed for total bacterial 16S rRNA genes, indicator bacteria (e.g., total coliform and Escherichia coli) and inorganic constituents. Information about well system characteristics were obtained through questionnaires sent to participating residents. Widespread detection of OP DNA markers were noted in the flooded well survey. Legionella spp. (detectable in 50-100% of well waters, depending on the flood event) and Mycobacterium spp. (detectable in 13.2-45.0% of well waters) were the most commonly detected among the OPs targets. At the genus level, L. pneumophila (7.9-65.5%) and M. avium (7.9-32.5%) were less commonly detected, but still highly variable. It is not possible to judge whether these OP levels were elevated as a result of the flooding because the sampling was carried out as an emergency response and background levels were not previously tested. Also of interest was whether well characteristics could predict OP levels, including well depth, well type, or treatment. However, none of these emerged as significant predictors of OP detection frequency or levels. Similarly, these OP DNA markers were not elevated in homes reporting submerged wellheads or system damage, suggesting that detection of these OPs is more dependent on the groundwater that supplies these private wells than influx of contaminated surface water. The incidence of DNA markers pertaining to N. fowleri, the "brain eating amoeba" that causes rare incidences of primary amebic meningoencephalitis (PAM), tended to be lower (5.0-12.7%) than that of other OPs targeted, but was more frequently detected in wells reporting submerged well heads, suggesting its occurrence was related to contamination from flood water. A positive association between total bacteria and occurrence of both Legionella spp. and Mycobacterium spp., was observed in private wells of all surveyed areas, contrary to observations in municipal drinking water systems with secondary disinfectant residuals. On the other hand, Legionella reportedly has an optimal growth range of 20-42 °C in municipal systems and recent surveys of municipal systems reported a strong association between Legionella spp. and temperature that was not observed for private wells in this study. We speculate that the essentially "infinite" water age and lack of disinfectant for well water, may contribute to these differences relative to municipal water supplies. The results presented in this work are likely an overestimation of OPs numbers in private wells, as molecular detection of OPs does not distinguish between live and dead cells. In addition, sample sizes were limited by laboratory throughput and budget. Identifying key variables impacting the occurrence of OPs in private wells, given that our study shows that these pathogens are relatively common, might someday help limit the risk of infections.
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.

Browsing by Author "Edwards, Marc A."

Results Per Page

Sort Options