The effect of zinc orthophosphate and pH-alkalinity adjustment on metal levels leached into drinking water

Churchill, D M; Mavinic, Donald S.; Neden, Douglas G.; MacQuarrie, Doug

doi:10.1139/l99-047

Cited by 11 publications

(16 citation statements)

References 11 publications

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“…The concentrations of particulate Pb were highly variable even 100 days after the initial addition of phosphate (Figures S17–S19). A longer period for control of particulate Pb than dissolved Pb is consistent with previous studies. − Welter et al found that occasional high concentrations of particulate Pb persisted in pipe loops using harvested lead service lines even 5 months after phosphate dosing . Although particulate Pb concentrations were higher than dissolved concentrations, they did still decrease with sustained dosing of phosphate (Figure S18).…”

Section: Resultssupporting

confidence: 81%

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products

Bae

Mishrra

et al. 2020

Environ. Sci. Technol.

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The occurrence of aluminum in scales on lead pipes is common. This study aimed to identify factors that influence Al accumulation on oxidized lead surfaces and to determine whether the presence of Al impacts Pb release from corrosion products to water. Al accumulation and Pb release were monitored both with and without the addition of phosphate as a corrosion inhibitor. Pb coupons with corrosion scales were exposed to chlorinated water for up to 198 days to investigate Al accumulation and Pb release. Al accumulation was facilitated by Pb corrosion products, but its accumulation was inhibited by phosphate addition. During the study period, the formation of Al deposits did not affect Pb release when phosphate was absent. In an Al-free system, the addition of 1.0 mg/L phosphate (as P) lowered the dissolved Pb concentration below 1.0 μg/L. In a system containing 200 μg/L Al, the emergence of phosphate’s effect on Pb control was delayed, and the dissolved Pb concentration decreased but stabilized at a higher value (10–12 μg/L) than in the Al-free system. Phosphohedyphane (Ca2Pb3(PO4)3Cl) was formed in all phosphate-containing systems, and PbO2 was formed independent of phosphate addition. The effect of Al on Pb release was probably related to its influence on the composition and morphology of Pb-containing minerals on coupon surfaces. The laboratory study has unavoidable limitations in its ability to simulate all conditions in real lead service lines, but this study still highlights the importance of considering the influence of Al when designing Pb corrosion control strategies.

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Section: Resultssupporting

confidence: 81%

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products

Bae

Mishrra

et al. 2020

Environ. Sci. Technol.

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“…After elevated Pb concentrations are observed in tap water, a water system can follow several strategies to control Pb, including the addition of orthophosphate and replacement of LSLs. ,− Orthophosphate addition can lead to the formation of Pb phosphate solids, which have low solubilities and are beneficial for dissolved Pb control. , However, studies have reported that total Pb concentrations (dissolved and particulate lead) in tap water can remain high (>50 μg/L) for months after phosphate addition. − A pipe loop study using high pH and low dissolved inorganic carbon (DIC) water conditions found that lead concentrations did not consistently drop below 15 μg/L until several months after orthophosphate addition had begun, while dissolved lead concentrations decreased almost immediately and stayed low . A pipe loop study evaluating corrosion control treatment in the District of Columbia Water and Sewer Authority’s distribution system found that it took six months of phosphate addition before lead concentrations consistently dropped below 15 μg/L…”

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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“…20 to 50 mg/L as CaCO 3 ) in Auckland's water had induced concrete leaching in the distribution system, [23] a higher range of alkalinity was applied in this study. To that effect, sodium bicarbonate (NaHCO 3 ) was added to achieve concentrations of 100, 125, and 150 mg/L as CaCO 3 , respectively, while the control samples had an alkalinity of 20 mg/L as CaCO 3 . At each alkalinity level tested, the pH was subsequently adjusted to 7.0, 7.5, 8.0, and 9.0 by bubbling carbon dioxide gas into the water and was measured at 1-hr, 4-hr, 24-hr, 48-hr and 72-hr intervals.…”

Section: Bench-scale Experimentsmentioning

confidence: 99%

“…[2] From a health viewpoint, drinking water suppliers are concerned about corrosion of plumbing fittings, which may result in the staining of fixtures and expose consumers to heavy metal contamination caused by leaching from fittings. [3,4] In particular, lead has been recognized as a cumulative poison to the human body, which can cause irreversible damage to the nervous system and create neurological problems especially to infants and children. [5,6] To minimize such potential hazards to public health and infrastructure, the metal content in water supplies has been regulated by various authorities worldwide.…”

Section: Introductionmentioning

confidence: 99%

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Corrosion control in water supply systems: Effect of pH, alkalinity, and orthophosphate on lead and copper leaching from brass plumbing

Tam¹,

Elefsiniotis

2009

Journal of Environmental Science and Health, Part A

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This study explored the potential of lead and copper leaching from brass plumbing in the Auckland region of New Zealand. A five-month field investigation, at six representative locations, indicated that Auckland's water can be characterized as soft and potentially corrosive, having low alkalinity and hardness levels and a moderately alkaline pH. More than 90% of the unflushed samples contained lead above the maximum acceptable value (MAV) of 10 microg/L (New Zealand Standards). In contrast, the copper level of unflushed samples remained consistently below the corresponding MAV of 2 mg/L. Flushing however reduced sharply metal concentrations, with lead values well below the MAV limit. Generally, metal leaching patterns showed a limited degree of correlation with the variations in temperature, dissolved oxygen and free chlorine residual at all sampling locations. Furthermore, a series of bench-scale experiments was conducted to evaluate the effectiveness of pH and alkalinity adjustment, as well as orthophosphate addition as corrosion control tools regarding lead and copper dissolution. Results demonstrated that lead and copper leaching was predominant during the first 24 hr of stagnation, but reached an equilibrium state afterwards. Since the soluble fraction of both metals was small (12% for lead, 29% for copper), it is apparent that the non-soluble compounds play a predominant role in the dissolution process. The degree of leaching however was largely affected by the variations in pH and alkalinity. At pH around neutrality, an increase in alkalinity promoted metal dissolution, while at pH 9.0 the effect of alkalinity on leaching was marginal. Lastly, addition of orthophosphate as a corrosion inhibitor was more effective at pH 7.5 or higher, resulting in approximately 70% reduction in both lead and copper concentrations.

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The effect of zinc orthophosphate and pH-alkalinity adjustment on metal levels leached into drinking water

Cited by 11 publications

References 11 publications

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products

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

Corrosion control in water supply systems: Effect of pH, alkalinity, and orthophosphate on lead and copper leaching from brass plumbing

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