Which value represents the drinking water standard for NO3-N in mg/L?

Which value represents the drinking water standard for NO3-N in mg/L?

• A. 5 mg/L NO3-N
• B. 20 mg/L NO3-N
• C. 10 mg/L NO3-N
• D. 15 mg/L NO3-N

Answer: (C)

Nitrate drinking-water standards are expressed as nitrate-nitrogen (NO3-N) to reflect the amount of nitrogen present in the contaminant, since nitrogen input from fertilizers and manure is a primary source of nitrate in water. The value set for safe drinking water is 10 mg/L as NO3-N, chosen to protect vulnerable populations, especially infants, from methemoglobinemia. When the limit is given as NO3-N, the correct value is 10 mg/L. The other numeric options exceed or fall short of the established regulatory limit, which is why they aren’t correct in this context. If you ever see the standard written as nitrate (NO3-), the numeric value would be a different figure due to unit conversion, so it’s important to note the unit used.

Nitrate drinking-water standards are expressed as nitrate-nitrogen (NO3-N) to reflect the amount of nitrogen present in the contaminant, since nitrogen input from fertilizers and manure is a primary source of nitrate in water. The value set for safe drinking water is 10 mg/L as NO3-N, chosen to protect vulnerable populations, especially infants, from methemoglobinemia. When the limit is given as NO3-N, the correct value is 10 mg/L. The other numeric options exceed or fall short of the established regulatory limit, which is why they aren’t correct in this context. If you ever see the standard written as nitrate (NO3-), the numeric value would be a different figure due to unit conversion, so it’s important to note the unit used.