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Effectiveness of point-of-use and pitcher filters at removing lead phosphate nanoparticles from drinking water
Citation:
Dore, E., C. Formal, C. Muhlen, D. Williams, S. Harmon, M. Pham, S. Triantafyllidou, AND D. Lytle. Effectiveness of point-of-use and pitcher filters at removing lead phosphate nanoparticles from drinking water. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 201:117285, (2021). https://doi.org/10.1016/j.watres.2021.117285
Impact/Purpose:
Orthophosphate (PO4) addition is a common corrosion control treatment used to lower lead (Pb) concentrations at the consumer’s tap by forming relatively insoluble Pb-phosphate (Pb-PO4) minerals. Some Pb-PO4 particles are characteristically very small mobile Pb-PO4 nanoparticles (i.e., 0.001-0.1 µm) and can form in water. Many water utilities distribute point-of-use (POU) and pitcher filters following Pb service line replacements, during distribution system upsets or when corrosion control treatment is not optimized. POU and pitcher filters must be NSF/ANSI-certified for Pb reduction (NSF/ANSI-53) through a test water containing large Pb carbonate particles (> 1 µm) and for particulates’ reduction (NSF/ANSI-42) through a test water that does not contain Pb. The objective of this study was to challenge six certified commercially available faucet-mounted POU (3) and pitcher (3) filters with Pb-PO4 nanoparticle aqueous suspensions. Target water quality parameters for the synthetic challenge water were 100 µg total Pb/L, pH 7.5, total inorganic carbon of 7 mg C/L, PO4 in excess of 3 mg PO4/L. Particle size ranged between 0.016 and 0.098 µm, based on scanning electron microscopy and dynamic light scattering analysis and represented 98.5% of total Pb. POU filters removed between 44.6 and 64.6% of total Pb and pitcher filters between 10.9 and 92.9%. Electron microscopy confirmed that Pb-PO4 nanoparticles passed through the filters. Interestingly, filtering the challenge water increased mean pH values from 7.5 up to 9.6 for one filter. Findings can inform future efforts to re-examine the synthetic Pb particulate waters used in POU and pitcher filter certification challenge tests.
Description:
Orthophosphate (PO4) addition is a common corrosion control treatment used to lower lead (Pb) concentrations at the consumer’s tap by forming relatively insoluble Pb-phosphate (Pb-PO4) minerals. Some Pb-PO4 particles are characteristically very small mobile Pb-PO4 nanoparticles (i.e., 0.001-0.1 µm) and can form in water. Many water utilities distribute point-of-use (POU) and pitcher filters following Pb service line replacements, during distribution system upsets or when corrosion control treatment is not optimized. POU and pitcher filters must be NSF/ANSI-certified for Pb reduction (NSF/ANSI-53) through a test water containing large Pb carbonate particles (> 1 µm) and for particulates’ reduction (NSF/ANSI-42) through a test water that does not contain Pb. The objective of this study was to challenge six certified commercially available faucet-mounted POU (3) and pitcher (3) filters with Pb-PO4 nanoparticle aqueous suspensions. Target water quality parameters for the synthetic challenge water were 100 µg total Pb/L, pH 7.5, total inorganic carbon of 7 mg C/L, PO4 in excess of 3 mg PO4/L. Particle size ranged between 0.016 and 0.098 µm, based on scanning electron microscopy and dynamic light scattering analysis and represented 98.5% of total Pb. POU filters removed between 44.6 and 64.6% of total Pb and pitcher filters between 10.9 and 92.9%. Electron microscopy confirmed that Pb-PO4 nanoparticles passed through the filters. Interestingly, filtering the challenge water increased mean pH values from 7.5 up to 9.6 for one filter. Findings can inform future efforts to re-examine the synthetic Pb particulate waters used in POU and pitcher filter certification challenge tests.
URLs/Downloads:
DOI: Effectiveness of point-of-use and pitcher filters at removing lead phosphate nanoparticles from drinking water
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