Browsing by Author "Tang, Min"

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    Evaluating Water Lead Levels During the Flint Water Crisis
    Pieper, 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.
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    In-Situ Remediation of Small Leaks in Water Pipes: Impacts of Water Chemistry, Physical Parameters and the Presence of Particles
    Tang, Min (Virginia Tech, 2017-03-02)
    Aging and leaking water infrastructure wastes water resources and creates public health risks. Upgrading of potable water systems represents a large financial burden for water utilities and private property owners. The conventional approaches of repair, rehabilitation and replacement are very effective, but will take decades to implement even if a financial commitment to do so was made immediately. A novel approach of in-situ remediation of leaks, achieved by harnessing the ability of water or pipe to repair leaks via clogging, could potentially reduce leak rates and extend the lifetime of existing infrastructure at relatively low cost and inconvenience. Physical clogging, precipitation and metallic corrosion were identified as major mechanisms of in-situ leak remediation in potable water pipelines. Autogenous repair (i.e., self-repair without added particles) of small leak-holes (150–"1000 μm) in copper and iron was validated in the laboratory at water pHs of 3.0–11.0, operating water pressures of 20–60 psi, upward and downward leak orientations, and for a range of water chemistries. In bench scale experiments, the time to repair of iron pipe leaks increased with leak size to the power of 0.89–1.89, and decreased with pipe wall thickness to the power of -1.9 to -1.0. The time to repair of copper pipe leaks increased with water pressure to the power of 1.7. Additionally, the waters with a higher DO and corrosivity as measured by RSI, significantly decreased the time to repair of carbon steel 400 μm leaks by 50–70%. The presence of chlorine dioxide significantly increased the fraction of repaired 200 μm copper pipe leaks by 3 times when compared to the control without any disinfectant. In the building scale study, the fraction of repaired iron pipe leaks decreased with the logarithmic leak size with a slope of -0.65 after one-year duration of experiments, while leak orientation and water pressure were not influential in time to or likelihood of repair for iron pipe leaks. Addition of calcium carbonate particles (~8.8 μ]m), silica particles (~29 μm) and wood ash particles (~160 μm) in Blacksburg, VA tap water at a water pressure of 10 psi increased the fraction of remediated iron pipe leaks of 280–1000 μm diameter sizes. Although the control condition with no added particles for 58 days resulted in remediation of 0/12 leaks, remediation rate increased to 1/12 with calcium carbonate particles, to 10/12 with silica particles and to 10/12 with wood ash particles. Leak size and particle size played an important role in controlling the remediation success rate. The strength of the in-situ leak repair was sometimes very strong and resilient. The sealing materials of leak-holes repaired at 20–60 psi could sometimes withstand a 100 psi water pressure without failure, demonstrating the potential of the approach to sustain aging and leaking infrastructure. In-situ leak repair can also occur naturally, and the success rate might be unintentionally altered by adjustment of chemistry or treatments that decrease or increase particulates.
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    Lead release to potable water during the Flint, Michigan water crisis as revealed by routine biosolids monitoring data
    Roy, Siddhartha; Tang, Min; Edwards, Marc A. (2019-09-01)
    Routine biosolids monitoring data provides an independent and comprehensive means to estimate water lead release pre-, during and post-Flint Water Crisis (FWC). The mass of potable plumbing-related metals ( i.e., lead, cadmium, copper, nickel and zinc) in sewage biosolids strongly correlated with one another during the FWC (p < 0.05). A simple parametric regression model based on 90th percentile potable water lead measurements (WLL90) from five city-wide citizen science sampling efforts August 2015-August 2017 was strongly correlated to corresponding monthly lead mass in biosolids [Biosolids-Pb (kg) = 0.483 x WLL90 (mu g/L) + 1.79: R-2 = 0.86, p < 0.05]. Although total biosolids lead increased just 14% during the 18 months of the FWC versus the comparable time pre-FWC, 76% of that increase occurred in July -September 2014, and the corresponding percentage of Flint children under 6 years with elevated blood lead >= 5 mu g/dL (i.e., %EBL5) doubling from 3.45% to 6.61% in those same three months versus 2013 (p < 0.05). %EBL5 was not statistically higher during the remaining months of the FWC compared to preFWC or post-FWC. As expected, lead in biosolids during the FWC, when orthophosphate was not added, was moderately correlated with water temperature (R-2 = 0.30, p < 0.05), but not at other times pre- and post-FWC when orthophosphate was present. Tripling the orthophosphate dose post-FWC versus pre-FWC and some lead pipe removal, decreased lead in biosolids (and %EBLS) to historic lows (2016-2017 vs. 2012-2013; p < 0.05), supporting the effectiveness of these public health interventions in reducing childhood water lead exposure. (C) 2019 The Authors. Published by Elsevier Ltd.
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    Tracking reduction of water lead levels in two homes during the Flint Federal Emergency
    Mantha, 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.