Understanding Failure Modes of NSF/ANSI 53 Lead-Certified Point-of-Use Pitcher and Faucet Filters

Purchase, Jeannie M.; Rouillier, Rusty; Pieper, Kelsey J.; Edwards, Marc

doi:10.1021/acs.estlett.0c00709

Cited by 20 publications

(19 citation statements)

References 10 publications

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“…The NSF/ANSI 53 certified POU filters may face underperformance under certain conditions. ,− Recently, a field investigation in Newark found that Pb phosphate nanoparticles (diameter: <0.1 μm) can penetrate properly installed and functional POU filters with total Pb concentrations in the filtered water as high as 45 μg/L . Moreover, the NSF/ANSI 53 certification protocol challenges filters by using a Pb(NO 3 ) 2 solution to develop Pb carbonates and oxides that are 0.1–1.2 μm in size .…”

Section: Introductionmentioning

confidence: 99%

Lead Phosphate Particles in Tap Water: Challenges for Point-of-Use Filters

Pan

Johnson

Giammar

2021

Environ. Sci. Technol. Lett.

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To lower Pb concentrations in tap water, water systems implement corrosion control treatment that often involves the addition of orthophosphate. Because NSF/ANSI 53 (2018) certified point-ofuse (POU) filters can remove Pb from tap water to less than 10 μg Pb/ L, they are often distributed in emergencies or as follow-up steps to lead service line removals or disturbances. While these filters are certified for the removal of both soluble and particulate lead, this study reported that Pb phosphate particles can penetrate POU filters under certain conditions. The small sizes and negative surface charges of suspended Pb phosphate particles make them more mobile through the solid block activated carbon media of POU filters. When tested using challenging water containing 150 μg Pb/L, 2 mM ionic strength (IS), and no hardness at pH 7.0, 41% of the Pb passed through the POU filters. However, when IS was increased to 50 mM or Ca was increased to 0.5 mM, the amount of Pb penetrating the POU filters decreased to 32% and 17%, respectively. Adsorption of Ca onto Pb phosphate particles and high IS promotes aggregation and enhances POU filter performance.

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Section: Introductionmentioning

confidence: 99%

Lead Phosphate Particles in Tap Water: Challenges for Point-of-Use Filters

Pan

Johnson

Giammar

2021

Environ. Sci. Technol. Lett.

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“…Recent studies have shown that point-of-use filters may be poorly suited to removing highly dispersed colloidal lead. ,− Given the dispersive properties of sodium silicates, a potential risk of silicate treatment is the dispersion of lead-rich colloids. This effect is analogous to the negative side effects of polyphosphate (another common class of sequestrants) , and sometimes even orthophosphate. ,,, The higher total lead concentrations due to silicate that have been reported in some previous studies ,, maybe due in part to dispersion (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Effectiveness of Sodium Silicates for Lead Corrosion Control: A Critical Review of Current Data

Trueman

Doré

et al. 2021

Environ. Sci. Technol. Lett.

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Orthophosphate is commonly used to control lead release to drinking water, but it is a potential source of nutrient pollution and can increase the concentration of particulate and colloidal lead. Given these drawbacks, there is considerable interest in alternative corrosion control treatments. While less common than orthophosphate, sodium silicate is recognized as a treatment for controlling lead release to drinking water. But there is no consensus in the scientific literature as to whether it is effective. Here, we conduct a data summary of the peer-reviewed literature pertaining to silicate-based corrosion control of lead. We find that silicate treatment generally accompanied higher lead release than the equivalent (pH-matched) system without sodium silicate (0.5−21.5 times higher). Moreover, silicate treatment was inferior to orthophosphate treatment; sodium silicate accompanied 1.0−65 times more lead release than the equivalent orthophosphatetreated system. Sodium silicate's positive effect on pH, then, appears to be the main driver of lead release control. While it is possible that under some circumstances silicate treatment promotes formation of a solid phase that either limits equilibrium solubility or slows lead release, the mechanism has not been described precisely.

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“…NSF/ANSI 53 certified POU filters have been distributed in cities facing lead-in-water crises, such as Washington, DC. Flint, MI, Newark, NJ, University Park, IL, and Benton Harbor, MI. , However, field sampling and lab tests have found conditions at which POU filters did not work well. , In particular high concentrations of particulate lead (1–45 μg Pb/L) were observed in the effluent of POU filters in Newark, NJ . When challenged in the laboratory with water containing lead phosphate particles (150 μg Pb/L, pH 7, and 2 mM ionic strength), these filters only removed 55% at low hardness .…”

Section: Challengesmentioning

confidence: 99%