Assessing taste and visual perception of Mn(II) and Mn(IV) (PDF)
- Author(s): Sain, Amanda E.; Griffin, Ashley; Dietrich, Andrea M.
- Publications: Journal - American Water Works Association
- Issue Date: January 2014
- Volume / Number: 106, Number 1
- Page(s): E32-E40
- DOI: http://dx.doi.org/10.5942/jawwa.2014.106.0003
- Product Number: JAW_0079043
Non-Member Price: $0
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The US Environmental Protection Agency secondary maximum
contaminant level (SMCL) for manganese (Mn) is 0.05 mg/L,
reportedly because of bitter metallic taste, black-brown particles
in water, and black-brown discoloration of fixtures and laundry.
This study revisited visual and taste thresholds for Mn(II) and
Mn(IV) using one-in-five, one-in-three, and triangle tests for
concentrations from 0.005 to 506 mg/L. Results showed that
Mn(II) and Mn(IV) do not taste significantly different from
distilled water at 0.05 mg/L Mn. The population taste threshold
for Mn(II) from manganese sulfate is > 1,000 times the SMCL;
the threshold concentration is 75-100 mg/L Mn(II) and likely is
influenced by both sulfate and Mn(II) taste contribution. Aqueous
Mn(II) is colorless at 0.05 mg/L and remains visually undetectable
at concentrations as high as 506 mg/L; Mn(IV) is visually
detectable in water at concentrations as low as 0.005 mg/L.
Findings suggest that consumers cannot detect Mn(II)
concentrations above the SMCL by taste or sight and that bitter
and metallic descriptors for 0.05 mg/L Mn are unwarranted.
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