Browsing by Author "Parks, Jeffrey L."
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- Challenges of Detecting Lead in Drinking Water Using at-Home Test KitsKriss, 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.
- Effectiveness of Prevailing Flush Guidelines to Prevent Exposure to Lead in Tap WaterKatner, Adrienne; Pieper, Kelsey J.; Brown, Komal; Lin, Hui-Yi; Parks, Jeffrey L.; Wang, Xinnan; Hu, Chih-Yang; Masters, Sheldon; Mielke, Howard; Edwards, Marc A. (MDPI, 2018-07-20)Flushing tap water is promoted as a low cost approach to reducing water lead exposures. This study evaluated lead reduction when prevailing flush guidelines (30 s–2 min) are implemented in a city compliant with lead-associated water regulations (New Orleans, LA, USA). Water samples (n = 1497) collected from a convenience sample of 376 residential sites (2015–2017) were analyzed for lead. Samples were collected at (1) first draw (n = 375) and after incremental flushes of (2) 30–45 s (n = 375); (3) 2.5–3 min (n = 373), and (4) 5.5–6 min (n = 218). There was a small but significant increase in water lead after the 30 s flush (vs. first draw lead). There was no significant lead reduction until the 6 min flush (p < 0.05); but of these samples, 52% still had detectable lead (≥1 ppb). Older homes (pre-1950) and low occupancy sites had significantly higher water lead (p < 0.05). Each sample type had health-based standard exceedances in over 50% of sites sampled (max: 58 ppb). While flushing may be an effective short-term approach to remediate high lead, prevailing flush recommendations are an inconsistently effective exposure prevention measure that may inadvertently increase exposures. Public health messages should be modified to ensure appropriate application of flushing, while acknowledging its short-comings and practical limitations.
- Effects of Scale Reduction Technologies and Chemical Inhibitors on Calcium Precipitation in Premise Plumbing SystemsDevine, Christina Laura (Virginia Tech, 2021-04-14)Precipitation of solids in plumbing systems (i.e., scaling) is a major problem in both traditional tank (electric and gas) and tank-less building hot water systems. Scaling can cause energy inefficiencies, flow reduction, pressure loss, and erosion corrosion damage. Consumers are also concerned with unsightly soap scum, cloudy water, discolored glassware, and failing infrastructure including appliances and fixtures. There are many treatments available that claim to ameliorate scaling problems, and several efforts have been made to develop standardized test protocols to verify and quantify their performance. This work critically evaluated previous testing efforts and revealed limitations in terms of reproducibility and a need to measure all key aspects of scale deposition including quantity, location, aesthetic and other issues. A Standardized Scaling Test Protocol (SSTP) was conceived and vetted to address these deficiencies and measure key parameters of calcium carbonate scaling throughout a model premise plumbing system, while using a synthesized test water that could provide reproducible results in any laboratory. This synthetic water and methodology was able to produce significant scaling in a model hot water system within the targeted 5-day experimental time frame. The average amount of scale recovered for the triplicate control tests (with no scale reduction device) was 25.1 grams of calcium carbonate with a 95% confidence interval of 20.3-29.8 grams of calcium carbonate. The approach also worked in recreating scaling in natural waters and was used to verify the performance of a wide array of scale reduction technologies including cation exchange softeners, electrochemical deionization, physical magnets or electric field generators, media induced precipitation, sacrificial media (phosphate), and sacrificial media (citric acid). While calcium carbonate precipitation within a water distribution system is generally undesirable; it was recently discovered that calcium carbonate particles are sometimes naturally clogging leaks in pipes and extending the lifetime of aging infrastructure. Corrosion inhibitors, mainly phosphates, have been increasingly dosed (up to 3.0 mg/L as PO4) into water to inhibit the corrosion of lead and copper pipelines in potable water systems since the advent of the Lead and Copper Rule (LCR) in 1991 by US Environmental Protection Agency (EPA). Phosphate corrosion inhibitors are now used at over 50% of water utilities in the United States and they can affect calcium carbonate scaling kinetics. In bench-scale experiments, the critical concentrations of phosphates that could inhibit leak repair over the short-term in one water tested were: tripolyphosphate (0.05 mg/L as P) < hexametaphosphate (0.1 mg/L) < orthophosphate (0.3 mg/L). The results prove that dosing of phosphates for corrosion control will also affect the kinetics and likelihood of calcium carbonate precipitation, with both beneficial and adverse consequences for pipes and consumers. Specifically, increased use of inhibitors for corrosion control is expected to reduce the likelihood of all calcium carbonate scaling problems while reducing the likelihood of autogenous pipe leak repair. In Providence, RI the dosing of orthophosphate at relatively high pH to control a lead corrosion problem, caused formation of a white precipitate, consumer reports of white water, clogging of aerators and loss of the added soluble phosphate corrosion control inhibitor due to precipitation. The precipitate was identified as a calcium phosphate solid. Field and lab scale tests suggest that at doses below 2 mg/L as PO4, precipitation did not occur in water at pH 10.4 even when the water was heated to 48°C. However, if the water was dosed above 2 mg/L as PO4 precipitation occurred within 5 minutes, and once pre-existing particles were formed precipitation tended to continue even at much lower phosphate doses. Virtually all of the phosphate precipitated within 4 hours at the upper range of 60°C that is commonly found in water heaters. Thus, dosing of phosphate can actually increase scaling problems in some circumstances. Prior work has highlighted a need for a simplified bench-scale test that can be used to rapidly screen for qualitative trends in scaling. The SSTP and practical experience showed that the vast majority of scaling occurred in the water heater. Therefore, a simplified bench-scale test consisting of a heating element in a small volume of water could be used to focus on the most sensitive aspect of scaling. A 3-hour bench-scale test was developed to quickly examine scaling with orders of magnitude less volume, time, labor, cost, and space requirements. This approach was used to evaluate aspects of scaling in water heaters for the following illustrative examples: (1) scale impacts of combined phosphate corrosion inhibitor addition and partial water softening at centralized treatment plants, (2) role of silica concentration in scaling propensity and deposit durability, (3) effects of phosphate addition on scaling in a water known to cause erosion corrosion pipe damage. This dissertation reveals the complexity of scaling for consumers and water utilities and provides tools to systematically study and resolve these practical problems. Dosing of phosphate corrosion control inhibitors can increase scaling from calcium phosphate, decrease scaling of calcium carbonate, and in other cases will have little or no effect on scaling. Both calcium carbonate and calcium phosphate can contribute to scaling as controlled by pH, temperature, hardness, phosphate dose, and other circumstances. The standardized bench and pilot scale approaches developed herein, can serve as a basis for building knowledge reproducibly in any modern laboratory. These methods can also be used to verify performance claims for a wide range of scale reduction technologies, test treatments that could be applied at centralized treatment plants, and optimize water heater design dependent on water chemistry.
- Evaluating Leachability of Residual Solids Generated from Unconventional Shale Gas Production Operations in Marcellus ShaleSharma, Shekar (Virginia Tech, 2014-09-17)Hydraulic fracturing operations utilized for shale gas production result in the generation of a large volume of flowback and produced water that contain suspended material, salts, hydrocarbons, metals, chemical additives, and naturally-occurring radioactive material. The water is impounded at drilling sites or treated off-site, resulting in significant generation of residual solids. These are either buried on site or are disposed in lined landfills. The objective of this study was to determine the levels of heavy metals and other elements of concern that will leach from these residual solids when placed in typical disposal environments. For this purpose, laboratory leaching experiments were employed wherein representative samples were brought into contact with a liquid to determine the constituents that would be leached by the liquid and potentially released into the environment. The samples used included sludge resulting from the physicochemical treatment of process water (TS), sludge solidified with cement kiln dust (SS), raw solids obtained by gravity separation of process water (RS), and drilling mud (DM). The samples were subjected to both single extraction (i.e. Shake Extraction Test, SET) and multiple extraction (i.e. Immersion Test, IT) leaching tests. For the shake extraction test, samples were mixed with a specific amount of leaching solution without renewal over a short time period. In the immersion test, samples were immersed in a specific amount of leaching solution that was periodically renewed over a longer period of time. For both these tests, analyses were performed on the filtered eluate. The tests were performed as per standards with modifications. Distilled de-ionized water, synthetic acid rain (pH ~ 4.2), weak acetic acid (pH ~ 2.88), and synthetic landfill leachate were used as leaching solutions to mimic specific disposal environments. Alkali metals (Li, K, Na), alkaline earth metals (Ba, Ca, Mg, Sr) and a halide (Br), which are typically associated with Marcellus shale and produced waters, leached at high concentrations from most of the residual solids sample. The SS sample, due to its stabilization with CKD, had a lower extraction efficiency as compared to the unconsolidated TS and RS samples. In EF 2.9 and EF SLL, the leaching took place under acidic conditions, while for EF DDI and EF 4.2, the leaching occurred in alkaline conditions. EF 2.9 and EF SLL were determined to be the most aggressive leaching solutions, causing the maximum solubility of most inorganic elements. Thus, high amounts of most EOCs may leach from these residual solids in MSW landfills disposed under co-disposal conditions. Agitation, pH and composition of the leaching solution were determined to be important variables in evaluating the leaching potential of a sample. The results of this study should help with the design of further research experiments being undertaken to develop environmentally responsible management/disposal strategies for these residual solids and also prove useful for regulatory authorities in their efforts to develop specific guidelines for the disposal of residuals from shale gas production operations.
- Evaluating the Leachability of Elements from Residuals Generated by Hydraulic Fracturing in Marcellus ShaleSwann, Christina Talbot (Virginia Tech, 2015-06-25)The purpose of this research was to characterize the residual solids produced from hydraulic fracturing operations in the Marcellus Shale region. Four field samples were evaluated: drilling mud, treated sludge from the chemical treatment of process water, solids from the gravity settling of produced water, and sludge solidified prior to disposal in a municipal landfill. Cement kiln dust (CKD), used for solidification, was also considered in this study. All samples were subjected to a variety of laboratory techniques to determine their elemental composition and the potential for the elements to leach from the landfill. Strong acid digestion using a 3:1 combination of nitric acid to hydrochloric acid in a microwave with closed vessels was used to determine overall elemental composition. Leaching experiments were performed with de-ionized water and acetic acid (0.57%, pH 2.88) in an attempt to respectively evaluate the effects of weak and strong fluids that might be encountered by the residuals in landfill environments. Elements were analyzed by means of ICP-MS revealing the increased tendency for alkali metals, alkaline earth metals and halogens to leach. Leachablility was further increased for metals when exposed to acidic conditions.
- Evaluating Water Lead Levels During the Flint Water CrisisPieper, Kelsey J.; Martin, Rebekah L.; Tang, Min; Walters, LeeAnne; Parks, Jeffrey L.; Roy, Siddhartha; Devine, Christina; Edwards, Marc A. (ACS, 2018-06-22)In April 2014, the drinking water source in Flint, Michigan was switched from Lake Huron water with phosphate inhibitors to Flint River water without corrosion inhibitors. The absence of corrosion control and use of a more corrosive source increased lead leaching from plumbing. Our city-wide citizen science water lead results contradicted official claims that there was no problem– our 90th percentile was 26.8 μg/L, which was almost double the Lead and Copper Rule action level of 15 μg/L. Back calculations of a LCR sampling pool with 50% lead pipes indicated an estimated 90th percentile lead value of 31.7 μg/L (±4.3 μg/L). Four subsequent sampling efforts were conducted to track reductions in water lead after the switch back to Lake Huron water and enhanced corrosion control. The incidence of water lead varied by service line material. Between August 2015 and November 2016, median water lead reduced from 3.0 to <1 μg/L for homes with copper service lines, 7.2–1.9 μg/L with galvanized service lines, and 9.9–2.3 μg/L with lead service lines. As of summer 2017, our 90th percentile of 7.9 μg/L no longer differed from official results, which indicated Flint’s water lead levels were below the action level.
- Evaluation of Zinc Orthophosphate to Control Lead Solder Corrosion in Waters With High Chloride to Sulfate Mass RatioBradley, Taylor Nicole (Virginia Tech, 2018-03-28)Chloride levels are increasing in some water supplies around the country due to use of road salts and seawater intrusion, which can increase the chloride-to-sulfate mass ratio (CSMR) and trigger serious water lead contamination from galvanic lead solder: copper pipe corrosion. Previous attempts to control this problem through simple water chemistry modifications were unsuccessful, but in this work a combination of zinc orthophosphate and moderate alkalinity mitigated lead release in testing at two utilities. Either zinc alone or phosphate alone were irrelatively ineffective, but the combination of zinc orthophosphate reduced lead leaching by 54-99% (compared to the control without inhibitors) if alkalinity was above about 55 mg/L as CaCO3. These results may help mitigate future lead in water contamination events.
- Phosphate use for Sequestration, Anti-Scaling, and Corrosion Control: Critical Review, Simultaneous Optimization of Polyphosphate Dosing, Sequestration Mechanisms, and Stabilization of Magnesium Silicate ScaleLytle, Christian J. (Virginia Tech, 2024-07-01)Phosphates are used by drinking water utilities to 1) reduce iron/manganese aesthetic problems by sequestration, 2) inhibit calcium carbonate scale formation via threshold inhibition, and 3) reduce corrosion of pipes by forming protective pipe scales. Orthophosphates can control lead, copper and iron corrosion through the formation of durable, low solubility scale, but are widely believed ineffective for sequestration or anti-scaling. Conversely, polyphosphates are effective sequestrants and anti-scalants, but can increase corrosion of plumbing materials. Here, we first critically reviewed the current state of the science, operational guidance, and knowledge gaps related to use of orthophosphate and polyphosphates for all three objectives. Three major gaps in understanding were identified and then addressed in subsequent chapters: 1) use of phosphates to achieve both sequestration and anti-scaling 2) mechanisms of iron sequestration, and 3) stabilization of magnesium silicate scale linings in a distribution system. In the critical review, we holistically conceptualize phosphate use as a three-dimensional (3-D) challenge of optimizing sequestration, anti-scaling and corrosion control. Despite nearly a century of widespread use, there is a poor scientific and practical understanding of how to use phosphates to achieve each of these key objectives, much less achieve synergies and avoid antagonistic effects. Many water systems are reliant on trial-and-error methods, or guidance from vendors of these proprietary chemicals, creating potential inefficiencies or even adverse unintended consequences. Effective sequestration of iron and manganese, to prevent formation of visible discoloration, can occur through four possible mechanisms which are undoubtedly dependent on the water chemistry (e.g., pH, hardness, redox). Anti-scaling of calcium carbonate occurs through threshold inhibition and crystal distortion, but sometimes phosphates can encourage scaling due to the precipitation of calcium phosphate. Corrosion control via orthophosphate is often effective, but polyphosphates can sometimes increase lead or copper levels in drinking water. Despite their widespread use in scientific studies, it was discovered that standardized measurements of color and turbidity do not fully account for the range of subjective consumer observations regarding cloudy or discolored water. At a constant apparent color of 110 Pt-Co, testing illustrated that relatively non-offensive air bubbles had a high turbidity of 74 NTU compared to just 0.1 NTU for offensively orange fulvic acid. Additionally, factors such as background color, type of light source, and direction of light significantly influenced perception of discolored water. For instance, under typical laboratory lighting conditions (light from above) with a white background, colors caused by iron, manganese, and fulvic acid were very prominent, whereas white calcium carbonate and magnesium silicate particles were more challenging to see. But white particles became much more prominent when the light source was from below or there was a darker background. A study of Fe sequestration was conducted to elucidate a mechanistic basis for the empirical trends revealed in the utility field study. As revealed in the literature review, polyphosphates could sequester Fe by inhibiting any step of the reaction sequence Fe2+ oxidation precipitation of Fe(OH)3 particle agglomeration to visible sizes. Phosphates generally inhibited Fe2+ oxidation above about pH 7-8, dependent on chain length, and catalyzed oxidation at lower pHs. But in oxygenated waters above about pH 7, the dominant mechanism of sequestration was some combination of Fe3+ complexation and colloid stabilization at small particle sizes that were practically invisible. Increasing the phosphate chain length, phosphate concentration, and Si concentration caused more effective Fe sequestration, whereas Ca, Mg, and increased pH hindered its effectiveness. It was also discovered that orthophosphate can be an effective sequestrant under ideal conditions, polyphosphate can sequester more than 1 mg/L Fe despite some claims to the contrary, and Ca at very high doses can precipitate polyphosphates. During this dissertation work, a novel, thick (~1 mm), glassy magnesium silicate (MgSi) scale was discovered covering much of the pipe surfaces in a large water distribution system. This MgSi lining was hypothesized to be an extremely effective means of corrosion control that was important to maintain in its present state, as dissolution could cause it to detach from pipes, whereas further precipitation could clog them. To better understand how to maintain the scale, factors affecting the formation and dissolution of the MgSi solid were examined. Phosphate corrosion inhibitors had little effect on MgSi solubility at pH 8.5 and 10, while hexametaphosphate (HMP) and zinc orthophosphate slightly reduced Mg and Si dissolution rates at pH 7. Zinc orthophosphate reduced Mg dissolution by 50% and completely inhibited Si dissolution from the solid, while HMP decreased dissolution of Mg by 32% and Si by 63%. The magnesium silicate did not precipitate below pH 10 without the presence of a pre-existing seed solid. With a pre-existing seed scale, however, the MgSi further precipitated at a pH 8.5-9 in one source water and 7.5-8 in another. Below these pH levels, scale dissolution was shown to occur. Strategies were evaluated to help identify the equilibration pH for operation of a system with varying concentrations of silica, magnesium and pH. The two-dimensional (2-D) interplay of polyphosphate use for sequestration and anti-scaling was investigated for nine small utilities who rely on groundwater in North Carolina. Bench-top testing methods were developed to determine the 'optimal phosphate doses,' defined here as the lowest level of polyphosphate that maintains visually clear water and acceptable levels of scale formation. One proprietary polyphosphate chemical had an optimal sequestrant dose that depends on the concentration of Fe, Mn, Ca, and Mg. The dose (in mg/L as P) is equal to 58.5[Fe] + 59.7[Mn] + 0.041[Ca + Mg] + 0.4669 (units mM). Interestingly, color was well correlated with particulate (> 0.45 μm) Mn (R2 = 0.79) while turbidity was mostly correlated with particulate iron (R2 = 0.60). Furthermore, neither color nor turbidity measurements were reliable predictors of discoloration detected by eye. In the three utilities with higher hardness (> 100 mg/L as CaCO3), at least 3.6X more phosphate was needed for Fe and Mn sequestration than scale inhibition. But lab testing in very hard water with 300 mg/L as CaCO3 demonstrated that achieving anti-scaling, will sometimes require more polyphosphate than that needed for control of sequestration. Overall, this dissertation advances understanding of phosphate use in relation to important problems arising in water distribution or buildings. The innovative practical testing methods, improved practical understanding, and mechanistic insights can be applied to maximized the benefits of phosphates use while avoiding detriments. This is an important first step towards developing a rational holistic framework to guide utility decision-making regarding phosphate use.
- Physiochemical Treatment Options for High-Conductivity Coal Mining RunoffGrey, Catherine Vyvian (Virginia Tech, 2017-03-22)In recent years, the excessive specific conductance (SC) of Appalachian coal mining runoff waters has become a parameter of concern with the EPA due to its negative effect on aquatic life and water quality. In order to comply with the EPA guidance suggesting an effluent SC of 500 µS/cm, the Appalachian Research Initiative for Environmental Science (ARIES) Center at Virginia Tech requested that testing be done to determine the most effective technologies for reduction of SC. Runoff water was collected from two sites in southwestern Virginia and characterized to determine the source of SC in the water. The main contributing ions were determined to be Na⁺, Mg²⁻, Ca²⁺, and SO₄²⁻. Testing was performed to assess the possibility of using the speciation software, MINEQL+, with a set of empirical equations which predict SC using ionic composition for natural waters with a low to medium SC. The physicochemical treatment methods tested were ion exchange, excess lime-soda softening, and the Cost Effective Sulfate Removal (CESR) process. Both cation (H⁺ exchanger) and anion (Cl⁻ exchanger) exchange media were tested separately in batch reactors, which resulted in a higher effluent SC than initial SC. The softening method investigated, excess lime-soda softening, also resulted in increased SC levels because non-carbonate hardness levels were high and carbonate concentrations were low. The CESR process successfully lowered SC from 1,500-2,500 µS/cm to below the proposed EPA limit of 500 µS/cm. The success of this process was due to its ability to remove more than 85% of the calcium, magnesium, and sulfate from the water, which together accounted for more than 90% of ions in the source water.
- Practical Application of NSF/ANSI 53 Lead Certified Filters: Investigating Lead Removal, Clogging and Consumer ExperiencePurchase, Jeannie Marie (Virginia Tech, 2022-02-17)NSF/ANSI 53 lead-certified point-of-use filters (POUs) have been distributed to consumers in many cities facing water lead crises, including Washington D.C., Flint, MI, Newark, NJ, and University Park, IL. It is expected that these filters would reduce water lead to levels that are safe for consumption as residents wait for municipalities to provide more permanent solutions (e.g., corrosion control, lead service line replacement). These filters are certified by the National Sanitation Foundation (NSF) after meeting the challenges of treating two lab synthesized waters with 150 μg/L of soluble and particulate lead. In Flint, as in Washington, there were initial concerns that the filters would not be effective when exposed to lead levels far above the NSF/ANSI 53 150 μg/L Pb level used for certification. However, the EPA conducted a 2016 study in Flint, MI, with over 240 homes with lead up to 4080 μg/L, revealing that all POUs reduced lead levels below 1 μg/L. Newark, NJ, in response to Lead and Copper Rule (LCR) violations, distributed over 40,000 NSF/ANSI 53 lead-certified pitcher and faucet POUs to protect consumers from high water lead levels. In the summer of 2019, preliminary tests in some homes with the highest lead in water concentrations revealed that 2 of 3 POUs used in Newark had effluent lead levels above 15 μg/L. The publication of these results caused citywide angst, distrust, and EPA mandated a switch to bottled water. However, a later and more extensive study revealed that 97.5% of homes (n=198) with properly used filters had effluent lead levels below 10 μg/L. As a result, the EPA approved Newark's request to discontinue bottled water distribution and only provide POUs to residents. Nevertheless, the experience indicated that it is vital to understand the limitations of POUs. This dissertation comprises three manuscripts that examine the efficacy of POUs under laboratory and field conditions. The first manuscript sought to provide perspective into potential causes of the filter failures observed in the field. We conducted an extensive laboratory investigation that examined the performance of 10 pitcher and faucet POU brands under extreme conditions (e.g., up to 200% of rated capacity, influent lead levels ≈ 1000 μg/L). Our tests confirmed successful performance documented in some field testing and replicated underperformance observed in others. In this investigation, we observed structural failures due to poor manufacturing (i.e., leaking units, a filter with a large hole in the media) and performance failures (filtered water >10 μg/L Pb). Some of the performance failures occurred when we tested particulate lead waters, which we created, proving to be very difficult to treat relative to those used for NSF/ANSI testing. While the POUs almost always reduce consumer lead exposure, even when operated beyond their rated capacity, this study highlights instances where treated water could far exceed 10 μg/L lead. High particulate iron (Fe) and manganese (Mn) concentrations often co-occur with high lead in many low-income, rural communities with small community water systems (CWS) or in homes with private wells. These communities are more likely to depend on POUs for protection from waterborne lead as they typically do not have the funds to maintain and upgrade infrastructure, improve corrosion control, or replace service lines. Waters with high levels of Fe and Mn could potentially impact the performance of the POU lead filters. However, such problems would not be detected in NSF/ANSI certification testing because these constituents are not included within the test water. The second manuscript validated anecdotal reports of premature POU failure due to clogging in rural communities with high iron concentrations in their water. POU pitcher filters were tested with waters containing high lead and iron up to 100% of their rated capacity, or until they clogged as defined by a 75% reduction in initial flowrate. Iron levels above the 0.3 mg/L Secondary Maximum Contaminant Level (SMCL) resulted in rapid clogging, markedly increasing treatment costs, and decreasing consumer satisfaction. At 0.3 mg/L Fe, half of the 6 POU filters tested were clogged at between 38-68% of their rated capacity. When considering the cost of using POU filters vs. purchasing bottled water, the POU devices were often more cost-effective at iron levels at or below 0.3 mg/L. However, as iron concentrations increased, bottled water often became cost-effective depending on the circumstance. The presence of iron did not have an adverse effect on lead removal but significantly affected the cost and reduced flow rates in treating water. The third manuscript presents a two-phase field study that sought to monitor the long-term filter performance in residential homes in New Orleans and Enterprise, LA. Previous field studies have captured POU removal efficiencies in single event (grab) samples; however, this study quantified filter performance for all the water treated up to POU practical capacity (i.e., filter life) based on consumer judgment regarding acceptable flow rate. The first phase was a rigorously controlled study that tested the POUs (100-gal capacity) at up to 200% of their rated capacity in two New Orleans unoccupied homes. Historically, the first home had consistently high lead levels (10-25 μg/L) even after flushing for > 8 min. Duplicate POUs treated that water to below 5 μg/L at up to 100% capacity, with only two exceptional samples with 12 μg/L Pb in 10-gallon batches of the treated water. The second home had a disturbed lead service line (LSL), resulting in varying concentrations of influent particulate lead ranging from 9-3000 μg/L. The duplicate POUs had difficulty producing water lead levels <10 μg/L before reaching filter capacity, with eight exceedances prior to 100% capacity. This work demonstrated that flushing alone for extended periods (>8 minutes) is not guaranteed to reduce lead levels in all homes with LSLs and highlights some limitations of POU filters in treating water with high levels of particulate lead. The second phase of the field study monitored POU faucet filter performance in the homes of 21 residents in New Orleans (8) and Enterprise (13), LA. New Orleans is a large urban area with low to moderate water lead levels with many partial LSL replacements. Enterprise (population <300) is a rural, low-income community with an unincorporated water system with moderate to high water lead, iron, and manganese levels. Overall, the POUs consistently reduced lead to <1 μg/L, iron <171 μg/L, and manganese <180 μg/L. Enterprise's high influent concentrations of iron significantly impacted filter capacity due to reduced flow and clogging. Enterprise homes saw an average 62% flowrate reduction, and most of the homes did not reach 50% of the filter's rated capacity before consumers decided the filters were clogged. Most New Orleans residents did not experience clogging, and the homes that did saw only a 16% flow rate reduction. Overall, the New Orleans POUs were 2.3X faster in treating water by the study's end than Enterprise. There was no simple correlation between average iron concentration and days of filter life amongst residents in Enterprise as would be expected given variations in the volume of water used daily and consumer subjectivity in deciding when to end the study due to clogging. However, residents in Enterprise and similar communities would likely need to purchase 2-4 times as many filter cartridges due to clogging when compared to cities like New Orleans with lower iron concentrations. This study shows how POUs have promise for the removal of Pb and Fe in residential homes, but clogging has emerged as an important practical limitation to widespread successful POU deployment. This dissertation highlighted the multifaceted nature of the question: "How well do POU filters work and under what conditions?" Overall, the POUs have shown their ability to reduce water lead levels effectively <5 μg/L, with a few exceptions primarily attributed to particulate lead and manufacturing quality control issues. However, when treating waters with high levels of iron and other contaminants, POU clogging can cause consumer dissatisfaction and make purchasing bottled water a more favorable solution than POU filters.
- Role of Chloride in Galvanized Iron Plumbing Corrosion and the Use of Fingerprinting Methods to Identify Water Lead SourcesMohsin, Hisyam (Virginia Tech, 2020-07-01)In many source waters across the United States (US), chloride levels are increasing and this change could be problematic for galvanized iron pipe (GIP) installed in consumers' homes and buildings. The higher levels of chloride might increase the rate of galvanic corrosion between the sacrificial zinc coating and the underlying iron (steel) pipe. There are also concerns that the iron in GIP can accumulate lead on its surface from upstream lead service lines, occasionally causing high lead in water from GIP during scale sloughing and associated red water events. The role of high chloride and potential mitigation strategies by orthophosphate and alkalinity on galvanic iron-zinc corrosion in GIP were examined by using new iron and zinc wires, and complementary studies with 85-year-old harvested GIP coupons from the Washington Suburban Sanitary Commission (WSSC). Sequential samplings on a constructed pilot-scale test rig with copper – lead – GIP ¬– brass meter configuration were used to evaluate lead source fingerprinting methods (metal co-occurrence, correlating the plumbing configuration to sample profiling data, and evaluation of lead isotope ratios) and role of flow rate. As chloride concentration increased from 2.6 to 554 mg/L, galvanic current and weight loss of sacrificial zinc increased by about an order of magnitude. Iron leaching also increased by 4.4 times as chloride levels increased by a factor of 12 in WSSC modified water to simulate actual road salt runoff events. Increased orthophosphate or alkalinity could at least partly counter the adverse effects of chloride, as the average iron concentration decreased by 43% as orthophosphate level increased from 3.8 to 11.2 mg/L as P, and average iron concentrations decreased by 32% as alkalinity increased from 50 to 90 mg/L as CaCO3. Applying fingerprinting methods on sequential samples has the potential to determine whether premise plumbing contains GIP and/or lead pipe. Specifically, the metal co-occurrence fingerprinting technique was successful in identifying the location of GIP by the detection of low-level cadmium, and the lead isotope ratio fingerprinting technique was fairly successful in identifying lead pipe. Additionally, our study found that GIP was not contaminated by an upstream lead pipe after five months of conditioning; hence, water discoloration (iron level > 400 ppb) does not always indicate lead problems from GIP. However, with longer exposure of GIP to lead pipe, the magnitude of the problem might increase. As flow rate increased from 0.9 to 2.4 GPM, the median particulate iron release increased by 3.3 times, and the median particulate lead release (>83% particulate lead) increased by 4.9 times.
- Sorption of Boron and Chromium Onto Solids of Environmental Significance: Implications for Sampling and Removal in Water TreatmentParks, Jeffrey L. (Virginia Tech, 2005-09-06)The chemistry, analysis, treatment, and occurrence of boron and chromium are of high interest since they are under consideration for revised MCLs in potable water. As a starting point to guide regulatory decision-making, a comprehensive review of boron in relation to potable water was undertaken. That work demonstrated that there were not proven cost-effective options for boron treatment. In preparation for a national survey of boron and chromium occurrence, it was discovered that existing analytical protocols sometimes '"missed" much of the total chromium that was present in water. It was determined that this was due to incomplete dissolution of particulates during routine Standard Method analysis of drinking water at pH 2.0. A more rigorous hydroxylamine digestion was developed and applied to circumvent this limitation. In relation to treatment, it was determined that sodium carbonate softening at pH 10.3 is a viable method of removing various inorganic contaminants including chromium from drinking water sources. The nationwide survey revealed that removals varied widely and were dependent on solution composition. Median removal of chromium was 92%. Linear and nonlinear empirical models were fit to crudely estimate the removal of various contaminants in the presence of other elements that are typically removed in the softening process (i.e. calcium, magnesium, silicon, iron, and aluminum). Boron was removed to a much lesser extent (median removal 2%) in this study, consistent with the general result of the literature review that enhanced treatments will be required for this contaminant. Modified precipitative softening was examined as a potentially attractive option to remove boron from natural waters. It was discovered that in some cases when magnesium and silicon were present, and if the pH was 10.8 ± 0.2, very high levels of boron removal (up to 90%) could be achieved versus 10% typically observed for conventional processes. This can be exploited to remove boron in waters naturally containing high levels of magnesium and silicon, or by adding supplemental amounts of either magnesium or silicon when one constituent is deficient.
- Tracking reduction of water lead levels in two homes during the Flint Federal EmergencyMantha, Anurag; Tang, Min; Pieper, Kelsey J.; Parks, Jeffrey L.; Edwards, Marc A. (2020-05-01)A Federal Emergency was declared in Flint, MI, on January 16, 2016, 18-months after a switch to Flint River source water without phosphate corrosion control. Remedial actions to resolve the corresponding lead in water crisis included reconnection to the original Lake Huron source water with orthophosphate, implementing enhanced corrosion control by dosing extra orthophosphate, a "Flush for Flint" program to help clean out loose leaded sediment from service lines and premise plumbing, and eventually lead service line replacement. Independent sampling over a period of 37 months (January 2016eFebruary 2019) was conducted by the United States Environmental Protection Agency and Virginia Tech to evaluate possible human exposure via normal flow (2e3 L/min) sampling at the cold kitchen tap, and to examine the status of loose deposits from the service line and the premise plumbing via high-velocity flushing (12e13 L/min) from the hose bib. The sampling results indicated that high lead in water persisted for more than a year in two Flint homes due to a large reservoir of lead deposits. The effects of a large reservoir of loose lead deposits persisted until the lead service line was completely removed in these two anomalous homes. As water conservation efforts are implemented in many areas of the country, problems with mobile lead reservoirs in service lines are likely to pose a human health risk.
- Understanding Practical Limitations of Lead Certified Point of Use (POU) FiltersRouillier, Rusty Jordan (Virginia Tech, 2020-07-27)There has been a recent increase in the adoption of point-of-use (POU) household water filters as an alternative to untreated tap water or bottled water. POU filters certified for lead removal have recently been distributed by the hundreds of thousands in communities amid water lead crises, as a temporary solution to protect consumers from elevated water lead levels. This thesis rigorously examines the efficacy of POU lead certified filters in removing lead under a wide range of conditions, and evaluates premature clogging due to iron and associated impacts on the cost analysis of using filters instead of bottled water. In testing ten brands of POU devices against up to four different waters for lead removal, most devices consistently removed lead to below the 5 µg/L FDA bottled water standard. However, several failures were documented, including manufacturing flaws, premature clogging, and inconsistency between duplicate filters. When waters containing more difficult to treat lead particulates were synthesized, treated water often had lead concentrations greater than the 5 µg/L bottled water standard and sometimes were even over the 15 µg/L EPA action level. In some cases, less than 50% of the particulate lead was removed by the filter, thereby replicating some problems with these devices identified in the field. While POUs usually reduced water lead concentrations by at least 80%, a combination of manufacturing issues and difficult to treat waters can cause treated water to exceed expectations. Consumers often purchase POU devices to remove particles and lead in waters that also contain high iron, prompting studies to examine the role of iron on filter performance. When we exposed two brands of pour-through POUs to waters with both high lead and iron, lead removal performance was generally not compromised, as treated water typically had lead concentrations less than 5 µg/L. One case was observed in which lead passed through a set of filters at high levels in association with iron, confirming expectations that in some waters iron could cause formation of lead particulates that are difficult to remove. High levels of iron sometimes rapidly clogged the POU filters, preventing them from reaching their rated capacity and increasing operational costs and time to filter water. Specifically, 50% (3/6) of the filters tested clogged prematurely at an iron concentration of 0.37 mg/L, 66% (4/6) at 1 mg/L and 100% (6/6) at 20 mg/L. A cost analysis for POUs vs. bottled water demonstrated that in waters with higher iron, store-brand bottled water was often the more cost-effective option, especially when iron levels were significantly higher than the EPA Secondary Maximum Contaminant Level (0.3 mg/L). The lower costs of bottled water in these situations was even more apparent if consumer time was factored into the analysis.