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Gao Y, Trueman BF, Gagnon GA. Early phase effects of silicate and orthophosphate on lead (Pb) corrosion scale development and Pb release. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022; 321:115947. [PMID: 35977436 DOI: 10.1016/j.jenvman.2022.115947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/30/2022] [Accepted: 08/02/2022] [Indexed: 06/15/2023]
Abstract
Orthophosphate is widely used to control lead (Pb) release in drinking water distribution systems, but phosphorus addition is not sustainable. Alternative corrosion control treatments are needed, and sodium silicate is one possibility. Here, pre-corroded Pb coupons-with and without free chlorine-were used to examine early-phase corrosion scale development after silicate addition, with orthophosphate as a reference corrosion inhibitor. Scale development was evaluated in terms of total Pb release, phase transformation, electrochemical impedance, morphological changes, Pb dissolution kinetics, and short-term Pb-Cu galvanic corrosion. Elevated Pb release occurred for approximately one month after silicate addition, and total Pb release peaked at 1968.1 μg/L and 1176.9 μg/L from systems with and without free chlorine, respectively. In contrast, orthophosphate-treated coupons exhibited fewer, less pronounced spikes in Pb release. By day 354, the median total Pb release from orthophosphate-treated coupons with and without free chlorine had decreased to 3.7 and 5.0 μg/L, respectively, while the median total Pb release from corresponding silicate-treated coupons was much higher, at 44.9 μg/L and 34.3 μg/L. Calcium lead apatite (Ca0.56Pb3.77(PO4)3OH0.67) was identified in orthophosphate-treated scales, with hydroxylpyromorphite (Pb5(PO4)3OH) present in the absence of free chlorine. Plattnerite occurred on coupons in all chlorinated systems. Pb silicate compounds were not detected, but Ca2SiO4 and Na2Ca2(SiO3)3 were identified by X-ray powder diffraction. The charge transfer: film resistance ratio characterizing the orthophosphate-treated coupons decreased slowly while that of the silicate-treated coupons increased after silicate was added. These variations suggest orthophosphate provided better corrosion control than silicate did. Silicate treatment generally caused degradation of the top Pb scale layer, resulting in elevated Pb release, while orthophosphate encouraged the growth of more structured, generally thicker, corrosion scales that were effective in limiting Pb release.
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Affiliation(s)
- Yaohuan Gao
- School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, 28 Xianning West Road, Xi'an, Shaanxi, 710049, PR China; Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada.
| | - Benjamin F Trueman
- Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Graham A Gagnon
- Department of Civil and Resource Engineering, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, B3H 4R2, Canada
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Impacts of orthophosphate-polyphosphate blends on the dissolution and transformation of lead (II) carbonate. Sci Rep 2022; 12:17885. [PMID: 36284172 PMCID: PMC9596708 DOI: 10.1038/s41598-022-22683-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 10/18/2022] [Indexed: 01/20/2023] Open
Abstract
Orthophosphate-polyphosphate blends are commonly used to control lead release into drinking water, but little is known about how they interact with lead corrosion scale. Conventional corrosion control practice assumes that orthophosphate controls lead release by forming insoluble Pb-phosphate minerals, but this does not always occur, and under certain conditions, phosphate blends may increase lead release. Here, we used continuously-stirred tank reactors to compare orthophosphate-polyphosphate blends with orthophosphate on the basis of lead (II) carbonate dissolution and transformation at environmentally relevant phosphate concentrations. Three model polyphosphates-tripoly-, trimeta- and hexametaphosphate-were used. Hexametaphosphate was the strongest complexing agent (1.60-2.10 molPb/molPolyphosphate), followed by tripolyphosphate and trimetaphosphate (1.00 and 0.07 molPb/molPolyphosphate, respectively. At equivalent orthophosphate and polyphosphate concentrations (as P), orthophosphate-trimetaphosphate had minimal impact on lead release, while orthophosphate-tripolyphosphate increased dissolved lead. Orthophosphate-hexametaphosphate also increased dissolved lead, but only over a 24-h stagnation. Both orthophosphate-tripolyphosphate and orthophosphate-hexametaphosphate increased colloidal lead after 24-h. Increasing the concentrations of hexameta- and tripoly-phosphate increased dissolved lead release, while all three polyphosphates inhibited the formation of hydroxypyromorphite and reduced the phosphorus content of the resulting lead solids. We attributed the impacts of orthophosphate-polyphosphates to a combination of complexation, adsorption, colloidal dispersion, polyphosphate hydrolysis, and lead mineral precipitation.
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Li B, Trueman BF, Rahman MS, Gagnon GA. Controlling lead release due to uniform and galvanic corrosion - An evaluation of silicate-based inhibitors. JOURNAL OF HAZARDOUS MATERIALS 2021; 407:124707. [PMID: 33341575 DOI: 10.1016/j.jhazmat.2020.124707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/03/2020] [Accepted: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Silicates have been added to drinking water for decades, both to sequester iron/manganese and as a corrosion control treatment for lead. But the mechanisms by which they might act to limit lead release are not well understood. We evaluated the effects of two silicate formulations on lead release due to uniform and galvanic corrosion over a wide range of pH and dissolved inorganic carbon concentrations. We compared these results to better-characterized systems, with added ortho- or polyphosphate and in an inhibitor-free control. Independent of pH, silicates did not consistently mitigate lead release due to either uniform or galvanic corrosion. Furthermore, lead carbonates appeared to determine lead solubility in the presence of sodium silicate. While silicate treatment did promote the formation of a nanometer-thick silicon layer on lead and a decrease in crystallite size at the scale surface, these changes did not inhibit lead release. But unlike polyphosphate-which is known to form soluble complexes with lead and disperse particulate metals-high ratio silicate did not exacerbate lead release. Metasilicate did exacerbate lead release, especially at pH 7 and 5 mg DIC/L; this suggests that silicate formulation may have an important effect on the dispersion of lead-rich particles.
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Affiliation(s)
- Bofu Li
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia B3H 4R2, Canada.
| | - Benjamin F Trueman
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia B3H 4R2, Canada
| | - Mohammad Shahedur Rahman
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia B3H 4R2, Canada; Civil Engineering Department, College of Engineering, Al Imam Mohammad Ibn Saud Isalamic University, Riyadh, Saudi Arabia
| | - Graham A Gagnon
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia B3H 4R2, Canada
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Sciuto EL, Laganà P, Filice S, Scalese S, Libertino S, Corso D, Faro G, Coniglio MA. Environmental Management of Legionella in Domestic Water Systems: Consolidated and Innovative Approaches for Disinfection Methods and Risk Assessment. Microorganisms 2021; 9:577. [PMID: 33799845 PMCID: PMC8001549 DOI: 10.3390/microorganisms9030577] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/08/2021] [Accepted: 03/09/2021] [Indexed: 12/31/2022] Open
Abstract
Legionella is able to remain in water as free-living planktonic bacteria or to grow within biofilms that adhere to the pipes. It is also able to enter amoebas or to switch into a viable but not culturable (VBNC) state, which contributes to its resistance to harsh conditions and hinders its detection in water. Factors regulating Legionella growth, such as environmental conditions, type and concentration of available organic and inorganic nutrients, presence of protozoa, spatial location of microorganisms, metal plumbing components, and associated corrosion products are important for Legionella survival and growth. Finally, water treatment and distribution conditions may affect each of these factors. A deeper comprehension of Legionella interactions in water distribution systems with the environmental conditions is needed for better control of the colonization. To this purpose, the implementation of water management plans is the main prevention measure against Legionella. A water management program requires coordination among building managers, health care providers, and Public Health professionals. The review reports a comprehensive view of the state of the art and the promising perspectives of both monitoring and disinfection methods against Legionella in water, focusing on the main current challenges concerning the Public Health sector.
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Affiliation(s)
- Emanuele Luigi Sciuto
- Azienda Ospedaliero Universitaria Policlinico “G. Rodolico-San Marco”, Via Sofia 78, 95123 Catania, Italy;
| | - Pasqualina Laganà
- Regional Reference Laboratory of Clinical and Environmental Surveillance of Legionellosis, Messina, Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Torre Biologica 3p, AOU ‘G. Martino, Via C. Valeria, s.n.c., 98125 Messina, Italy;
| | - Simona Filice
- Istituto per la Microelettronica e Microsistemi–Consiglio Nazionale delle Ricerche (CNR-IMM), Ottava Strada 5, 95121 Catania, Italy; (S.F.); (S.S.); (S.L.); (D.C.)
| | - Silvia Scalese
- Istituto per la Microelettronica e Microsistemi–Consiglio Nazionale delle Ricerche (CNR-IMM), Ottava Strada 5, 95121 Catania, Italy; (S.F.); (S.S.); (S.L.); (D.C.)
| | - Sebania Libertino
- Istituto per la Microelettronica e Microsistemi–Consiglio Nazionale delle Ricerche (CNR-IMM), Ottava Strada 5, 95121 Catania, Italy; (S.F.); (S.S.); (S.L.); (D.C.)
| | - Domenico Corso
- Istituto per la Microelettronica e Microsistemi–Consiglio Nazionale delle Ricerche (CNR-IMM), Ottava Strada 5, 95121 Catania, Italy; (S.F.); (S.S.); (S.L.); (D.C.)
| | - Giuseppina Faro
- Azienda Sanitaria Provinciale di Catania, Via S. Maria La Grande 5, 95124 Catania, Italy;
| | - Maria Anna Coniglio
- Azienda Ospedaliero Universitaria Policlinico “G. Rodolico-San Marco”, Via Sofia 78, 95123 Catania, Italy;
- Regional Reference Laboratory of Clinical and Environmental Surveillance of Legionellosis, Catania, Department of Medical and Surgical Sciences and Advanced Technologies “G.F. Ingrassia”, University of Catania, Via Sofia 87, 95123 Catania, Italy
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Li B, Trueman BF, Munoz S, Locsin JM, Gagnon GA. Impact of sodium silicate on lead release and colloid size distributions in drinking water. WATER RESEARCH 2021; 190:116709. [PMID: 33341036 DOI: 10.1016/j.watres.2020.116709] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/20/2020] [Accepted: 11/28/2020] [Indexed: 06/12/2023]
Abstract
Sodium silicates have been used in drinking water treatment for decades as sequestrants and corrosion inhibitors. For the latter purpose they are poorly understood, which presents a potential public health risk. We investigated a common sodium silicate formulation as a treatment for lead release and compared it to orthophosphate, a well-established lead corrosion control treatment. We also compared the size distributions of colloids generated in silicate and orthophosphate-treated systems using field flow fractionation with multielement detection. At a moderate dose of 24 mg SiO2/L, sodium silicate yielded a median lead release of 398 µg/L, while orthophosphate yielded 67 µg Pb/L. At an elevated dose of 48 mg SiO2/L, sodium silicate dispersed corrosion scale in cast iron pipe sections and lead service lines, resulting in a substantial release of colloidal iron and lead. In the silicate-treated system, a silicon-rich coating occurred at the lead-water interface, but lead carbonate remained the major corrosion product and appeared to control lead levels. These data suggest that, as a corrosion control treatment for lead, sodium silicate is inferior to orthophosphate in circumneutral pH water with low alkalinity. And, as with polyphosphate, excess silicate can be highly detrimental to controlling lead release.
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Affiliation(s)
- Bofu Li
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia, Canada B3H 4R2
| | - Benjamin F Trueman
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia, Canada B3H 4R2
| | - Sebastian Munoz
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia, Canada B3H 4R2
| | - Javier M Locsin
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia, Canada B3H 4R2
| | - Graham A Gagnon
- Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, 1360 Barrington St., Halifax, Nova Scotia, Canada B3H 4R2.
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Jurgens BC, Parkhurst DL, Belitz K. Assessing the Lead Solubility Potential of Untreated Groundwater of the United States. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3095-3103. [PMID: 30835445 DOI: 10.1021/acs.est.8b04475] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In the U.S., about 44 million people rely on self-supplied groundwater for drinking water. Because most self-supplied homeowners do not treat their water to control corrosion, drinking water can be susceptible to lead (Pb) contamination from metal plumbing. To assess the types and locations of susceptible groundwater, a geochemical reaction model that included pure Pb minerals and solid solutions of calcite (Ca xPb1- xCO3) and apatite [Ca xPb5-x(PO4)3(OH; Cl; F)] was developed to estimate the lead solubility potential (LSP) for over 8300 untreated groundwater samples collected from domestic and public-supply sites between 2000 and 2016 in the U.S. The LSP is the calculated amount of Pb metal that could dissolve at 25 °C before a Pb-bearing mineral precipitates. About 33% of untreated groundwater samples had LSP greater than 15 μg/L-the USEPA action level for dissolved plus particulate forms of Pb. Five percent of samples had high LSP (above 300 μg/L) and tended to occur in the eastern and southeastern U.S. Measured Pb concentrations above 15 μg/L were rarely detected (<1%) but always coincided with high LSP values. Future work will provide a better understanding of the relation between water chemistry, Pb-mineral formation, and dissolved Pb concentrations in tap water.
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Affiliation(s)
- Bryant C Jurgens
- U.S. Geological Survey , California Water Science Center , Sacramento , California 95819 , United States
| | - David L Parkhurst
- U.S. Geological Survey , Water Mission Area, Scientist Emeritus , Lakewood , Colorado 80225 , United States
| | - Kenneth Belitz
- U.S. Geological Survey , National Water Quality Assessment Project , Northborough , Massachusetts 01532 , United States
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Lytle DA, Schock MR, Leo J, Barnes B. A Model for Estimating the Impact of Orthophosphate on Copper in Water. ACTA ACUST UNITED AC 2018; 110:E1-E15. [PMID: 32636529 DOI: 10.1002/awwa.1109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The nature of copper phosphate minerals in drinking water distribution systems has remained largely unsolved despite being an important link to reducing cuprosolvency. Chemical equilibrium modeling has also largely failed to accurately predict soluble copper in the presence of orthophosphate. The objective of this work was to develop and validate an empirical copper solubility model that considered pH, dissolved inorganic carbon (DIC), and orthophosphate from a series of bench-scale copper precipitation experiments. An empirical model was constructed that allows for the determination of copper levels in a system given pH, DIC, and orthophosphate data. The predictive reliability of this model was assessed by evaluating a collection of cuprosolvency data from two decades of research and field observations and water treatment reports. The tests yielded a firm correlation between predicted and observed copper levels attested by a regression coefficient of 0.86 for a total of 851 observations.
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Affiliation(s)
- Darren A Lytle
- US Environmental Protection Agency, ORD, NRMRL, WSWRD, TTEB, Cincinnati, Ohio
| | - Michael R Schock
- US Environmental Protection Agency, ORD, NRMRL, WSWRD, TTEB, Cincinnati, Ohio
| | - Jordan Leo
- College of Engineering and Applied Sciences, Chemical Engineering, University of Cincinnati, Cincinnati, Ohio
| | - Benjamin Barnes
- Department of Natural Resources, Chemistry, University of Maryland Eastern Shore, Princess Anne, Md
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Masters S, Parks J, Atassi A, Edwards MA. Distribution system water age can create premise plumbing corrosion hotspots. ENVIRONMENTAL MONITORING AND ASSESSMENT 2015; 187:559. [PMID: 26251058 DOI: 10.1007/s10661-015-4747-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 07/14/2015] [Indexed: 06/04/2023]
Abstract
Cumulative changes in chemical and biological properties associated with higher "water age" in distribution systems may impact water corrosivity and regulatory compliance with lead and copper action levels. The purpose of this study was to examine the effects of water age and chemistry on corrosivity of various downstream premise plumbing pipe materials and configurations using a combination of controlled laboratory studies and a field survey. Examination of lead pipe, copper pipe with lead solder, and leaded brass materials in a replicated lab rig simulating premise plumbing stagnation events indicated that lead or copper release could increase as much as ∼440 % or decrease as much as 98 % relative to water treatment plant effluent. In field studies at five utilities, trends in lead and copper release were highly dependent on circumstance; for example, lead release increased with water age in 13 % of cases and decreased with water age in 33 % of conditions tested. Levels of copper in the distribution system were up to 50 % lower and as much as 30 % higher relative to levels at the treatment plant. In many cases, high-risks of elevated lead and copper did not co-occur, demonstrating that these contaminants will have to be sampled separately to identify "worst case" conditions for human exposure and monitoring.
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Affiliation(s)
- Sheldon Masters
- Via Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA,
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Lin N, Torrents A, Davis AP, Zeinali M, Taylor FA. Lead corrosion control from lead, copper‐lead solder, and brass coupons in drinking water employing free and combined chlorine. ACTA ACUST UNITED AC 2008. [DOI: 10.1080/10934529709376583] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Viraraghavan T, Subramanian KS, Rao BV. Impact of household plumbing fixtures on drinking water quality — a review. ACTA ACUST UNITED AC 2007. [DOI: 10.1080/00207239908711234] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Cardew PT. Development of a convective diffusion model for lead pipe rigs operating in laminar flow. WATER RESEARCH 2006; 40:2190-200. [PMID: 16704873 DOI: 10.1016/j.watres.2006.03.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2004] [Revised: 11/09/2005] [Accepted: 03/22/2006] [Indexed: 05/09/2023]
Abstract
As part of achieving lower lead standards water undertakers are utilising lead pipe rigs to quantify the benefit of treatment measures. A convective diffusion model is developed for lead pipe rigs operating in laminar flow, and applied to the three operating steps of flushing, sampling and stagnation. The model is used to determine the appropriate time-scales for each stage, and the sensitivity of the measure to variations in flow-rate. In contrast to rigs operating in turbulent flow the average lead observed leaving the pipe and that in the pipe, after a period of stagnation, are substantially different. Equations are derived for both, and take into account the residual distribution of lead left in the pipe after flushing. It is shown that the lead concentration observed leaving the pipe is well approximated by a single exponential term in contrast to the concentration within the pipe. Predictions are made on the residual lead concentration that can be achieved through flushing, and its dependence on flow-rate. The relevance of the laminar flow model to that in domestic lead pipes is discussed.
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Affiliation(s)
- P T Cardew
- United Utilities plc, Strategy & Planning, Thirlmere House, Lingley Mere Business Park, Lingley Green Avenue, Great Sankey, Warrington, Cheshire WA5 3LP, UK.
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Hozalski RM, Esbri-Amador E, Chen CF. Comparison of stannous chloride and phosphate for lead corrosion control. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/j.1551-8833.2005.tb10847.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Cantor AF, Denig-Chakroff D, Vela RR, Oleinik MG, Lynch DL. Use of polyphosphate in corrosion control. ACTA ACUST UNITED AC 2000. [DOI: 10.1002/j.1551-8833.2000.tb08820.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Edwards M, Jacobs S, Dodrill D. Desktop guidance for mitigating Pb and Cu corrosion by-products. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/j.1551-8833.1999.tb08635.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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